8

Module

Self-Study Modules on Tuberculosis

Contact 

Investigations for 

Tuberculosis

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention 

Division of Tuberculosis Elimination

Contact Investigations 

for Tuberculosis

U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES

Centers for Disease Control and Prevention

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention

Division of Tuberculosis Elimination

Atlanta, Georgia

2014

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Contents

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

New Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Introduction to TB Contact Investigations . . . . . . . . . . . . . . . . . 4

Systematic Approach to TB Contact Investigations . . . . . . . . 15

Assessment and Management of TB Contacts . . . . . . . . . . . . . 58

TB Contact Investigations in Congregate Settings . . . . . . . . . 71

Conducting Source Case Investigations . . . . . . . . . . . . . . . . . . . 76

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

Answers to Study Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

Case Study Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

Appendix For Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

1

Module 8—Contact Investigations for Tuberculosis 

Background

In this module, you will learn about tuberculosis (TB) contact investigations. 

Persons who have been exposed to a case* of infectious TB disease are known as TB contacts. A 

TB contact investigation is a TB control strategy used to identify, find, and assess TB contacts and 

provide appropriate treatment for latent TB infection (LTBI) or TB disease, if needed. Effective 

contact investigations interrupt the spread of TB in communities and help prevent outbreaks of TB. 

Guidelines for TB contact investigations and management of TB contacts were published in 2005. 

For more detailed information, please refer to the Centers for Disease Control and Prevention 

(CDC) Guidelines for the Investigation of Contacts of Persons with Infectious Tuberculosis, available 

from the CDC website (www.cdc.gov/tb). 

* Please note that throughout this module the term “case” will be used instead of “patient” to describe persons with TB disease. Although 

“case” may seem impersonal, the rationale for using it is to avoid confusion with contacts who may also be considered “patients” if they are 

found to have LTBI or TB disease.

Objectives

After working through this module, 

you will be able to 

1. Define a TB contact 

investigation.

2. State the goals of a TB 

contact investigation.

3. Describe the systematic 

approach to TB contact 

investigations.

4. Define a TB source case 

investigation. 

define

explain

describe

list
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Module 8—Contact Investigations for Tuberculosis 

New Terms

New terms introduced in this module are included below. Please refer to the Self-Study Modules 1–5

Glossary if you encounter unfamiliar terms related to TB that are not defined in the glossary below.

case—a person with suspected or confirmed 

TB disease; sometimes referred to as an index 

case or index patient

case conference—meetings at designated 

intervals for reviewing the treatment of 

TB patients currently under care. During a 

case conference, the case manager presents 

information to colleagues about the status of 

each case under medical care and the progress 

of the contact investigation.

congregate setting—a setting in which a 

group of persons reside, meet, or gather either 

for a limited or extended period of time in 

close physical proximity. Examples include 

prisons, nursing homes, schools, and homeless 

shelters.

contacts—persons exposed to someone 

with infectious TB disease, can include family 

members, roommates or housemates, close 

friends, coworkers, classmates, and others 

contact investigation—a systematic 

process to identify persons (contacts) who 

were exposed to someone with infectious 

TB disease; assess contacts for infection 

with M. tuberculosis and TB disease; and 

provide contacts with treatment for latent TB 

infection or TB disease, if necessary

degree of infectiousness—physical or 

environmental characteristics that can affect 

ability to transmit M. tuberculosis

exposure period—the timeframe during 

which a contact may have been infected with 

M. tuberculosis

field visit—visiting a TB case’s residence, 

congregate settings, and other places where 

the TB case spent time while infectious. A 

field visit can also be used to locate or meet 

contacts.

genotype—distinct genetic pattern of an 

organism 
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Module 8—Contact Investigations for Tuberculosis 

genotyping—a laboratory-based method that 

can determine the genetic pattern of the strain 

of M. tuberculosis that caused TB disease in a 

person 

index case—the initial TB case that prompts a 

contact investigation

infectious—refers to a disease that is capable 

of being spread; a person who has infectious 

TB disease expels droplets containing M. 

tuberculosis into the air when he or she coughs, 

sneezes, speaks, or sings 

infectious period—time during which a TB 

case is potentially capable of transmitting M. 

tuberculosis

location-based investigation—an approach 

for conducting contact investigations onsite at 

a location where the TB case spent time while 

infectious. The purpose is to identify and assess 

potential TB contacts at that location.

pre-interview phase—reviewing existing 

information about the TB case before the first 

interview; typically this is the first step in the 

systematic approach to contact investigation

prevalence of TB infection—the percentage of 

persons infected with M. tuberculosis within a 

defined population

priority contacts—contacts who are at most 

risk for TB infection or disease

proxy—a person interviewed in place of a TB 

case. Potential proxies include family members, 

close friends, or other persons who know the 

person well. A proxy is used if the TB case 

is deceased, physically or mentally unable to 

participate in interviews, very young, or unable 

to be located

proxy interview—an interview with persons 

(proxies) who are familiar with the TB case’s 

practices, habits, and behaviors

secondary case—an instance of TB after a 

known exposure, usually related to the index 

case in an investigation

secondary transmission—when any of the 

secondary case’s contacts are found to have 

latent TB infection or TB disease

source case—a person with TB disease who 

is responsible for transmitting M. tuberculosis

to another person or persons 

source case investigation—a method used 

to identify a source case; usually done when a 

young child is found to have TB disease 

TB genotyping information management 

system (TB GIMS)—a secure CDC-sponsored 

online national database of M. tuberculosis

genotyping and TB case information

tumor necrosis factor-alpha (TNFalpha) antagonists, inhibitors, or 

blockers—medications used to treat 

inflammatory or autoimmune diseases such as 

rheumatoid arthritis, Crohn’s disease, psoriatic 

arthritis, and juvenile rheumatoid arthritis 

window period—the time between the 

contact’s last exposure to the TB case and 

when a TST or IGRA can reliably detect 

infection with M. tuberculosis

window period prophylaxis—treatment for 

latent TB infection that is given to high-risk 

contacts who have an initial negative test result 

for TB infection less than 8 to 10 weeks after 

their last TB exposure
Module 8—Contact Investigations for Tuberculosis 

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Introduction to TB Contact Investigations

Conducting contact investigations is a priority for tuberculosis 

(TB) programs in the United States. The goals of a contact 

investigation are to successfully stop TB transmission and 

prevent future cases and outbreaks of TB disease. It is important 

to remember that every TB case started as a TB contact.

What is a TB Contact Investigation?

A TB contact investigation is a systematic process to

1. Identify persons (contacts) exposed to a person with 

infectious TB disease (a case)

2. Assess contacts for infection with M. tuberculosis and TB 

disease 

3. Provide appropriate treatment for contacts with latent TB 

infection (LTBI) or TB disease 

Who are TB Contacts? 

Contacts are persons who have shared airspace with a person 

with infectious TB disease. These persons may include 

household members, friends, coworkers, classmates, and others. 

During a contact investigation, public health investigators 

identify contacts by interviewing the TB case and visiting places 

where the case spent time while infectious. 

Why is it Important to Identify and 

Assess TB Contacts? 

It is important to quickly identify, find, and assess contacts for 

TB infection and disease. Approximately 1% of all TB contacts 

have TB disease at the time of the contact investigation and 

are in need of treatment. Additionally, about 20% to 30% of TB 

contacts are infected with M. tuberculosis and are at risk for 

developing TB disease if not diagnosed and treated for LTBI. 

The goals of a contact 

investigation are to 

successfully stop TB 

transmission and 

prevent future cases and 

outbreaks of TB disease.

Contacts are persons who 

have shared airspace 

with a person with 

infectious TB disease.
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Module 8—Contact Investigations for Tuberculosis 

Contacts infected with M. tuberculosis who are at particularly 

high risk for developing TB disease rapidly include

 Children younger than 5 years of age 

 Persons with weakened immune systems due to

 HIV infection

 Immunosuppressive therapy, including tumor necrosis 

factor-alpha (TNF-alpha) antagonists, prolonged 

use of high-dose adrenocorticosteroids, or medications 

received after organ transplantation 

Contacts who have either LTBI or TB disease should be offered 

the appropriate treatment unless there is a compelling reason 

not to do so (e.g., the contact has hepatitis or end-stage 

liver disease). For a contact investigation to be considered 

successful, contacts should complete treatment if they have 

LTBI or TB disease.

Who is Responsible for Conducting TB Contact 

Investigations?

In the United States, state and local health departments are 

legally responsible for the prevention and control of TB in their 

communities. Thus, they are accountable for ensuring contact 

investigations are performed for TB cases reported in their 

jurisdictions, even when patients are receiving care outside the 

health department. 

Although health departments are responsible for conducting 

contact investigations, some steps of a contact investigation 

may be given to persons or programs outside of the health 

department. For example, if transmission of M. tuberculosis

occurs at a healthcare facility, the contact investigation 

may include hospital epidemiologists and infection control 

professionals. Whenever contact investigation activities are 

delegated, the health department should work with those 

involved to ensure that the local policies and procedures are 

followed. 

For some contact investigations, there may be areas and 

programs involved that are not under the jurisdiction of 

state or local health departments. For example, some 

contact investigations may involve military bases, federal 

prisons, diplomatic missions, or American Indian or Alaska 

Native tribal reservations. If an area or program has its own 

healthcare system or TB control program, state and local health 

departments can offer technical consultation and support. 

For a contact investigation 

to be considered successful, 

contacts should complete 

treatment if they have 

LTBI or TB disease.

Health departments are 

accountable for ensuring 

contact investigations 

are performed for TB 

cases reported in their 

jurisdictions, even 

when patients are 

receiving care outside 

the health department. 

Whenever contact 

investigation activities 

are delegated, the 

health department 

should work with those 

involved to ensure that 

the local policies and 

procedures are followed.
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Module 8—Contact Investigations for Tuberculosis 

For sites without their own healthcare system or TB control 

program, agreements can be made with authorities about how 

to handle the public health response. In tribal areas, health 

departments should coordinate with both tribal leadership and 

the system that is providing healthcare to tribal members, such 

as the Indian Health Service (IHS) or tribally run healthcare 

systems.

The Centers for Disease Control and Prevention (CDC) is 

available to assist in the coordination of contact investigations 

that involve tribal jurisdictions, multiple jurisdictions, or 

international jurisdictions. 

Which TB Cases Require a Contact Investigation?

Cases with Infectious Forms of TB Disease

Confirmed TB Cases

A contact investigation is required for all confirmed cases that 

have infectious forms of TB disease (e.g., TB disease of the 

lungs, airways, or larynx). 

Suspect TB Cases

The contact investigation process should be started for persons 

suspected of having infectious TB disease, even before 

confirmation. This includes persons with positive sputum smears 

and a positive nucleic acid amplification test result. For persons 

with positive sputum smears and a negative nucleic acid 

amplification test result, a contact investigation is not indicated.

For suspect cases with negative sputum smears or sputum 

smears not performed, the contact investigation process 

should be started if the case has abnormal chest x-ray findings 

consistent with TB disease. 

For suspect cases with negative sputum smear results and no 

pulmonary cavities, a contact investigation should only be 

considered for certain circumstances, such as if the suspect was 

identified during an outbreak or source case investigation that 

included vulnerable or susceptible contacts. 

If it is later determined that the suspect case does not have 

infectious TB disease, the contact investigation should be 

stopped. 

A contact investigation is 

required for all confirmed 

cases that have infectious 

forms of TB disease (e.g., 

TB disease of the lungs, 

airways, or larynx). 

If it is later determined that 

the suspect case does not 

have infectious TB disease, 

the contact investigation 

should be stopped. 

The contact investigation 

process should be started 

for persons suspected 

of having infectious TB 

disease, even before 

confirmation.
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Module 8—Contact Investigations for Tuberculosis 

Cases with Noninfectious Forms of TB Disease

Cases with noninfectious forms of TB disease generally do not 

require a contact investigation. This includes cases that only 

have extrapulmonary TB disease (e.g., TB disease in the brain, 

the kidneys, or the bones and joint). 

Cases Younger than 10 Years of Age

In most instances, a contact investigation is not necessary for 

children younger than 10 years of age. This is because they 

are less likely to transmit M. tuberculosis. If the case is 

younger than 5 years of age, a source case investigation

might be indicated (for more information, see the Source Case 

Investigations section of this module, page 76).

For more specific information on initiating a contact 

investigation, refer to the CDC Guidelines for the Investigation 

of Contacts of Persons with Infectious Tuberculosis, available 

from the CDC website (www.cdc.gov/tb).

When Should the TB Contact Investigation Begin?

In all U.S. jurisdictions, clinicians are required to rapidly report 

TB disease or a suspicion of TB disease to public health 

authorities. The first few steps of the TB contact investigation 

process should start as soon as a suspected or confirmed 

infectious TB case comes to public health attention. This 

includes reviewing medical information and interviewing the 

case within one working day after the case is reported to the 

health department. 

It is important to respond promptly because

 Some contacts may already have TB disease and are in 

need of treatment;

 Some contacts could be at risk for rapid development of 

TB disease;

 Some contacts may become more difficult to locate as time 

goes by, such as homeless persons;

 There could be ongoing transmission of M. tuberculosis; and

 Cases may have difficulty remembering all of their contacts 

as time goes by.

Contact investigations initiated for suspect TB cases 

should be stopped if it is later determined that the person 

does not have infectious TB disease.

Cases with noninfectious 

forms of TB disease 

generally do not require 

a contact investigation.

In most instances, a 

contact investigation 

is not necessary for 

children younger than 

10 years of age.

The first few steps of the 

TB contact investigation 

process should start as 

soon as a suspected or 

confirmed infectious TB 

case comes to public 

health attention.
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Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.1–8

8.1 What is a TB contact investigation?

 8.2 What are the goals of a TB contact investigation?

8.3 Which TB cases require a contact investigation?

8.4 Who is responsible for conducting TB contact investigations?

Answers to study questions are on pages 83– 89
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Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

You are a TB case manager at a busy clinic. Two new TB cases have been assigned to you. Indicate 

which case(s) require a contact investigation and note the reason why you made your decision.

 Jose is a 35-year-old agricultural worker diagnosed with extrapulmonary TB of the 

kidneys. He lives with his wife in a small, rented house in a rural area. 

 Dale is a 72-year-old widower who lives alone. He drives himself to the local 

retirement center for bingo and poker four times a week. He was recently evaluated 

for TB disease by his physician because he complained of having a cough, shortness 

of breath, fatigue, and weight loss. His sputum smears were positive and his culture 

results are pending. Dale’s chest x-ray shows a cavity in the right upper lobe of his 

lungs. The physician suspects TB and started Dale on a four-drug regimen. 

Answers to case studies are on pages 90– 98
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Module 8—Contact Investigations for Tuberculosis 

How Should TB Contact Investigations be 

Prioritized?

Because of limited resources and competing demands, 

health departments may not be able to complete the contact 

investigation process for all confirmed or suspected infectious 

TB cases promptly. Thus, health departments may need to 

prioritize among contact investigations and dedicate resources 

to those considered a higher priority. 

If a health department needs to prioritize between contact 

investigations, the focus should be on contact investigations 

where the likelihood of transmission is high and contacts are at 

an increased risk for rapid development of TB disease. 

In general, priority should be given to contact investigations 

involving

 Cases that are likely to be highly infectious 

 Settings where transmission of M. tuberculosis is likely 

 Contacts at high risk for rapid development of TB disease if 

infected with M. tuberculosis

Highly Infectious Cases

Transmission of M. tuberculosis depends on a variety of factors, 

but it is more likely to occur when a case is highly infectious. 

Highly infectious cases generally have one or more of the 

following characteristics: 

 Pulmonary, laryngeal, or pleural TB

 Positive sputum smear results

 Cavities on chest x-ray

 Actions that can increase the likelihood of transmission

 Coughing

 Sneezing

 Singing

For example, a case with pulmonary TB who was coughing for 

three months before receiving treatment and who has positive 

sputum smears is more likely to be infectious than a case who 

has negative sputum smears and has rarely been coughing. 

Therefore, the first case would be considered a higher priority 

for a contact investigation. 

If a health department 

needs to prioritize between 

contact investigations, the 

focus should be on contact 

investigations where the 

likelihood of transmission 

is high and contacts are at 

an increased risk for rapid 

development of TB disease. 

Transmission of 

M. tuberculosis depends 

on a variety of factors, but it 

is more likely to occur when 

a case is highly infectious.
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Module 8—Contact Investigations for Tuberculosis 

Settings Where Transmission of M. tuberculosis is Likely

Another factor to consider when prioritizing among contact 

investigations is the setting in which transmission may have 

occurred. Transmission is more likely if there is a high 

concentration of M. tuberculosis in the air. The concentration of 

bacteria in the air is affected by the setting’s

 Size

 Ventilation 

 Air-cleaning system 

M. tuberculosis is more likely to be transmitted in small, 

crowded spaces that do not have adequate airflow. For example, 

transmission is more likely in a small office with little or no 

ventilation than it is in a large, well-ventilated grocery store. 

Settings with air-cleaning systems such as high-efficiency 

particulate air (HEPA) filters and ultraviolet lights can decrease 

the concentration of M. tuberculosis in the air. (For more 

information, refer to Module 5, Infectiousness and Infection 

Control.)

In addition to the size, ventilation, and air-cleaning systems 

of the setting, it is also important to consider activities that 

have occurred in the setting that can increase the likelihood 

of transmission. For example, medical procedures such as 

bronchoscopy, sputum induction, TB wound irrigation, or 

autopsy of TB cases can produce a high concentration of 

M. tuberculosis in the air. Therefore, contact investigations 

involving settings where these procedures take place should be 

considered a priority.

Contacts at High Risk for Rapid Development of TB 

Disease if Infected with M. tuberculosis

Contacts who are at a particularly high risk for rapidly 

developing TB disease after infection with M. tuberculosis

include 

 Children younger than 5 years of age 

 Persons with weakened immune systems due to

 HIV infection

 Immunosuppressive therapy, including TNFalpha antagonists, prolonged use of high-dose 

adrenocorticosteroids, or medications received after organ 

transplantation 

Any contact investigation involving these persons should be 

given priority. 

Transmission is more 

likely if there is a high 

concentration of 

M. tuberculosis in the air.
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Module 8—Contact Investigations for Tuberculosis 

Who Conducts the TB Contact Investigation?

A TB contact investigation involves many different steps and 

procedures. Depending on the program, the activities of the 

contact investigation may be conducted by an individual or a 

contact investigation team.

The staff involved in conducting a contact investigation can 

include

 Case managers

 Field investigators

 Outreach workers

 Epidemiologists and surveillance staff

 Program managers

The actual job titles for team members may vary by jurisdiction. 

In some jurisdictions, one staff member may fill several roles. 

Ideally, one person should be assigned responsibility for the 

overall management of the investigation to ensure all activities 

of the contact investigation are conducted. In certain situations, 

infection control professionals or other staff from facilities 

where exposure occurred may be involved as part of the contact 

investigation team.

For the purposes of this module, the person responsible for 

conducting the contact investigation will be referred to as the 

“contact investigator.”

What Knowledge and Skills are Necessary to 

Conduct a TB Contact Investigation?

To conduct a TB contact investigation, it is ideal for the contact 

investigator and others on the team to have the following 

knowledge and skills:

 A basic understanding of TB transmission and pathogenesis 

(for more information, refer to Module 1, Transmission and 

Pathogenesis of Tuberculosis)

 Effective communication skills to build trust and rapport 

with the case during interviews (for more information, refer 

to page 29 of this module)

 Data management and data analysis skills

 An understanding of TB genotyping

Ideally, one person 

should be assigned 

responsibility for the 

overall management 

of the investigation to 

ensure all activities of 

the contact investigation 

are conducted.
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Module 8—Contact Investigations for Tuberculosis 

Data Management and Data Analysis

To successfully conduct a contact investigation, investigators 

need to have skills in data management and data analysis. 

This is because contact investigations typically involve a 

large amount of demographic, medical, and epidemiologic 

information that needs to be systematically collected, organized, 

and analyzed. This data is typically used for case management, 

epidemiologic analysis, and program evaluation. 

When conducting a contact investigation, public health 

programs need to determine

 Which data needs to be collected and why 

 Who is responsible for collecting and how

 How data is to be managed and safeguarded

Data management during a TB contact investigation can be very 

time consuming. Therefore, the benefits of having the data must 

justify the level of effort and resources required. 

An Understanding of TB Genotyping

TB genotyping is a laboratory-based method that can 

determine the genetic pattern of the strain of M. tuberculosis

that caused TB disease in a person. Each strain has a distinct 

genetic pattern, or genotype. Genotyping is done for culturepositive cases of TB disease.

In the United States, genotyping information on individual 

cases is available to state and local health departments through 

the TB Genotyping Information Management System 

(TB GIMS), a secure CDC-sponsored online national database 

of genotyping and case information. 

Typically, genotype information will not be available during 

the early stages of a contact investigation. When it does 

become available, the results can help confirm, disprove, or 

detect connections among cases. If two cases have matching 

genotypes, they may be connected even if the connection is not 

recent or obvious. For example, two persons whose TB strains 

match by genotype might not know one another, but they may 

have both been exposed to the same infectious case several 

years earlier. (For more information on genotyping, refer to

Module 9, Tuberculosis Outbreak Detection and Response.)

Contact investigations 

typically involve a large 

amount of demographic, 

medical, and epidemiologic 

information that needs to 

be systematically collected, 

organized, and analyzed.

Typically, genotype 

information will not be 

available during the 

early stages of a contact 

investigation. When it 

does become available, 

the results can help 

confirm, disprove, or detect 

connections among cases.
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Module 8—Contact Investigations for Tuberculosis 

Study Question 8.

8.5 Which TB contact investigations should be given priority? 

Answers to study questions are on pages 83– 89
Module 8—Contact Investigations for Tuberculosis 

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Systematic Approach to TB 

Contact Investigations

How is a TB Contact Investigation Conducted?

Contact investigations should be conducted using a systematic 

process that includes the following 10 steps: 

1. Review existing information about the case

2. Determine an initial estimate for the infectious period and 

estimate the degree of infectiousness

3. Interview the case

4. Review information and develop a plan for the 

investigation 

5. Refine the infectious period and degree of infectiousness 

6. Prioritize contacts

7. Conduct field visits 

8. Conduct contact assessments

9. Determine whether to expand or conclude an investigation

10. Evaluate the contact investigation activities 

The actual sequence and timing of contact investigation steps 

and activities may vary from one investigation to another. 

Moreover, local public health programs may have additional 

guidance on policies and procedures for conducting contact 

investigations within their jurisdictions. These policies and 

procedures should be written and available to staff responsible 

for conducting contact investigations. Regardless of variations 

among local program policies, an effective investigation will 

include all of the above 10 steps. This section of the module 

will provide an overview of each of the steps. 

The actual sequence 

and timing of contact 

investigation steps 

and activities may vary 

from one investigation 

to another.
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Module 8—Contact Investigations for Tuberculosis 

Step 1. Review Existing Information about the Case

As soon as a suspected or confirmed case of TB comes to public 

health attention, contact investigators should begin gathering 

and reviewing all existing information about the case. 

Existing information can help the investigator

 Estimate the infectious period 

 Estimate the degree of infectiousness 

 Identify potential contacts

 Identify potential exposure locations

 Conduct effective interviews

Reviewing the existing information is sometimes referred to as 

the pre-interview phase. 

Information to Collect and Review before the Initial 

Interview with the Case

The following information should be collected and reviewed 

during the pre-interview phase:

Medical Information

 Site(s) of TB disease

 Current TB treatment regimen 

 TB symptoms and estimated onset date 

 Chest x-rays or other diagnostic imaging dates and results 

 Tuberculin skin test (TST) or interferon-gamma release 

assay (IGRA) dates and results 

 Sputum smear and culture dates and results

 Nucleic acid amplification (NAA) test dates and results

 Genotype results (if available)

 HIV test dates and results

 Details about prior diagnosis with LTBI or TB disease, and 

any treatment 

 Medical risk factors that could have increased the case’s 

risk for infection with M. tuberculosis or development of 

TB disease

Demographic and Social Information

 Name and aliases

 Date of birth

 Gender

 Addresses and telephone numbers

 Preferred language

As soon as a suspected or 

confirmed case of TB comes 

to public health attention, 

contact investigators 

should begin gathering 

and reviewing all existing 

information about the case. 
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Module 8—Contact Investigations for Tuberculosis 

 Next of kin, emergency contacts, and names of parents or 

guardians, if the case is a minor

 Details about any known TB exposures

 History of substance use, mental illness, or any other issues 

that could affect the interview or the contact investigation

 Social or behavioral risk factors that could have increased 

the case’s risk for infection with M. tuberculosis or 

development of TB disease

 Contact names, particularly children or persons with 

weakened immune systems, who live with or frequently 

spend time with the case

 Recent travel or immigration

 History of jail or homelessness

Some of the above information may not be available during 

the pre-interview phase. If information cannot be obtained at 

this step, the investigator should obtain it during the interview 

phase. 

Sources of Information for TB Cases

Pre-interview information can be obtained from the following 

sources:

 Public health records

 Medical records

 Discussions with the case’s clinicians

 Tuberculosis Genotyping Information Management System 

(TB GIMS)

Public Health Records 

Contact investigators should cross-check locally available 

TB registries and surveillance databases to determine if the 

case was previously included in a TB contact investigation 

or diagnosed with LTBI or TB disease. Information from the 

Report of Verified Case of Tuberculosis (RVCT) should also be 

reviewed. 

Additional information about the case’s HIV status and any 

prior TB exposure, assessment, or treatment may also be found 

by reviewing health department’s HIV and STD surveillance 

records. 

Medical Records 

All available and relevant medical records for the case, 

including any from the health department, hospital, clinic, and if 

applicable, long-term care facility or correctional facility, should 

be reviewed. 
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Module 8—Contact Investigations for Tuberculosis 

For cases who were hospitalized while infectious, nurse 

progress notes may include the names of family and friends 

who visited. In addition, health insurance information may 

provide the work location of the case. This information can help 

identify potential contacts and can be used as prompts during 

case interviews. 

Discussions with the Case’s Clinicians

Speaking with the case’s private or public clinicians can help 

clarify information obtained from medical records as well as 

provide additional details about the case. 

Tuberculosis Genotyping Information Management System 

(TB GIMS)

Typically, genotype information will not be available during the 

early stages of a contact investigation. Genotyping information 

for specific cases is available to state and local health 

departments through TB GIMS. Local health departments can 

access genotyping data in various ways, usually either through 

TB GIMS directly or from the state TB program.

For more information about TB GIMS, please refer to the CDC 

website on TB GIMS (www.cdc.gov/tb/publications/factsheets/

statistics/gims.htm).

Step 2: Determine an Initial Estimate for the 

Infectious Period and Estimate the Degree of 

Infectiousness 

The infectious period is the time during which a case is 

potentially capable of transmitting M. tuberculosis. As there is 

no well-established method to determine the exact start date 

of the infectious period, it must be estimated. Estimating a 

case’s infectious period helps to focus investigation efforts on 

identifying contacts who were most likely exposed to 

M. tuberculosis while the case was infectious.

Contact investigators should prepare an initial estimate for the 

infectious period based on information collected during the 

pre-interview phase. This initial estimate will be revised as 

additional information becomes available throughout the contact 

investigation process. 

Below is a method to help estimate the infectious period. For 

more specific information on estimating the infectious period, 

refer to the CDC Guidelines for the Investigation of Contacts of 

Persons with Infectious Tuberculosis, available from the CDC 

website (www.cdc.gov/tb).

Estimating a case’s 

infectious period helps to 

focus investigation efforts 

on identifying contacts who 

were most likely exposed 

to M. tuberculosis while 

the case was infectious. 

The infectious period is 

the time during which 

a case is potentially 

capable of transmitting 

M. tuberculosis.
19

Module 8—Contact Investigations for Tuberculosis 

Estimating the Start of the Infectious Period for Sputum 

Smear Positive Cases

For cases that have positive sputum smears, the minimum start 

date of the infectious period is usually 3 months before the onset 

of respiratory symptoms (e.g., cough) or 3 months before the 

first finding consistent with TB disease, whichever is earlier. 

For example, if the case’s symptoms started on November 1st, 

the start of the infectious period would be August 1st (3 months 

before the symptoms started). See Figure 8.1. 

Some cases may not remember when their TB symptoms began, 

and others may report that they have had no symptoms. In 

this situation, the start of the infectious period should be, at a 

minimum, 3 months before the first finding consistent with TB 

disease. For example, if a case has had no symptoms, but had a 

chest x-ray taken on September 1st which showed a cavity, the 

start of the infectious period would be June 1st (3 months before 

the chest x-ray).

Estimating the Start of the Infectious Period for Sputum 

Smear Negative Cases

For TB cases with TB symptoms and negative sputum smear 

results, the start of the infectious period would be 3 months 

before symptom onset or 3 months before the first finding 

consistent with TB disease, whichever is earlier. 

For TB cases with negative sputum smear results, no symptoms, 

and no pulmonary cavities, the start of the infectious period is 

1 month (4 weeks) before TB disease was first suspected by a 

healthcare provider. For example, if the healthcare provider first 

suspected TB disease on September 15th, the infectious period 

would be 1 month before that date (August 15th). See Figure 8.2.

Table 8.1 shows recommendations for estimating the start of the 

infectious period. 

For cases that have positive 

sputum smears, the 

minimum start date of the 

infectious period is usually 

3 months before the onset 

of respiratory symptoms 

(e.g., cough) or 3 months 

before the first finding 

consistent with TB disease, 

whichever is earlier. 
20

Module 8—Contact Investigations for Tuberculosis 

Table 8.1—Recommendations for Estimating the Start of the Infectious Period by Case Characteristics

Case with 

Respiratory TB 

Symptoms

Case with 

Positive

Sputum Smear 

Case with 

Pulmonary 

Cavity on 

Chest X-ray

Recommended Minimum Beginning of the 

Infectious Period

Yes No No 3 months before symptom onset or first finding 

consistent with TB disease, whichever is longer

Yes Yes Yes 3 months before symptom onset or first finding 

consistent with TB disease, whichever is longer

No No No 1 month (4 weeks) before date of suspected diagnosis

No Yes Yes 3 months before finding consistent with TB disease

Estimating the End of the Infectious Period

The infectious period ends when all of the following are met: 

 Effective treatment 2 weeks or longer;

 Diminished symptoms (e.g., coughing less); and 

 Mycobacteriologic response (e.g., decrease in grade of 

sputum smear positivity).

If a case is returning to a congregate setting, or to any other 

setting where susceptible persons may be exposed, he or she 

should have at least three consecutive negative sputum smear 

results before being considered noninfectious.

For contact investigation purposes, the infectious period can 

also end when the case is isolated under airborne infection 

isolation precautions, even if not all of the criteria above have 

been met. This is because these precautions limit the case’s 

ability to transmit M. tuberculosis to additional contacts. 

Figure 8.1 shows an example of how to determine an initial 

estimate for the beginning and end of the infectious period for 

a case with a positive sputum smear result and symptoms of TB 

disease. In this example, the case had negative sputum smears, 

no symptoms, and over 2 weeks of treatment by December 1st. 

Therefore, the end of the infectious period would be December 1st.
21

Module 8—Contact Investigations for Tuberculosis 

Figure 8.1—Example of determining an initial estimate of the infectious period for a smear positive case 

with TB symptoms. 

Figure 8.2—Example of determining an initial estimate of the infectious period for a smear negative case 

who does not have TB symptoms or a cavity on chest x-ray. 

3 months before symptom onset; 

start of infectious period

Symptom 

onset

The infectious period starts 3 months before symptom onset 

and ends the date that the case meets all of the criteria for 

ending the infectious period (August 1st to December 1st) 

Effective treatment for 

2 weeks or longer; 

diminished symptoms; and 

mycobacteriologic response; 

end of infectious period

Treatment 

started 

Nov. 15th

June

1

July

1

August

1

September

1

October

1

November

1

December

1

Infectious Period Estimate for a Smear Positive Case with TB Symptoms 

The infectious period starts 1 month (4 weeks) before the date TB was first suspected 

by a healthcare provider and, for contact investigation purposes, ends the date that 

the case was appropriately isolated (August 15th to September 15th) 

August

1

August

15

September

1

September

15

October

1

October

15

Infectious Period Estimate for a Smear Negative Case 

without TB Symptoms and No Cavities on Chest X-Ray

1 month before the healthcare 

provider first suspected TB; 

start of infectious period

• Healthcare provider first suspects TB

• Case isolated in healthcare facility for treatment 

of TB disease; end of infectious period
22

Module 8—Contact Investigations for Tuberculosis 

Estimating the degree of 

infectiousness of a case 

helps investigators focus 

contact investigation 

efforts. The greater the 

degree of infectiousness, 

the more likely that 

transmission occurred. 

Figure 8.2 shows an example of how to determine an initial 

estimate of the beginning and end of the infectious period 

for a case with a negative sputum smear result, no pulmonary 

cavities, and no symptoms of TB. In this example, the case was 

isolated on September 15th, the same date that TB was first 

suspected. Therefore, the end of the infectious period would be 

September 15th.

Estimating the Degree of Infectiousness

Estimating the degree of infectiousness of a case helps 

investigators focus contact investigation efforts. The greater 

the degree of infectiousness, the more likely that transmission 

occurred. 

An initial estimate for the degree of infectiousness can be made 

during the pre-interview phase. If an estimate is made, it may 

need to be revised after the interview with the case and as the 

investigation continues. 

Table 8.2 presents factors that should be taken into 

consideration when determining the degree of infectiousness of 

a case.

Table 8.2—Factors Associated with Infectiousness and Noninfectiousness 

Factors Associated with More Infectiousness Factors Associated with Less Infectiousness

Presence of a cough No cough 

Cavity in the lung No cavity in the lung 

Acid-fast bacilli on sputum smear No acid-fast bacilli on sputum smear 

TB of the lungs, airway, or larynx Most extrapulmonary (non-respiratory) TB 

Patient not covering mouth or nose when coughing Patient covering mouth or nose when coughing

Not receiving adequate treatment or having 

prolonged illness Receiving adequate treatment for 2 weeks or longer 

Undergoing cough-inducing procedures Not undergoing cough-inducing procedures 

Positive sputum cultures Negative sputum cultures

For more information on infectiousness, see Module 5, Infectiousness and Infection Control. 
23

Module 8—Contact Investigations for Tuberculosis 

Study Question 8.6–8

8.6 What is the infectious period?

8.7 When does the infectious period end?

Answers to study questions are on pages 83– 89
24

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

Calculate the infectious periods for the following TB cases:

 Isaac is a 42-year-old man who was hospitalized on December 4th with symptoms 

of fever, night sweats, and cough. He was placed in airborne infection isolation. On 

the same date (December 4th), AFB sputum smears were collected and reported as 

positive with final cultures pending. Chest x-rays were taken on December 4th and 

reported as abnormal with cavitary disease. 

Isaac was diagnosed with suspected pulmonary TB and appropriate TB treatment was 

started on December 5th. Isaac states that he started coughing around November 

6th. His symptoms resolved on December 24th. Three consecutive sputum AFB smears 

were negative on February 10th.

 Trang is a 52-year-old woman who had a checkup with her primary care provider on 

May 19th. During this visit, she was found to have an abnormal chest x-ray. Sputum 

collected on the same day was reported as AFB smear positive with final cultures 

pending. On May 20th she was diagnosed with suspected pulmonary TB, started 

appropriate treatment, and was put on home isolation. Trang claims she never had a 

cough or any other symptoms. Three consecutive induced sputum AFB smears were 

negative on June 15th, June 18th, and June 21st. 

Answers to case studies are on pages 90– 98
25

Module 8—Contact Investigations for Tuberculosis 

Step 3: Interview the Case

The foundation of an effective contact investigation is the case 

interview. If the investigator does not communicate well with 

the case to obtain accurate information, persons who need 

medical assessment and treatment may be missed. To obtain 

complete and accurate information from the case, it is important 

that the contact investigator is trained and skilled in conducting 

interviews.

What is the Main Goal of the Case Interview?

The main goal of the case interview is to identify contacts 

who may have been exposed to M. tuberculosis. To gather 

information about contacts, the investigator should ask the case 

 Where he or she spent time during infectious period

 What activities or events he or she participated in during 

infectious period

 Whom he or she spent time with during infectious period

Where the Case Spent Time During Infectious Period 

Asking the case about places where he or she spent time can 

help determine whom he or she spent time with during the 

infectious period. These places can include locations of

 Residence

 Work, school, or volunteer activities

 Social, leisure, religious, or recreation activities

 Illicit or illegal activities

For each place identified, the case should be asked about the

 Amount of time spent in each place

 Characteristics of each place, such as room size, crowding, 

and whether windows were open or closed

This information can help the investigator estimate the risk of 

transmission for each place and, thus, prioritize field visits for 

assessing the various sites. 

Compiling a list of places is also useful because the case may 

not always be able to provide enough information about each 

of his or her contacts. This information about places could then 

be used to conduct a location-based investigation. For more 

information about conducting a location-based investigation, 

refer to page 45 of this module. 

The foundation of 

an effective contact 

investigation is the case 

interview. If the investigator 

does not communicate 

well with the case to obtain 

accurate information, 

persons who need 

medical assessment and 

treatment may be missed.

The main goal of the 

case interview is to 

identify contacts who 

may have been exposed 

to M. tuberculosis.

Asking the case about 

places where he or she 

spent time can help 

determine whom he or 

she spent time with during 

the infectious period.
26

Module 8—Contact Investigations for Tuberculosis 

What Activities and Social Events the Case Participated in 

During Infectious Period 

In addition to asking the case about places where he or she has 

spent time, the investigator should ask about activities during 

the infectious period. It can be helpful for the case to outline a 

typical day starting with getting up in the morning until going to 

bed at night. Asking specifically about participation in activities 

or special events such as parties or holiday celebrations might 

help the case remember additional exposure settings and 

contacts. Reviewing a calendar or appointment book with the 

case could also be helpful for determining travel, holidays, and 

social events during the infectious period.

The investigator should also specifically ask the case if he or she 

was involved in any activities such as volunteering in a nursing 

home, day care, or hospital, where persons who are at high risk 

for rapid development of TB disease could have been exposed.

Whom the Case Spent Time with During Infectious Period

The investigator should ask the case to give the names and 

aliases of persons with whom he or she spent time while 

infectious. This includes any persons who live in the same 

home or share a sleeping space with the case. Additionally, the 

investigator should identify any persons with whom the case 

spent a lot of time. The compiled list of places and activities 

should be used to prompt the case to remember persons with 

whom he or she spent time.

The case should be asked specifically about any time spent with 

contacts who

 Have symptoms of TB disease, such as cough or weight loss;

 Are younger than 5 years of age;

 Have a medical condition that weakens the immune system 

(e.g., HIV or immunosuppressive therapy).

Another strategy to identify contacts is to review the case’s cell 

phone directory and online social networking accounts (e.g., 

Facebook, LinkedIn). This can help the case remember friends 

and events. This should be done with the case’s permission. 

For each contact listed, the investigator should obtain locating 

information, phone number(s), or preferably both so that he or 

she can be notified about their exposure to TB. 

The investigator should ask 

the case about activities 

during the infectious 

period. It can be helpful 

for the case to outline a 

typical day starting with 

getting up in the morning 

until going to bed at night.

The investigator should ask 

the case to give the names 

and aliases of persons 

with whom he or she spent 

time while infectious.
27

Module 8—Contact Investigations for Tuberculosis 

If the case does not have enough information to help identify 

or find some contacts, the investigator should ask him or her 

for ideas on how to gather the information from other sources 

(e.g., a work roster).

Investigators should be aware that the case may be reluctant 

to talk about some or all of their contacts. For example, a case 

may not want to identify people who use illegal drugs, reside 

in the United States illegally, or he or she may be worried 

about confidentiality. The interviewer should be sensitive to 

the case’s fears, explain the importance of testing contacts, and 

assure the case that all information will be kept confidential.

What Are Additional Objectives of the Case Interview?

Additional objectives of the case interview are to 

 Discuss the contact investigation process;

 Educate about TB disease; and 

 Confirm and expand upon information obtained from the 

pre-interview phase. 

Discuss the Contact Investigation Process

When interviewing a case, the investigator should go over 

the process and the reasons for the interview. A case who 

understands why and how a contact investigation happens 

is more likely to provide information to help find his or 

her contacts. The investigator should ensure that the case 

understands that all information provided will remain 

confidential to the extent possible and that information will be 

shared with only persons who need to know (e.g., other public 

health personnel). The case should be informed that sometimes 

despite best efforts their TB status may be inadvertently 

disclosed to others. For example, the case’s friend, family 

member, or co-worker may share information to others. The 

case and the investigator should discuss this possibility and be 

prepared to address the situation if privacy is not maintained. 

To prevent breaches in confidentiality, the case should be 

advised to inform only persons he or she trusts about their TB 

diagnosis. (For more information on confidentiality, see Module 

7, Patient Rights and Confidentiality in Tuberculosis Control.)

Educate about TB Disease

During the interview, it is important to assess the case’s 

knowledge about TB. The case may have little to no 

knowledge or have misconceptions about TB. The case 

interview can be an opportunity to educate the case about 

TB transmission and treatment. A case who understands his 

Additional objectives of 

the case interview are 

to discuss the contact 

investigation process, 

educate the case about 

TB disease, and confirm 

and expand upon 

information obtained from 

the pre-interview phase.

A case who understands 

why and how a contact 

investigation happens 

is more likely to provide 

information to help 

find their contacts.
28

Module 8—Contact Investigations for Tuberculosis 

or her TB diagnosis and how TB is transmitted is more likely 

to be invested in the contact investigation, as well as their TB 

treatment. Patient education materials may be useful to bring 

to the interview. (For more information on patient education 

strategies, refer to Module 6, Managing Tuberculosis Patients 

and Promoting Adherence.)

Confirm and Expand Upon Information Obtained from 

the Pre-Interview Phase

The case interview is also an opportunity to confirm and 

expand upon information collected during the pre-interview 

phase. The case may be able to provide additional information 

and details that were not captured by the medical record review.

The investigator should specifically ask about any TB symptoms 

and TB history, as well as confirm personal and medical 

information. Any additional information about the onset of 

symptoms can be used to refine the estimated infectious period. 

When and Where Should the Case Interview be 

Conducted?

The initial interview should be within one working day after 

an infectious case is reported to the health department. This 

allows the investigator to find contacts who may already have 

TB disease as soon as possible.

A re-interview should be scheduled for 1–2 weeks after the 

initial interview so that the case will have had time to adjust to 

their TB diagnosis and treatment. The re-interview is also an 

opportunity to continue to build a trusting relationship between 

the case and the investigator and to learn about more contacts.

Additional interviews should be scheduled as needed. Reinterviews do not need to be formal. Investigators can continue 

to collect information throughout the process. For example, 

some re-interviews can be conducted during directly observed 

therapy (DOT) visits or field visits. 

The interviews should be done in person (see Figure 8.3). The 

interviews can be in the hospital, the TB clinic, the case’s home, 

or any other location that is convenient for the case and that 

respects his or her privacy. Health care workers should follow 

infection control precautions while interviewing someone who 

has potentially infectious TB. 

The case interview 

can be an opportunity 

to educate the case 

about TB transmission 

and treatment.

The initial interview should 

be within one working 

day after an infectious 

case is reported to the 

health department.

Interviews can be in the 

hospital, the TB clinic, the 

case’s home, or any other 

location that is convenient 

for the case and that 

respects his or her privacy. 
29

Module 8—Contact Investigations for Tuberculosis 

Figure 8.3—Contact investigator interviewing a case who is no longer considered infectious.

What are Some Strategies for Conducting 

Effective Interviews?

Some strategies for effective interviews are summarized in 

Table 8.3. Additionally, several training resources are available 

for enhancing interviewing skills, including Effective TB 

Interviewing for Contact Investigation: Self-Study Modules 

and the Effective TB Interviewing for Contact Investigations 

DVD, both available from the CDC website (www.cdc.gov/tb/

education).

Building Trust and Rapport

The most important skill in conducting an interview is the 

ability to build trust and rapport with the case. This can help 

ensure that the case is comfortable in providing information that 

is important to the contact investigation. For example, a case 

may feel stigma associated with TB disease and may be reluctant 

to share the names of his or her contacts. Additionally, a case 

may be involved in illegal activities and not feel comfortable 

The most important skill in 

conducting an interview 

is the ability to build trust 

and rapport with the case.
30

Module 8—Contact Investigations for Tuberculosis 

sharing information about those activities and contacts with the 

investigator. Thus, it is important that the contact investigator 

builds a trusting relationship with the case by finding common 

ground, using effective communication skills, maintaining 

confidentiality, and displaying respect and empathy. Finding 

common ground typically does not have to do with the case 

having TB disease. For example, the investigator and the case 

may find that they have similar hobbies and interests. (Refer 

to Module 6, Managing Tuberculosis Patients and Promoting 

Adherence, for more information regarding trust and rapport.)

Using Open-Ended Questions

During the interview, contact investigators should use openended questions to gather information from the case. Openended questions encourage discussion because they encourage 

more than a “yes” or “no” response. The questions in Table 8.4 

are examples of open-ended questions that can be used during 

interviews. 

Using an Interview Checklist

To ensure that interview objectives are being met, an interview 

checklist can be used. The use of an interview checklist can 

prompt the investigator to obtain information on places and 

activities, as well as remind the investigator to educate the 

case about TB and the contact investigation process. Although 

the use of a checklist can help ensure that all of the interview 

objectives are systematically met, it is important to remember 

that the interview is a conversation between the interviewer 

and the case. The interviewer should be flexible and allow 

for a natural flow of the conversation. The interview checklist 

should not be a distraction while trying to build rapport with 

the case. Furthermore, the investigator should be alert to other 

information that may not be reflected on the checklist. Figure 

8.4 shows an example of a checklist that can be used during a 

case interview.

Depending on the situation, other tools may be helpful during 

an interview. For example, some jurisdictions that encounter 

cases among homeless populations may have a list of temporary 

shelters that can be used to help prompt the investigator to ask 

the case about each location.

During the interview, 

contact investigators 

should use open-ended 

questions to gather 

information from the case.

Although the use of 

a checklist can help 

ensure that all of the 

interview objectives are 

systematically met, it is 

important to remember 

that the interview is a 

conversation between the 

interviewer and the case.
31

Module 8—Contact Investigations for Tuberculosis 

Table 8.3—Strategies for Conducting Effective TB Case Interviews 

 Have a clear understanding of the objectives of the interview.

 Plan the interview so that each objective is given adequate time.

 Ensure the interview takes place under conditions that protect the privacy of the case and encourage effective 

communication.

 Arrange for the assistance of an interpreter if you do not speak the same language as the case.

 Establish the foundation for an effective working relationship based on trust and respect. 

 Explain what a contact investigation is, how a contact investigation protects contacts from getting sick with TB 

disease, and what the case can do to help.

 Begin with an assessment of the case’s knowledge, feelings, and beliefs about TB.

 Remain objective, open-minded, and nonjudgmental.

 Ask open-ended questions and listen carefully to the case’s responses.

 Recognize and address the case’s fears and concerns about TB.

 Use opportunities that arise during the interview to educate the case about TB.

 What symptoms do you have?

 When did your symptoms begin?

 How long have you had these symptoms?

 When did you first go to a healthcare provider about your symptoms?

 What medications do you take for your illness?

 Where do you sleep each night?

 Who else sleeps there?

 Where else do you sleep?

 Who visits your home?

 What is your daily routine?

 How do you get to work or school?

 Who rides with you to work or school?

 What is the room like where you spend most of your time at work or school?

 Who are the persons you spend time with at work, school, church, etc.?

 Who are the persons you see every day?

 What do you do in your free time?

 Where did you go on vacation?

Table 8.4—Examples of Open-Ended Questions for TB Case Interviews 
32

Module 8—Contact Investigations for Tuberculosis 

Figure 8.4—Sample TB interview checklist. Adapted from TB Interviewing for Contact Investigation: 

A Practical Resource for the Healthcare Worker from the Global Tuberculosis Institute at Rutgers, 

the State University of New Jersey. 

TB Interview Checklist

A. Introduction

 Introduce self and provide identification

 Explain your role in TB control

 Explain the purpose of the interview

B. Information and Education Exchange

 Observe the case’s physical and mental state, body language, and communication skills

 Collect and confirm the following information:

___ Name

___ Alias/nicknames

___ Date of birth

___ Address

___ Telephone number

___ Next of kin

___ Other locating information

___ Physical description

___ Known exposure to TB

___ Recent hospitalization(s) for TB

___ Medical provider for TB

___ Transportation availability

___ Other medical conditions

___ Outpatient DOT plan

___ Barriers to adherence

 Assess disease comprehension and provide TB education

 Obtain and confirm TB symptom history

 Refine infectious period 

 Discuss case’s current diagnosis

 Discuss infection control procedures and medical appointments

C. Contact Identification

 Collect information on contacts in the household, workplace, school, congregate settings, and social or 

recreational environments during the infectious period

 Ask about any activities where they could have exposed persons at high risk for rapid development of TB 

disease (e.g., volunteering in a nursing home or day care)

 Ask the case about contacts who

{ Have symptoms of TB disease

{ Are younger than 5 years of age

{ Have a weakened immune system

 Information about contacts should include

___ Name

___ Alias/nicknames

___ Age, race, sex

___ Address

___ Telephone number

___ Other locating information

___ Physical description

___ Hours of exposure per week

___ Dates of first and last exposures

___ Location where exposure occurred

___ Frequency and duration of exposure

___ Physical proximity to case when exposure occurred

D. Conclusion of the Interview

 Request, then answer the case’s questions

 Review and reinforce the adherence plan

 Confirm next appointment (if known)

 Arrange reinterview and home visit (if not already completed)

 Leave your name and telephone number

 Thank the case and close interview
33

Module 8—Contact Investigations for Tuberculosis 

How Should Information Obtained from the Interview be 

Compiled?

During or immediately after the interview, the investigator 

should take notes to keep track of the information being 

discussed. Sometimes a contact investigation form can help 

investigators compile the information obtained from the 

interview. Ideally, investigators should complete the form after 

the interview since it may be a distraction during the interview 

and make it more difficult to develop rapport. Whatever the 

approach, key findings from the interview must be recorded in 

the public health record.

Forms used for contact investigations vary from jurisdiction to 

jurisdiction. Some jurisdictions might use a standard form but 

have additional documents that can be incorporated based on 

the situation. For example, if the contact investigation involves 

a case who is homeless, some jurisdictions may have additional 

forms that may be incorporated to record key information 

relevant to homeless shelters.

Interview Special Circumstances

Interviews Involving Minors

The age when adolescents can be interviewed without the 

presence or consent of parents or guardians is the same 

as the legal age of consent in most jurisdictions and most 

circumstances. Before interviewing minors, the investigator 

should be familiar with jurisdictional policy and legal code. 

The presence or consent from a parent or legal guardian may 

be required.

Interview Not Possible

In some instances, it is not possible to interview the case. 

The case could be deceased, difficult to locate, or medically or 

psychologically unable to participate in interviews. A contact 

investigation must still be done even if it is not possible 

to interview the case.

In these situations, information on where and with whom the 

case spent time might be obtained from

 The case’s medical records 

 Databases such as public health records and local 

correctional facility systems

 Comparison of genotypes with other cases

 Proxy interviews 

 Location-based contact investigations

During or immediately 

after the interview, the 

investigator should 

take notes to keep track 

of the information 

being discussed.

A contact investigation 

must still be done even 

if it is not possible to 

interview the case.
34

Module 8—Contact Investigations for Tuberculosis 

The case’s medical, public health, and correctional facility records 

should be carefully reviewed to see if there is any information to 

help identify contacts. The case’s TB genotype information, when 

available, should also be compared with other recent cases to 

discover potential connections to other cases. 

Additionally, proxy interviews can be used to elicit information. 

Proxy interviews are interviews conducted with persons familiar 

with the case’s practices, habits, and behaviors. Proxies may 

include family members, close friends, or other persons who 

know the case well. 

A location-based approach to contact investigations is where 

potential TB contacts are found and offered TB assessments 

onsite, if possible. This can be useful if places where the case 

spent time while infectious are known. For more information on 

location-based approach, please refer to page 45 of this module.

Proxy interviews are 

interviews conducted 

with persons familiar 

with the case’s practices, 

habits, and behaviors. 
35

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.8–8.

8.8 What is the main goal of the TB case interview? 

8.9 List three strategies for conducting effective interviews.

8.10 What is a proxy interview? Who may serve as an appropriate proxy?

Answers to study questions are on pages 83– 89
36

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

You are the public health worker assigned to conduct a contact investigation for Judith, 

a 73-year-old woman who was recently diagnosed with infectious TB disease. Judith lives 

with her daughter in a small house outside of town. You are conducting the case interview 

in her home. 

What questions should you ask Judith during the interview to learn more about 

her contacts? 

Answers to case studies are on pages 90– 98
37

Module 8—Contact Investigations for Tuberculosis 

Step 4: Review Information and Develop a Plan for 

the Investigation 

After the investigator has interviewed the case, he or she should 

meet with his or her supervisor or the contact investigation team 

to review all of the information obtained thus far and develop 

a plan on how to proceed. The planning process can be done 

during a case conference. To develop a plan, the investigator 

or team should do the following activities: 

 Refine the infectious period and degree of infectiousness for 

the case as necessary

 Prioritize contacts for assessment 

 Prioritize places to conduct field visits

All of these above activities are discussed in more detail in the 

next few steps (steps 5–7) of the systematic approach to contact 

investigation (pages 38–46 of this module).

As part of the planning process, the investigator or investigation 

team should also

 Establish a communication plan among staff and others 

involved in the investigation

 Clarify any jurisdictional issues 

 Establish timeframes and methods for investigation 

activities, data collection, and management

 Determine stakeholders

 Determine potential media interest

 Establish a schedule for case conferences or meetings to 

review challenges and progress

The investigation plan should be written and include where 

to conduct field visits, which contacts are currently considered 

a priority for assessment, and a timeline for accomplishing 

these tasks. Having a plan will help ensure that the goals and 

objectives of the contact investigation are met, and resources 

are used as efficiently and effectively as possible. Additionally, 

if the health department has multiple TB cases requiring 

contact investigations, the above information should be used to 

help prioritize which contact investigations require immediate 

attention and resources. The plan should be considered a work 

in progress with changes to be made as needed throughout the 

investigation.

After the investigator has 

interviewed the case, he 

or she should meet with 

his or her supervisor or 

the contact investigation 

team to review all of the 

information obtained 

thus far and develop a 

plan on how to proceed.

The investigation plan 

should be written and 

include where to conduct 

field visits, which contacts 

are currently considered 

a priority for assessment, 

and a timeline for 

accomplishing these tasks.
38

Module 8—Contact Investigations for Tuberculosis 

During case conferences about the contact investigation, 

investigators should note any similarities and potential 

connections to other recent TB cases in the area (e.g., 

homelessness, substance use). If cases have a characteristic in 

common, further investigation should be done to see if the cases 

are connected. This is because TB outbreaks generally involve 

persons with similar demographic characteristics and TB risk 

factors. (For more information, refer to Module 9, Tuberculosis 

Outbreak Detection and Response.) 

Step 5: Refine the Infectious Period and Degree of 

Infectiousness 

At the planning meeting, the investigator should use the 

information from the initial interview to determine if 

the estimates of the infectious period and the degree of 

infectiousness need to be refined. 

For example, the initial estimate of the infectious period for 

the case described in Figure 8.1 (page 21) was August 1st 

to December 1st, based on information collected in the preinterview phase. If the interview revealed that the case’s 

symptoms actually started September 1st, instead of November 

1st, the infectious period would need to be revised. Rather than 

beginning on August 1st, the infectious period should begin on 

June 1st (3 months before symptoms began). Figure 8.5 shows 

the refined infectious period for the case presented in Figure 8.1.

Additionally, from the initial interview it may become known 

that the case participated in certain activities that may influence 

the degree of infectiousness. For example, during the interview 

the investigator may find out that the case sang in a choir during 

their infectious period. Since singing is considered an action 

that increases infectiousness, the initial estimate for the degree 

of infectiousness would need to be refined. The increased 

degree of infectiousness estimate will have implications for 

the prioritization of the contact investigation, as well as for the 

prioritization of contacts needing assessment.

At the planning meeting, 

the investigator should 

use the information from 

the initial interview to 

determine if the estimates 

of the infectious period and 

the degree of infectiousness 

need to be refined. 
39

Module 8—Contact Investigations for Tuberculosis 

Figure 8.5—Example of refining the infectious period.

Step 6: Prioritize Contacts

At the planning meeting, the investigator should use information 

from the initial interview to prioritize contacts for assessment. 

The priority assigned to each contact should be based on the 

following:

 Likelihood of transmission from the case 

 Contact’s risk for development of TB disease

Some jurisdictions have tools to assist with assigning priority to 

contacts. Such tools should take both factors into account. 

The terms “close” and “casual” have been used in some public 

health programs to describe the degree of exposure contacts had 

to an infectious TB case. However, these terms do not always 

distinguish between contacts who require immediate assessment 

because of their higher risk of developing TB disease with those 

who may be at a low risk. 

The priority assigned to 

each contact should be 

based on the likelihood of 

transmission from the case 

and the contact’s risk for 

development of TB disease.

3 months before symptom onset; 

start of infectious period

Symptom 

onset

The revised estimate for the infectious period starts 3 months before 

symptom onset and ends the date that the case meets all of the 

criteria for ending the infectious period (June 1st to December 1st) 

Effective treatment for 

2 weeks or longer; 

diminished symptoms; and 

mycobacteriologic response; 

end of infectious period

Treatment 

started 

Nov. 15th

June

1

July

1

August

1

September

1

October

1

November

1

December

1

Refined Infectious Period Estimate for a Smear Positive Case with TB Symptoms
40

Module 8—Contact Investigations for Tuberculosis 

Priority should be given to locating and assessing contacts who

 Are exhibiting symptoms of TB disease

 Are at risk for rapid development of TB disease 

(e.g., contacts younger than 5 years of age and 

contacts with weakened immune systems)

 Had repeated or extended exposure to the case 

 Were exposed in an environment where transmission was 

likely, such as a small, crowded, or poorly ventilated room 

or vehicle

 Were exposed during medical procedures that can release 

substantial numbers of M. tuberculosis into the air (e.g., 

bronchoscopy)

The highest priority should be given to locating and assessing 

contacts reported by the case as having symptoms of TB disease. 

A contact with symptoms could have undiagnosed TB disease and 

be transmitting M. tuberculosis to others. 

Decisions about the priority level assigned to contacts should be 

made in consultation with supervisory clinical and management 

staff or during a case conference with the contact investigation 

team. The priority level assigned to contacts can change over 

time as new information becomes available. Thus, contacts’ 

priority assessment should be reviewed at least weekly, and 

updated as necessary based on the results of the investigation. 

For more detailed information about assigning priority to contacts, 

refer to the CDC’s Guidelines for the Investigation of Contacts 

of Persons with Infectious Tuberculosis, available from the CDC 

website (www.cdc.gov/tb).

The highest priority should 

be given to locating and 

assessing contacts reported 

by the case as having 

symptoms of TB disease. 

Decisions about the 

priority level assigned 

to contacts should be 

made in consultation 

with supervisory clinical 

and management staff or 

during a case conference 

with the contact 

investigation team. 
41

Module 8—Contact Investigations for Tuberculosis 

Study Question 8.11 – 8.

8.11 What two factors should be taken into account when determining the priority 

of each contact?

8.12 In general, which contacts should be considered priority?

Answers to study questions are on pages 83– 89
42

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

Derrick is a 47-year-old man who has had a severe cough for about two months and started 

treatment for TB disease three days ago. He lives alone in a small apartment and works the night 

shift three times a week with two other employees at the convenience store a few blocks away from 

his home. During the day, Derrick goes to friends’ apartments nearby or stays in his apartment to 

watch TV. He often goes to the local bar in his neighborhood with his friends Reggie and Melvin. He 

usually eats at one of two restaurants—the Main Street Diner or Susie’s Kitchen.

Derrick says that his girlfriend, Tonya, spends the night with him a few times a week, and often 

brings her 2 year-old son, Luke. Derrick also mentions another girlfriend, Kelly, who has stayed 

over about 10 times in the past three months. Last month, Derrick spent several days at Kelly’s 

house, where she lives with her mother.

 Based on this information, who are Derrick’s contacts?

 Which contacts are at higher risk for TB infection and TB disease?

Answers to case studies are on pages 90– 98
43

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

One week ago, Hector came to the health department complaining of night sweats, weight loss, 

and a cough that has lasted about a month. His sputum smears were positive and he started a 

four-drug regimen for TB disease.

When you interviewed Hector, you found out he lives with his 32-year-old wife, Mimi; his two 

sons, Luis, 2, and Javier, 4; and his mother-in-law, Alma, 65. Hector’s cousin, Henry, has stopped 

by the house a few times in the past month. 

Hector rides to work 5 days a week in a car with his friend Joe. The ride lasts about 30 minutes.

Hector works in a mail order packing warehouse. About 100 employees work in the main room 

with Hector, but the room is divided into several sections. There are 20 persons in Hector’s 

section, and four of these persons are assigned to work closely with Hector. Hector eats lunch 

outside every day with these four coworkers.

About twice a week and on weekends, Hector goes to a small neighborhood bar located in the 

basement of a building. At the bar, Hector spends most of the time talking to the bartender. He 

notes that the bartender has been coughing a lot lately.

 Based on this information, who are Hector’s contacts?

 Which contacts should be considered a priority?

Answers to case studies are on pages 90– 98
44

Module 8—Contact Investigations for Tuberculosis 

Step 7: Conduct Field Visits 

A field visit, also sometimes called a site visit, means visiting 

the case’s residence and other places where the case spent 

time while infectious. Field visits are an essential component 

of a TB contact investigation as they allow the investigator to 

view and assess the environment in which transmission may 

have occurred. 

In some instances, a field visit to a residence is conducted at the 

same time as the initial interview or re-interview with the case. 

Additional locations to visit can be determined by using the list 

of places reported during the interview or discussed during the 

planning meeting.

Field visits serve four main functions:

1. Identify additional cases of TB disease

2. Identify additional contacts 

3. Gather additional information about environmental 

characteristics of places where exposure occurred

4. Lay a foundation for additional contact investigation 

activities at those locations, if needed

During field visits, the contact investigator should

 Maintain confidentiality of cases and contacts 

 Refer persons with symptoms of TB disease for immediate 

medical evaluation, including a chest x-ray

 Observe environmental characteristics of the site such as 

room size, crowding, ventilation, low ceilings, and dense air

 Look for evidence of contacts not present at the time of the 

visit, such as pictures or belongings of others who may visit 

or live at the case’s residence (see Figure 8.6)

 Obtain lists of clients, employees, volunteers, and visitors 

who were present at worksites during the case’s infectious 

period 

 Explore the possibility of offering TB assessment to contacts 

onsite at that location

The field visit can also be an opportunity to educate cases and 

contacts about the purpose of a contact investigation and the 

basics of TB testing and treatment. 

The use of a standardized data collection form can assist 

investigators in recording important information about each site 

visited. Field visit forms will vary from jurisdiction to jurisdiction.

Field visits are an essential 

component of a TB contact 

investigation as they allow 

the investigator to view 

and assess the environment 

in which transmission 

may have occurred.
45

Module 8—Contact Investigations for Tuberculosis 

Figure 8.6—The investigator is conducting a field visit. She is looking for evidence of other contacts.

Location-Based Approach to Contact Investigations 

In some situations, field visits will also be used as an 

opportunity to learn about potential contacts and to offer 

onsite TB assessments for those contacts. This is referred to as 

a location-based approach to contact investigation. If a 

traditional name-based approach does not produce an adequate 

list of contacts, or if the case does not provide information 

about contacts, a location-based approach to the contact 

investigation should be considered. The goal of this approach is 

to assess persons who could have been exposed at a particular 

location (e.g., bar, drug-usage site, or shelter), but may not have 

been named as contacts. 

A location-based approach can be particularly useful when

 It is not possible to interview the case, but investigators 

can establish places where the case spent time during the 

infectious period

 A case does not or cannot provide the name or the location 

of their contacts

 Shelters or other social service agencies are unable to 

provide a list of contacts

The goal of a locationbased approach is to 

assess persons who could 

have been exposed at a 

particular location (e.g., 

bar, drug-usage site, or 

shelter), but may not have 

been named as contacts.
46

Module 8—Contact Investigations for Tuberculosis 

During location-based assessments, investigators should actively 

seek out information that could help identify priority contacts. 

Field Visit Safety

Personal Safety for the Contact Investigator

Contact investigators who conduct field visits should follow 

health department policies and local law enforcement 

recommendations regarding personal safety. Current information 

about local high-risk areas for crime can be useful in planning 

and conducting safe field visits. 

General safety precautions recommended for contact 

investigators include

 Wearing an identification badge with a current photograph

 Working in pairs when visiting isolated or dangerous areas

 Having a working cell phone

 Limiting visibility of valuable items

 Informing a coworker or supervisor of itinerary, planned 

route, and expected time of return

Infection Control Precautions

Contact investigators should follow infection control precautions 

while visiting or interviewing a potentially infectious TB case at 

any location, including the home. 

If the visit or interview takes place in an airborne infection 

isolation (AII) room, the investigator should wear an N95 

respirator for which they have been fit-tested. 

If a case is discharged home while still infectious, the 

investigator should wear an N95 respirator and the case should 

be asked to wear a surgical mask. The investigator may also 

choose to do the interview outdoors. However, because the 

sight of respirators or masks might add to the social stigma of 

TB, investigators should be careful about using them where 

others may notice. For more information about infection control 

precautions for TB, refer to Module 5, Infectiousness and 

Infection Control.

Contact investigators 

who conduct field visits 

should follow health 

department policies and 

local law enforcement 

recommendations 

regarding personal safety.

Contact investigators 

should follow infection 

control precautions while 

visiting or interviewing 

a potentially infectious 

TB case at any location, 

including the home. 
47

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.13– 8.

8.13 What are the four main functions of a field visit?

8.14 List four safety precautions investigators should take while conducting field visits.

Answers to study questions are on pages 83– 89
48

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

Carmen is a 30-year-old woman who was recently diagnosed with infectious TB disease. 

She works at the local community college and lives with her aunt.

A contact investigator from the local health department is conducting an interview with 

Carmen at Carmen’s home. Three coworkers and her aunt have been reported to be 

contacts by Carmen. 

Refer back to Figure 8.6 on page 45. Based on what is visible in the photo, is there evidence of 

any additional contacts in Carmen’s home other than her aunt? 

Answers to case studies are on pages 90– 98
49

Module 8—Contact Investigations for Tuberculosis 

Step 8: Conduct Contact Assessments 

Contact investigators should meet and assess priority contacts 

within three working days of the contact being identified. 

When meeting with the contacts, the investigator should ensure 

that confidentiality is maintained by not revealing any personally 

identifying information about the case or any specific details 

about their exposure.

The major activities of the contact assessment include

 Meeting with the contact

 Maintaining confidentiality

 Collecting and confirming information

 Conducting a medical evaluation

 Medical history

 HIV test 

 TB symptom review

 TST or IGRA to test for infection with M. tuberculosis

For more detailed information on contact assessment activities, 

refer to the Assessment and Management of TB Contacts section 

of this module, page 58. 

Step 9: Determine Whether to Expand or Conclude 

an Investigation

As part of the contact investigation process, it is important 

to continually review findings to determine if there is a need 

to expand investigation efforts beyond the priority contacts. 

Expanding the investigation includes assessing contacts who 

were not originally considered a priority or finding new contacts 

in need of TB assessment. 

Evidence of Recent Transmission

The need for expansion is generally determined by evidence 

of recent transmission. Evidence of recent transmission further 

confirms that a case was infectious and, thus, implies an 

increased likelihood that others were infected.

Evidence of recent transmission includes

 TB infection or TB disease in contacts younger than 

5 years of age

 Change in contacts’ TST or IGRA status from negative 

to positive 

Contact investigators 

should meet and assess 

priority contacts within 

three working days of the 

contact being identified.

Expanding the 

investigation includes 

assessing contacts who 

were not originally 

considered a priority or 

finding new contacts in 

need of TB assessment.

The need for expansion 

is generally determined 

by evidence of recent 

transmission.
50

Module 8—Contact Investigations for Tuberculosis 

 A greater-than-expected rate of TB disease or TB infection 

among priority contacts 

 Evidence of secondary transmission

 TB disease among contacts not initially considered priority 

(particularly if genotypes match that of the case)

TB Infection or TB Disease in Contacts Younger than 

5 years of Age

When children younger than 5 years of age have LTBI or TB 

disease, there is reason to suspect recent transmission.

Change in Contacts’ TST or IGRA Status from 

Negative to Positive 

As part of a contact assessment, contacts should receive a TST 

or IGRA to determine if they are infected with M. tuberculosis. 

Contacts with an initial negative TST or IGRA result should be 

retested 8 to 10 weeks after their last exposure to the case. If 

the result of the repeat test is positive, this implies that recent 

transmission may have occurred. (For more information on using 

TST or IGRA during contact assessments, refer to page 61.)

A Greater-than-Expected Rate of TB Disease or TB Infection 

among Priority Contacts 

Greater-than-Expected Rate of TB Disease

During a contact investigation it is not unusual to find one 

case of TB among priority contacts. An infected contact who 

develops TB disease is referred to as a secondary case of TB. 

It is important to remember that for each secondary case of 

TB, a separate contact investigation needs to be considered 

immediately.

More than one secondary case suggests the contact investigation 

may need to be expanded to other contacts. It can also mean an 

outbreak is occurring, particularly if genotypes match, because 

matching genotypes help confirm transmission links. Also, if an 

additional case in the same geographic area around the same 

time has a matching genotype, and neither case identified the 

other as a contact, contact investigators should determine if there 

were any missed connections between these two cases.

Greater-than-Expected Prevalence of TB Infection

A greater-than-expected prevalence of TB infection among 

contacts can also be evidence of recent transmission. The 

prevalence of TB infection is the percentage of persons 

infected with M. tuberculosis within a defined population. 

It is important to 

remember that for 

each secondary case of 

TB, a separate contact 

investigation needs to be 

considered immediately.

When children younger 

than 5 years of age have 

LTBI or TB disease, there 

is reason to suspect 

recent transmission.
51

Module 8—Contact Investigations for Tuberculosis 

To determine if the prevalence of infection among contacts is 

higher than expected, it is necessary to know the background 

prevalence of TB infection ideally among a local population 

similar to that of the contacts being evaluated (e.g., immigrants 

from Mexico). In the absence of information on a specific 

local population similar to the contacts being evaluated, the 

prevalence in the general population within the local area 

can be used. However, the latter prevalence will not be a 

good estimate if the contacts being evaluated are substantially 

different from the general population in terms of possible 

prior exposure to TB. If the prevalence of TB infection among 

contacts is higher than the background prevalence, this could 

indicate recent transmission and a need to expand the contact 

investigation.

The prevalence of TB infection among contacts can be 

calculated by the following steps:

1. Determine the total number of contacts who have 

completed testing (TST or IGRA). Do not include contacts 

who have a documented previous positive test result, have 

not completed testing, or who were not tested.

2. Determine the number of contacts with a newly positive 

TST or IGRA result.

3. Divide the number of contacts with a newly positive test 

result by the total number of contacts that have completed 

testing (i.e., divide the number from Step 2 by the number 

from Step 1)

4. Multiply the number from Step 3 by 100%. The resulting 

number is the TB infection prevalence for that group of 

contacts.

An example of how to determine the prevalence of newly 

diagnosed infection with M. tuberculosis among contacts is 

shown in Figure 8.7.

Evidence of Secondary Transmission

If the contact investigation for the secondary case finds 

additional persons with LTBI or TB disease, this is referred 

to as secondary transmission. Secondary transmission is 

strong evidence of a potential outbreak occurring, particularly 

if genotypes match. More information about detecting TB 

outbreaks is presented in Module 9, Tuberculosis Outbreak 

Detection and Response. 

Secondary transmission 

is strong evidence of 

a potential outbreak 

occurring, particularly 

if genotypes match.
52

Module 8—Contact Investigations for Tuberculosis 

Figure 8.7—Calculation of TB infection prevalence for a group of contacts.

Example Calculation of TB Infection Prevalence for a Group of Contacts

Eleven contacts were identified for a reported TB case. One contact had a documented previous positive TST 

result. The other 10 contacts did not have documented previous TST results. These 10 contacts had a skin test 

administered; seven had positive TST results and three had negative TST results. 

Step 1: Determine the total number of contacts who completed testing for M. tuberculosis infection. 

Do not include contacts who have a documented previous positive test result, have not 

completed testing, or who were not tested.

10 contacts completed testing. 

Step 2: Determine the number of contacts with a newly positive TST result.

7 of the 10 contacts who were tested had a positive TST result. 

Step 3: Divide the number of contacts with a newly positive test result by the total number of 

contacts that completed testing. 

7/10 = 0.70

Step 4: Multiply the number from Step 3 by 100%. 

0.70 x 100% = 70%

Answer: The TB infection prevalence for the contacts is 70%. 

TB Disease among Contacts Not Considered Priority

If a contact who was originally considered a low priority for 

assessment is found to have TB disease, this may indicate a 

need to expand the investigation to other low priority contacts. 

Generally, if any of the above evidence of recent transmission is 

found, expanding the contact investigation to include contacts 

at a lower priority should be considered. This may also indicate 

a need to re-interview the case to identify other contacts. If 

there is a plan to expand the investigation, the TB program 

still needs to continue to ensure that all priority contacts are 

properly assessed, managed, and treated. If this is a challenge, 

consultation and assistance from the next higher level of public 

health administration should be sought (e.g., the county health 

department would consult with the state health department). 

It is important to note that evidence of recent transmission 

may indicate an outbreak is occurring. If an outbreak is 

suspected, supervisory staff should immediately be alerted. 

More information about detecting TB outbreaks is presented in 

Module 9, Tuberculosis Outbreak Detection and Response. 

If there is a plan to expand 

the investigation, the 

TB program still needs 

to continue to ensure 

that all priority contacts 

are properly assessed, 

managed, and treated.

If an outbreak is suspected, 

supervisory staff should 

immediately be alerted.
53

Module 8—Contact Investigations for Tuberculosis 

Concluding a Contact Investigation

If no evidence of recent transmission is found, the investigation 

usually would not be expanded. 

A contact investigation can be concluded if

 All contacts have been assessed for TB infection and disease

 Contacts with LTBI have completed or are close to 

completing treatment

 No additional secondary cases of TB are found, either 

among identified contacts or through reviewing genotype 

information

Once the contact investigation is concluded, all investigation 

activities should be evaluated.

If no evidence of recent 

transmission is found, 

the investigation usually 

would not be expanded. 
54

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.15– 8.

8.15 List five indicators of recent transmission.

8.16 When can a contact investigation be concluded?

Answers to study questions are on pages 83– 89
55

Module 8—Contact Investigations for Tuberculosis 

Step 10: Evaluate the Contact Investigation Activities

An evaluation of the investigation activities should be conducted 

with or by a supervisor. The purpose of evaluating the activities 

of the investigation is to determine

 If the appropriate contacts were identified

 How many contacts were diagnosed with LTBI

 How many contacts with LTBI completed treatment 

 How many additional cases of TB disease were found 

 How many secondary cases of TB disease completed 

treatment

 How many contacts were not located

 How many contacts were located, but did not complete 

assessment 

 The timeliness of identifying and assessing contacts, and 

starting treatment if necessary

 If the contact investigation was performed in all necessary 

settings

 If the contact investigation was expanded appropriately

The answers to these questions will help determine how 

effectively and efficiently the contact investigation activities were 

conducted. 

Evaluation of activities should be conducted during case reviews 

and contact investigation team meetings throughout the contact 

investigation process. This will allow for any necessary immediate 

changes to improve the outcomes of the investigation.

At the end of the investigation, an evaluation can help identify 

areas in need of improvement. Additionally, many public 

health programs use a cohort review process. This allows for 

an opportunity to evaluate the contact investigation activities 

for each case within a certain time frame and identifies areas 

in need of improvement. Several resources are available about 

the TB cohort review process, including Understanding the TB 

Cohort Review Process: Instruction Guide and DVD Package. This 

resource is available from the CDC website.

Contact investigations are also an important indicator of the 

overall effectiveness of a TB control program. Thus, on a 

programmatic level, an aggregate of all contact investigation 

activities should be compiled and analyzed using data from the 

National Tuberculosis Indicators Project (NTIP).

An evaluation of the 

investigation activities 

should be conducted 

with or by a supervisor.

The cohort review process 

provides an opportunity 

to evaluate the contact 

investigation activities 

for each case within a 

certain time frame and 

identifies areas in need 

of improvement.
56

Module 8—Contact Investigations for Tuberculosis 

Evaluation of program performance ensures that resources are 

being used effectively and for the highest priority activities. 

Conducting contact investigations is a priority activity. 

Information from each contact investigation should be compiled 

separately and examined by management staff as part of 

ongoing part of program evaluation activities. 

The results of these program evaluations can be used to

 Determine program effectiveness

 Identify program strengths and areas in need of 

improvement

 Determine training needs

 Prioritize program activities and resources

In order to evaluate the contact investigation activities and 

overall program effectiveness, there should be a system in place 

to keep track of the number of contacts 

 Identified

 Assessed and yet-to-be assessed

 Diagnosed with LTBI or TB disease

 Started on treatment for LTBI or TB disease

 Who have completed treatment
57

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.17– 8.

8.17 What is the purpose of evaluating the TB contact investigation?

8.18 List the 10 steps of the systematic approach to contact investigation.

Answers to study questions are on pages 83– 89
Module 8—Contact Investigations for Tuberculosis 

58

Self-S

8

tudy Modules onTuberculosis 

Module

Assessment and Management of TB 

Contacts

This section provides more detailed information about Step 8 of 

the Systematic Approach to Contact Investigations. 

A contact assessment involves examining the contact for LTBI 

or TB disease. Health departments should have policies and 

procedures in place for the assessment and management of 

TB contacts. If a contact refuses to respond to requests for 

assessment, some states have communicable disease regulations 

or laws that set the precedents for legal action. 

What is Included in a Contact Assessment?

The major activities of the contact assessment include 

 Meeting with the contact

 Collecting and confirming information

 Maintaining confidentiality

 Conducting a medical evaluation

 Medical history

 HIV test 

 TB symptom review

 TST or IGRA to test for infection with M. tuberculosis

Meeting with Contacts

Investigators should meet in person and assess priority contacts 

within three working days of the contact being identified. 

When meeting with contacts, investigators should introduce 

themselves and explain that the purpose of the visit is to discuss 

a health matter. Before discussing any specific information, the 

investigator should verify the contact’s identity. The discussion 

should be continued at a place that allows for privacy. 

The investigators should inform the contact that he or she 

may have been exposed to TB and will need to be medically 

evaluated for TB disease or LTBI. The investigators should 

explain TB disease and how it is transmitted, diagnosed, and 

treated. TB educational tools can be used to help answer any 

questions the contact may have about TB disease or LTBI. 

Health departments 

should have policies 

and procedures in place 

for the assessment 

and management 

of TB contacts.

Investigators should meet 

in person and assess 

priority contacts within 

three working days of the 

contact being identified.
59

Module 8—Contact Investigations for Tuberculosis 

Collecting and Confirming Information

Contacts generally do not need to undergo the same in-depth 

interviewing process as TB cases. Contacts should be asked 

if they have any signs and symptoms of TB disease; or if they 

have a history of TB disease or LTBI, whether they completed 

treatment for either. It may be useful to ask the contact a few 

questions to confirm where they spent time and if they have 

any acquaintances who have signs and symptoms of TB. These 

questions may provide information about additional contacts 

and places the case had not mentioned.

Maintaining Confidentiality

When meeting with contacts, the investigator should ensure that 

confidentiality is maintained by not revealing any personally 

identifying information about the case or any specific details 

about the exposure. Additionally, the investigator should 

be careful not to accidentally reveal clues about the case. 

Confidentiality should not be violated even if contacts refuse to 

be evaluated. 

The following strategies can be used to protect confidentiality 

when meeting with contacts:

 Use gender-neutral language. For example, “Somebody was 

diagnosed with TB and they were concerned about you” 

instead of “A woman was diagnosed with TB and she was 

concerned about you.”

 Do not mention the case’s healthcare worker, place and 

dates of diagnosis, or hospitalization. 

 Do not mention the environment in which the exposure 

occurred. For example, “You have been around somebody 

who has TB” instead of “You have been around somebody 

at work who has TB.”

 Do not confirm the name of the case if the contact correctly 

guesses his or her identity.

The investigator should also let the contact know that any 

information provided will remain confidential.

Conducting a Medical Evaluation

The contact’s medical evaluation may occur in the field or at the 

clinic. The following are components of a medical evaluation for 

contacts:

 Medical and social history

 HIV test

 TB symptom review

 TST or IGRA

Contacts should be asked 

if they have any signs and 

symptoms of TB disease; 

or if they have a history 

of TB disease or LTBI, 

whether they completed 

treatment for either.

When meeting with 

contacts, the investigator 

should ensure that 

confidentiality is 

maintained by not 

revealing any personally 

identifying information 

about the case or any 

specific details about 

the exposure.
60

Module 8—Contact Investigations for Tuberculosis 

Medical and Social History

The medical history of the contact should include information 

about prior LTBI or TB diagnosis, treatment, or exposure, and 

medical or social risk factors for progression to TB disease. 

HIV Test

Contacts should be offered an HIV test if their status is 

unknown, even if the person is at low risk for HIV. 

TB Symptom Review

All contacts should be assessed for symptoms of TB disease. 

General symptoms of TB disease include 

 Fever 

 Chills 

 Night sweats 

 Weight loss 

 Appetite loss 

 Fatigue 

 Malaise 

Symptoms of pulmonary TB disease include 

 Cough lasting 3 weeks or longer 

 Chest pain 

 Coughing up blood or sputum (phlegm) 

Symptoms of extrapulmonary TB disease depend on the part of 

the body that is affected. For example 

 TB disease in spine may cause back pain 

 TB disease in kidneys may cause blood in urine 

 TB disease in lymph nodes may cause swelling in the neck

 TB disease of the larynx may cause hoarseness

Contacts with symptoms of TB disease should be further 

evaluated with a chest x-ray and three respiratory specimens 

for AFB smear and culture. For more information on diagnosing 

TB disease, please refer to Module 3, Targeted Testing and the 

Diagnosis of Latent Tuberculosis Infection and Tuberculosis 

Disease.

Contacts with symptoms 

of TB disease should be 

further evaluated with 

a chest x-ray and three 

respiratory specimens for 

AFB smear and culture.
61

Module 8—Contact Investigations for Tuberculosis 

TST or IGRA

Contacts should be tested for M. tuberculosis infection using 

either a TST or an IGRA. Contacts who have a history of TB 

disease or a previous positive TST or IGRA result generally 

do not need to be retested for M. tuberculosis infection. They 

should be assessed for signs and symptoms of TB disease and 

asked about prior treatment for LTBI or TB disease. 

For those contacts given a TST or tested with an IGRA, a repeat 

test may be needed depending on the result of the test. The 

same method of testing for infection should be used for both the 

initial and repeat test (i.e., if the first test was a TST, the repeat 

test should be a TST). For more information on administering 

and interpreting TST or IGRA results, refer to Module 3, Targeted 

Testing and the Diagnosis of Latent Tuberculosis Infection and 

Tuberculosis Disease.

Initial Negative TST or IGRA

If the initial TST or IGRA is negative, a repeat test is needed 

if the initial test was given less than 8 to 10 weeks since the 

contact’s last exposure to the case. This is because it can take 

2 to 8 weeks after being infected with M. tuberculosis for the 

body’s immune system to mount a response detectable by the 

tests. The time between the contact’s last exposure to the case 

and when a TST or IGRA can reliably detect infection is referred 

to as the window period. 

The repeat test should be conducted 8 to 10 weeks after the last 

exposure to the case. If the result of the repeat test is positive, 

and TB disease is ruled out, the contact should be classified as 

recently infected and followed-up and treated appropriately. 

Figure 8.8 shows an example of calculating the window period 

and determining when a repeat test should occur for contacts 

with an initial negative test result. 

Initial Positive TST or IGRA

If the initial TST or IGRA is positive, the contact should be 

considered positive for M. tuberculosis infection and a repeat 

test is unnecessary, even if it has been less than 8 weeks since 

the last exposure to the case. A TST result of 5 mm or more is 

considered a positive result for a TB contact. The interpretation 

of IGRA results is the same for all patients; no cut-points are 

defined differently for contacts. TB disease should first be ruled 

out before initiating LTBI treatment.

Contacts should be tested 

for M. tuberculosis

infection using either 

a TST or an IGRA.

If the initial TST or IGRA 

is negative, a repeat test 

is needed if the initial test 

was given less than 8 to 10 

weeks since the contact’s 

last exposure to the case.

The time between the 

contact’s last exposure 

to the case and when a 

TST or IGRA can reliably 

detect infection is referred 

to as the window period.

If the initial TST or IGRA 

is positive, the contact 

should be considered 

positive for M. tuberculosis

infection and a repeat 

test is unnecessary, even 

if it has been less than 

8 weeks since the last 

exposure to the case.
62

Module 8—Contact Investigations for Tuberculosis 

Figure 8.8—Example of calculating the window period. If a contact’s last exposure to a TB case was July 

1st, and he or she had a negative TST or IGRA on August 1st, a second TST or IGRA should be done between 

September 1st and September 15th (8 to 10 weeks after July 1st).

Management and Treatment of Contacts

For a contact investigation to be considered successful, contacts 

who have TB disease or LTBI should complete treatment. The 

appropriate management and treatment of these contacts is the 

responsibility of the health department.

Management and Treatment of Contacts with TB Disease

Contacts who have TB disease should be managed and 

treated in accordance with CDC treatment guidelines. DOT 

and the use of incentives and enablers are recommended to 

support adherence and achieve completion of treatment. For 

more information about the treatment of TB disease, refer to 

Module 4, Treatment of Tuberculosis Infection and Tuberculosis 

Disease. For detailed recommendations for the treatment of 

TB disease, refer to the Official American Thoracic Society/

Centers for Disease Control and Prevention/Infectious Diseases 

Society of America Clinical Practice Guidelines: Treatment of 

Drug-Susceptible Tuberculosis. It is important to remember that 

for each contact who is found to have infectious TB disease, a 

separate contact investigation needs to be started immediately. 

Contacts who have 

TB disease should be 

managed and treated 

in accordance with CDC 

treatment guidelines.

Contact’s last 

exposure to the case

Initial TST or IGRA

is negative

Only 4 weeks have passed since 

contact’s last exposure to the case Contact should have 

repeat TST or IGRA 

8 to 10 weeks after last 

exposure to the case

June

15

July

1

July

15

August

15

August

1

September

1

September

15

September

30

Calculation of the Window Period

The window period is the time between the contact’s last exposure to the case 

and when a TST or IGRA can reliably detect infection, usually 8 to 10 weeks later. 
63

Module 8—Contact Investigations for Tuberculosis 

Management and Treatment of Contacts with LTBI

Once TB disease has been ruled out, treatment for LTBI 

should be offered to all contacts with a positive TST or IGRA, 

unless there is a compelling reason not to do so. Treatment 

should be offered regardless of whether the contact has 

received the BCG vaccine in the past. Treatment should also 

be offered to contacts with a prior positive TST or IGRA who 

did not complete treatment for LTBI.

In general, contacts with a positive TST or IGRA and a 

documented history of LTBI treatment completion do not 

need to be re-treated. However, in some circumstances, repeat 

treatment for LTBI may be advisable based on the contact’s 

risk for re-infection with M. tuberculosis and progression to 

TB disease. 

Special Considerations in TB Contact Assessment 

and Management 

Window Period Prophylaxis 

Contacts Younger than 5 Years of Age

Because of their age, young children with M. tuberculosis

infection are known to have been recently infected, and thus 

are at a high risk of progressing to TB disease. Young children 

are also more likely than older children and adults to develop 

life-threatening forms of TB disease, especially meningeal and 

disseminated disease. 

Children younger than 5 years of age should be medically 

assessed, including a chest x-ray, regardless of a history of 

LTBI or TB disease treatment or an initial negative TST or 

IGRA result. Since TB disease may present differently in 

children than adults, clinicians with pediatric TB disease 

experience should be consulted during the assessment and 

medical evaluation process.

Once TB disease has been ruled out, children younger than 

5 years of age should receive LTBI treatment, even if their 

initial TST or IGRA result is negative. This is called window 

period prophylaxis. 

Once TB disease has been 

ruled out, treatment for 

LTBI should be offered 

to all contacts with a 

positive TST or IGRA, unless 

there is a compelling 

reason not to do so.

Once TB disease has been 

ruled out, children younger 

than 5 years of age should 

receive LTBI treatment, 

even if their initial TST or 

IGRA result is negative. 

This is called window 

period prophylaxis. 
64

Module 8—Contact Investigations for Tuberculosis 

Window period prophylaxis can be stopped if ALL of the 

following conditions are met: 

 The child is at least 6 months of age

 The second TST or IGRA is negative

 The second TST or IGRA was done at least 8 weeks 

after the child was last exposed to an adult with 

infectious TB disease

If the second TST or IGRA is positive, a full course of LTBI 

treatment should be continued and completed.

Contacts with HIV Infection

Because of their weakened immune systems, persons living with 

HIV are at high risk for rapidly developing TB disease. Contacts 

known or suspected to be HIV-infected should be medically 

evaluated, including a chest x-ray, to rule out TB disease. Expert 

consultation should be sought for contacts with HIV infection 

who need TB treatment.

Once TB disease has been ruled out, HIV-infected contacts 

should receive window period prophylaxis for LTBI regardless 

of their initial IGRA or TST result. In general, treatment of LTBI 

should be continued even if the second TST or IGRA result is 

negative. This is because some HIV-infected contacts may not be 

able to produce a positive TST or IGRA result because of their 

weakened immune systems. Clinicians should use TB exposure 

information (e.g., frequency, duration, and infectiousness of 

the case) to guide their decision on whether to continue or 

discontinue LTBI treatment. 

Contacts with Other Immune Impairment

Expert consultation should be sought to determine if contacts 

with immune impairments other than HIV infection 

(e.g., contacts taking immunosuppressive therapies) could 

benefit from window period prophylaxis, regardless of their 

initial TST or IGRA results. Offering treatment for presumed 

M. tuberculosis infection may be considered if the likelihood 

of infection is high, based on the circumstances of the exposure 

and prevalence of TB infection among other contacts.

Table 8.5 summarizes the CDC recommendations for the 

prophylactic treatment of presumed infection with 

M. tuberculosis for contacts younger than 5 years of age 

and contacts with HIV infection.

Once TB disease has been 

ruled out, HIV-infected 

contacts should receive 

window period prophylaxis 

for LTBI regardless of their 

initial IGRA or TST result.
65

Module 8—Contact Investigations for Tuberculosis 

Table 8.5 Recommendations for Prophylactic Treatment of Presumed Infection with M. tuberculosis for 

Contacts Younger than 5 Years of Age and Contacts with HIV Infection

Prophylactic 

Treatment

Contacts Less than 

6 Months of Age*

Contacts Older than 

6 Months but Younger than 5 

Years of Age

Contacts with HIV 

(any age)

When to 

start 

As soon as possible if medical assessment and chest x-rays show no evidence of current TB 

disease, even if initial TST or IGRA result is negative

When to 

stop

Contact reaches 6 months of age 

and TST or IGRA done 8 to 10 weeks 

after last exposure is negative

or

Once a full course of treatment for 

LTBI is completed

TST or IGRA done 8 to 10 weeks 

after last exposure is negative

or

Once a full course of treatment 

for LTBI is completed

Once a full course of 

treatment for LTBI is 

completed

* Negative TST and IGRA results can be unreliable in children younger than 6 months of age.

Contacts to Drug-Resistant TB

Treatment regimens for contacts should reflect the drug 

susceptibility patterns of the M. tuberculosis isolate of the 

presumed source case. Selection of treatment regimens for 

contacts to drug-resistant TB requires expert consultation. 

Additionally, supporting adherence to LTBI treatment for 

infected contacts of drug-resistant TB is very important. 

Consideration should be given to providing DOT and using 

incentives and enablers for contacts believed to be infected with 

drug-resistant M. tuberculosis. 

Contacts of Isoniazid-Resistant TB 

If a person is a contact to isoniazid-resistant TB, a 4-month 

regimen of daily rifampin may be recommended. In situations 

where rifampin cannot be used, rifabutin may be substituted. 

Contacts of Multidrug-Resistant TB

The risk for developing TB disease should be considered before 

recommending LTBI treatment for contacts to multidrug-resistant 

(MDR) TB. MDR-TB contacts may be treated for 6–12 months or 

they can be observed for signs and symptoms of disease without 

treatment. If treating an MDR-TB contact for LTBI, an alternative 

regimen of drugs to which the M. tuberculosis isolate is known 

to be susceptible should be used. Immunocompromised 

contacts should be treated for 12 months. All persons with 
66

Module 8—Contact Investigations for Tuberculosis 

suspected MDR LTBI should be followed and observed for 

signs and symptoms of TB disease for 2 years, regardless of the 

treatment regimen. An expert in the treatment of MDR TB should 

be consulted. 

For more information about the treatment of LTBI, refer to 

Module 4, Treatment of Latent Tuberculosis Infection and 

Tuberculosis Disease. For detailed recommendations for the 

treatment of LTBI, refer to the CDC’s Targeted Tuberculin Testing 

and Treatment of Latent Tuberculosis Infection and Update of 

Recommendations for Use of Once-Weekly Isoniazid-Rifapentine 

Regimen to Treat Latent Mycobacterium tuberculosis Infection.

Figure 8.9 on page 67 diagrams the assessment and management 

process of TB contacts. This figure is presented as a guide only, 

and is not meant to substitute for careful consideration of each 

contact’s risk of infection and progression to TB disease.

Data Management and Collection for Contacts

To ensure that contacts are managed and followed-up 

appropriately, it is essential to have a good data collection and 

management system. Data should be recorded throughout the 

contact assessment and management process. This information 

will also be used to evaluate the success of the contact 

investigation. 

Information collected from each contact may vary by jurisdiction. 

Each jurisdiction may have their own forms for collecting 

information about contacts and for summarizing investigation 

findings. Some health jurisdictions have a separate record for 

each contact, while others have multiple contacts recorded on a 

single form that is attached to the index case records. 

Table 8.6 lists information that should be collected about each 

contact. Some of this information will be collected from the case 

during the interview, and some of it will be collected from the 

contact during the investigation process. 

To ensure that contacts are 

managed and followedup appropriately, it is 

essential to have a good 

data collection and 

management system.
67

Module 8—Contact Investigations for Tuberculosis 

Figure 8.9—Assessment and management of TB contacts.

Does the contact have TB symptoms or risk factors for rapid progression to TB disease?

Review treatment 

history; consider 

clinical evaluation 

and treatment

Evaluation for infection with M. tuberculosis and TB disease 

including physical examination, chest x-rays, AFB smear 

and culture for TB, and TST or IGRA if not already done

Assessment is complete for contacts aged 

6 months or older. Consider presumptive LTBI 

treatment for contacts with HIV infection. 

Provide window period prophylaxis until child has 

reached 6 months of age and 8 to 10 weeks have 

passed since last exposure to the infectious case.

Repeat symptom assessment and testing for infection with M. tuberculosis 

8 to 10 weeks after last exposure to case. If the contact has symptoms of 

TB disease or the TST or IGRA is positive, a medical evaluation is necessary.

No Yes

No Yes

No Yes

Review medical history

Administer TST or IGRA

Prior TB disease or positive TST or IGRA? 

Positive TST or IGRA result?

Have 8 to 10 weeks passed since contact’s last exposure to the infectious case?

No Yes

Is contact younger than 5 years of age?

No

No Yes

Yes

Does contact have TB disease? 

No Yes

Treat 

for TB 

disease

Treat for 

LTBI

LTBI?
68

Module 8—Contact Investigations for Tuberculosis 

Table 8.6 Information to Collect About Each Contact

Information to Obtain from the Case

 Name(s)

 Address(es) and telephone number(s)

 Gender

 Physical description

 Contact’s relationship to the case

 Date of last exposure to the case

 Location where exposure occurred

 Frequency and durations of the exposure(s)

 Physical proximity between the contact and the case during the exposure

Information to Obtain from the Contact

 Basic demographic information, including name(s), date of birth

 Preferred language

 Address(es) and telephone number(s)

Information to Obtain During the Assessment Process

 Date and location of the assessment

 Risk factors for development of TB disease

 Symptoms of TB disease, if any 

 TST or IGRA dates and results

 Chest x-ray dates and results

 HIV infection status

 Final diagnostic classification

 Treatment and other follow-up
69

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.19– 8.

8.19 What are the major activities of the contact assessment?

8.20 What is the window period?

8.21 What is window period prophylaxis? Which contacts should receive window period 

prophylaxis?

Answers to study questions are on pages 83– 89
70

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

Priya is a 34-year-old woman who was diagnosed with infectious TB disease. As part of her 

contact investigation, you identified the following priority contacts: 

 Naveen (husband, 35 years old)

 Sanjay (son, 3 years old)

 Asha (close friend, 37 years old)

 Paul (co-worker, 52 years old)

 Marie (co-worker, 43 years old) 

Five weeks have passed since the contacts were last exposed to Priya while she was infectious. 

These contacts (a total of 5) have been assessed by the contact investigation team. None of the 

contacts were found to have TB symptoms. 

The skin test results were as follows:

 Naveen: 11 mm

 Sanjay: 0 mm

 Asha: 5 mm

 Paul: 3 mm

 Marie: 0 mm 

What follow-up testing and treatment are needed for contacts with a positive skin test?

Should any follow-up testing be given to contacts with a negative skin test?

Which contacts should receive a repeat skin test? When should the repeat test be performed?

Answers to case studies are on pages 90– 98
Module 8—Contact Investigations for Tuberculosis 

71

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8

tudy Modules onTuberculosis 

Module

TB Contact Investigations in 

Congregate Settings

This section highlights challenges and solutions to conducting 

TB contact investigations in congregate settings. Local public 

health programs should consult with the next higher level of 

public health administration if needed.

What is a Congregate Setting?

A congregate setting is a setting in which a group of persons 

reside in close physical proximity. Examples of congregate 

settings include

 Schools

 Shelters

 Nursing homes

 Correctional facilities

 Workplaces

 Hospitals or other healthcare settings

How are Contact Investigations Conducted in 

Congregate Settings?

Contact investigations involving congregate settings should 

follow the systematic contact investigation process presented 

on pages 15–56 of this module. However, there may be 

some additional challenges to consider when conducting an 

investigation in a congregate setting, including 

 Large numbers of contacts

 Incomplete data for determining which contacts should be 

prioritized for assessment

 Difficulties related to maintaining confidentiality

 Incomplete information about contacts’ names and locating 

information

 A need to collaborate with officials and administrators who 

are not familiar with TB

 Media interest, particularly for investigations involving 

schools or worksites

 Political implications of negative publicity related to TB

 Legal implications for the facility 
72

Module 8—Contact Investigations for Tuberculosis 

To effectively address these potential challenges, contact 

investigations involving congregate settings often require 

additional resources. This is to ensure that other essential 

TB control activities are not disrupted.

An initial notification of the need for a contact investigation 

in the congregate setting can occur by phone call. This call 

should also be used to schedule an in-person meeting with 

administrators to discuss the contact investigation process. 

At the meeting, the following items should be discussed:

 Purpose of the meeting

 Basic TB concepts 

 Confidentiality issues 

 Infectious period 

 Total number of persons in the congregate setting 

 Process of identifying, prioritizing, and testing contacts

 Potential media interest

Because of confidentiality issues, contact investigators should 

be careful not to reveal personally identifying information 

to administrators without the case’s knowledge and without 

reviewing local jurisdiction policy and consultation with a 

supervisor at the TB program. In some situations, a signed 

confidentiality agreement from the administrators or consent 

from the case may be needed.

Whenever possible, health departments should collaborate with 

administrators from congregate settings to identify opportunities 

for efficient and convenient assessment of contacts and 

delivery of treatment to contacts for LTBI or TB disease. Onsite 

assessment is typically the most effective way to reach contacts. 

If such an approach is not possible, special arrangements 

may be necessary to ensure priority contacts are completely 

assessed. For example, health departments may need to extend 

clinic hours or hire additional staff. As a last resort, the health 

department can notify contacts in writing to seek assessment for 

TB with their own healthcare provider.

Correctional Facilities

Investigations involving correctional facilities can be particularly 

challenging because of crowded conditions, large numbers 

of contacts (both inmates and correctional employees), 

poor ventilation, incomplete records, inaccessible records, 

misconceptions about TB and its transmission, slow access to 

medical care, and high turnover or movement of inmates.

To effectively address 

potential challenges, 

contact investigations 

involving congregate 

settings often require 

additional resources to 

ensure that other essential 

TB control activities 

are not disrupted.

Whenever possible, 

health departments 

should collaborate with 

administrators from 

congregate settings to 

identify opportunities 

for efficient and 

convenient assessment 

of contacts and delivery 

of treatment to contacts 

for LTBI or TB disease.
73

Module 8—Contact Investigations for Tuberculosis 

Identifying contacts requires that investigators collect information 

on where the case spent time, as well as any work assignments 

and activities within the correctional facility. Because of the 

potential intensity of exposure within a crowded or poorly 

ventilated space, contacts should be considered high priority 

unless records indicate a brief exposure. Investigators should 

also locate priority contacts who have been transferred, released, 

or paroled. For contacts who start treatment, it is important to 

have follow-up supervision to ensure completion of treatment, 

particularly if the contact has been released or paroled. 

Schools 

Contact investigations in schools typically feature a potentially 

large number of contacts and can come with unique challenges 

because children are involved. Contact investigations based 

in schools may generate community and media attention. 

Therefore, TB control officials should anticipate media coverage 

and plan a collaborative strategy with the school to address 

parental and community concerns. Often, the concern from 

parents and the community can lead to the entire school being 

tested, regardless of the priority level of the contact. Some 

parents or guardians may not offer consent to have their children 

assessed for TB. In these circumstances, the health department 

should be prepared to consult with legal experts if necessary. 

Identifying and assigning priorities to contacts may be 

challenging as it can be difficult to define the duration 

and proximity of exposure to the case. If available, contact 

investigators should refer to class assignments, extramural 

activities, and bus rosters to assist in prioritization. Additionally, 

interviews with the case, his or her parents or guardians, and 

school officials can elicit more information.

Homeless Shelters

Contact investigations involving shelters and homeless persons 

can be complicated because they often require assessment of a 

large number of contacts. Additionally, these investigations can 

be difficult because of the transient characteristics and lifestyle 

of some homeless persons. Locating the contacts of a homeless 

TB case can be challenging because of the following potential 

characteristics associated with homeless persons: 

 Migration from one shelter or jurisdiction to another

 Mental illnesses

 Alcohol or drug use

 Periodic incarceration

 Preexisting medical conditions (e.g., HIV)

Contact investigations 

in schools typically 

feature a potentially large 

number of contacts and 

can come with unique 

challenges because 

children are involved.
74

Module 8—Contact Investigations for Tuberculosis 

To help identify contacts, investigators should work with the 

administrators at homeless shelters. Some shelters may maintain 

daily sign-in sheets or logs. These may be used to help identify 

persons who were at the shelter at the same time as the case. 

However, it is important to note that in some jurisdictions, this 

information may be restricted by law.

To identify and assess additional contacts who may not have 

been named by the case, a location-based approach may be 

useful (refer to page 45 of this module).
75

Module 8—Contact Investigations for Tuberculosis 

Study Question 8.22

8.22 List five challenges associated with conducting contact investigations in 

congregate settings.

Answers to study questions are on pages 83– 89
Module 8—Contact Investigations for Tuberculosis 

76

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Module

Conducting Source Case Investigations

What is a Source Case Investigation?

A source case is a person with TB disease who is responsible 

for transmitting M. tuberculosis to another person or persons. 

A source case investigation is a method used to identify 

source cases. 

The purposes of a source case investigation are to determine 

 Who transmitted M. tuberculosis to a child or to a group 

of persons (such as healthcare workers or correctional 

facility inmates and staff) who have been recently infected 

with M. tuberculosis

 Whether the source case is still infectious

 Whether the source case was reported to the health 

department 

 Whether any other persons were infected by the source case

 The drug susceptibility test results and genotyping results of 

the source case who transmitted TB to a child

When Should a Source Case Investigation 

be Conducted?

Because source case investigations require a lot of time and 

effort and generally do not result in finding the source case or 

additional priority contacts, a health department must determine 

when it is necessary to conduct a source case investigation. 

State or local policies should be consulted for the specific 

criteria for conducting a source case investigation. A source case 

investigation could be considered in the following situations:

 A child 5 years of age or younger has been diagnosed with 

TB disease

 An infant 2 years of age or younger has been diagnosed 

with LTBI

 Healthcare settings where serial TB testing indicates recent 

M. tuberculosis infection in a healthcare worker

 Correctional facilities (e.g., jails, prisons) where TB testing 

indicates an increase in M. tuberculosis infection among 

inmates or staff

A source case is a person 

with TB disease who is 

responsible for transmitting 

M. tuberculosis to another 

person or persons. A 

source case investigation 

is a method used to 

identify source cases. 
77

Module 8—Contact Investigations for Tuberculosis 

TB disease in children 5 years of age or younger and LTBI in 

infants 2 years of age and younger indicates that M. tuberculosis

was recently transmitted. If exposure to an infectious case is 

unknown, a source case investigation may help find a person 

with undiagnosed TB disease who had contact with the child. It 

may also find additional contacts who have recent M. tuberculosis

infection from the same source case and need medical attention.

In healthcare settings, if serial TB testing detects a change in 

a healthcare worker’s TST or IGRA status from negative to 

positive, this could indicate recent TB transmission. If the source 

of exposure is unknown, a source case investigation can help 

determine whether there is unrecognized infectious TB within 

the healthcare facility. For more detailed information, please 

refer to the CDC’s Guidelines for Preventing the Transmission of 

Mycobacterium tuberculosis in Health-Care Settings, available 

from the CDC website (www.cdc.gov/tb).

If TB testing in correctional facilities indicates an increase in 

M. tuberculosis infection among inmates or employees, a source 

case investigation should be considered to determine if there is a 

case of unrecognized infectious TB in the facility.

How Are Source Case Investigations Conducted?

A source case investigation moves in the opposite direction of a 

contact investigation, but the same principles and investigative 

skills apply. A source case investigation usually begins by 

reviewing existing information (e.g., medical records) to confirm 

that the person has been recently infected with M. tuberculosis. 

Once it has been determined that the person has been recently 

infected, the next step is to determine potential source cases. 

This is done by interviewing the person who has been recently 

infected or by conducting proxy interviews if the source case 

investigation involves a young child. 

Conducting Source Case Investigations Involving Children

If the source case investigation is for a child, their parent, 

guardian, or someone else who knows the child’s lifestyle 

should be interviewed. The principles of a source case interview 

are similar to the standard TB contact investigation interview; 

however, the emphasis is on finding the source of TB instead of 

finding contacts to the case. 

A source case investigation 

moves in the opposite 

direction of a contact 

investigation, but the 

same principles and 

investigative skills apply.

If the source case 

investigation is for a child, 

their parent, guardian, 

or someone else who 

knows the child’s lifestyle 

should be interviewed.
78

Module 8—Contact Investigations for Tuberculosis 

During the interview, the investigators should ask about whom 

the child has spent time with at the following locations or 

activities:

 Home (e.g., persons living in the household, frequent 

visitors, babysitters) 

 School

 Day care (both inside the home and outside the home) 

 Car pools or buses

 Play groups 

 Recreational activities 

 Places of recent travel 

Additionally, investigators should ask if any person whom the 

child has spent time with has shown symptoms of TB disease. 

Once potential sources have been identified, they should 

be located and assessed. Assessments during source case 

investigations typically focus on symptom reviews, potentially 

followed by chest x-rays and respiratory specimen collection 

for AFB smear and culture. Compared to a contact investigation, 

less emphasis is usually placed on testing for infection 

unless investigators are concerned about potential ongoing 

transmission. 

Conducting Source Case Investigations Involving 

Healthcare Workers and Correctional Facility Staff 

or Inmates 

When a source case investigation involves a person who is 

thought to have been infected at a healthcare or correctional 

setting, investigators should determine the timeframe during 

which the person may have been infected. This time frame is 

referred to as the likely exposure period. The exposure period 

usually begins 8 weeks prior to the most recent negative TST or 

IGRA result and ends 2 weeks before the first positive TST or 

IGRA result. The exposure period should be used to determine 

potential source cases. The persons infected with M. tuberculosis

should be interviewed to identify the following persons or 

locations visited during the exposure period:

 Persons with symptoms of infectious TB disease 

 Persons at increased risk for having TB disease 

 Locations where they spent time during the exposure period 

where source cases may also have been present 

In addition to interviewing newly infected persons, investigators 

can also identify potential source cases by determining which 

areas of the facility are associated with the new TB infections. 
79

Module 8—Contact Investigations for Tuberculosis 

Investigators may also review medical records at the facility 

for recent respiratory illnesses that may have been infectious 

TB disease, but were diagnosed as something else. Once the 

potential source cases have been determined, they should be 

located and assessed for TB disease. For inmates who have been 

in more than one facility, efforts should be made to collaborate 

with all facilities affected.

Data in Source Case Investigations

If source case investigations are conducted, data should be 

monitored to determine the value of the investigations. Data 

should include

 Total number of source case investigations conducted

 Number of persons assessed for TB disease

 Number of times a source case was identified

 Whether identified source cases were previously known to 

the health department or if they were detected as a direct 

result of a source case investigation

How Can TB Genotyping Information Contribute to 

a Source Case Investigation?

TB genotyping can contribute to source case investigations by 

either confirming or disproving a named person as the source 

case. Additionally, genotyping can identify potential source 

cases that were not originally identified in the investigation.

For example, if a source case investigation is conducted 

for a child or another case with active TB disease, their TB 

genotype information can be compared to other recent cases 

in the jurisdiction to determine if the genotypes match. If the 

genotypes match, this could mean that these cases were linked 

in the same chain of transmission. To confirm this, the medical 

records of the recent case should be reviewed and discussions 

with contact investigators of the case should be held to 

determine if there were any connections between these two cases. 

When a suspected source case is identified, genotyping can 

support evidence of the transmission link to the case if the 

isolates from both have matching genotypes. If the investigation 

yields no suspected source case, a review of all genotyping 

results from cases living in the same region as the case may 

identify a genotype match.

TB genotyping can 

contribute to source case 

investigations by either 

confirming or disproving 

a named person as the 

source case as well as 

identifying potential 

source cases that were 

not originally identified 

in the investigation.
80

Module 8—Contact Investigations for Tuberculosis 

Study Questions 8.23– 8.

8.23 What is a source case investigation?

8.24 How can genotyping contribute to source case investigations?

Answers to study questions are on pages 83– 89
81

Module 8—Contact Investigations for Tuberculosis 

Case Study 8.

Jung is a 3-year-old child who has been diagnosed with TB meningitis. Jung, his parents, and 

his paternal grandmother immigrated to the United States from China one year ago. 

Should a source case investigation be conducted?

What information should you try to obtain? 

Answers to case studies are on pages 90– 98
82

Module 8—Contact Investigations for Tuberculosis 

Additional Resources

1. CDC. Effective TB Interviewing for Contact Investigation: DVD. 

Atlanta, GA: Department of Health and Human Services, CDC; 

2006. www.cdc.gov/tb/publications/guidestoolkits/Interviewing/

default.htm.

2. CDC. Effective TB Interviewing for Contact Investigation: 

Self-Study Modules. Atlanta, GA: Department of Health and 

Human Services, CDC; 2006. www.cdc.gov/tb/publications/

guidestoolkits/Interviewing/default.htm. 

3. CDC. Guidelines for Preventing the Transmission of 

Mycobacterium tuberculosis in Health-Care Settings, 2005. 

MMWR 2005; 54 (No. RR-17). www.cdc.gov/mmwr/preview/

mmwrhtml/rr5417a1.htm?s_cid=rr5417a1_e. 

4. CDC. Guidelines for the Investigation of Contacts of Persons with 

Infectious Tuberculosis: Recommendations from the National 

Tuberculosis Controllers Association and CDC. MMWR 2005; 54 

(No. RR-15). www.cdc.gov/mmwr/preview/mmwrhtml/rr5415a1.htm. 

5. CDC. Targeted Tuberculin Testing and Treatment of Latent 

Tuberculosis Infection. MMWR 2000; 49 (No. RR-06). 

www.cdc.gov/MMWR/preview/MMWRhtml/rr4906a1.htm. 

6. CDC. TB Contact Investigation Interviewing Skills Course. Atlanta, 

GA: Department of Health and Human Services, CDC; 2013. 

http://www.cdc.gov/tb/education/skillscourse/default.htm

7. CDC. TB Genotyping Information Management System 

(TB GIMS). Atlanta, GA: Department of Health and Human 

Services, CDC; 2009. www.cdc.gov/tb/publications/factsheets/

statistics/TBGIMS.pdf. 

8. CDC. Update of Recommendations for Use of Once-Weekly 

Isoniazid-Rifapentine Regimen to Treat Latent Mycobacterium 

tuberculosis Infection. MMWR 2018; 67:723–726. www.cdc.gov/

mmwr/volumes/67/wr/mm6725a5.htm?s_cid=mm6725a5_w

9. CDC. Understanding the TB Cohort Review Process: Instruction 

Guide. Atlanta, GA: Department of Health and Human Services, 

CDC; 2006. www.cdc.gov/tb/education/cohort.htm. 

10. Global TB Institute at Rutgers, the State University of New Jersey. 

TB Interviewing for Contact Investigation: A Practical Resource 

for the Healthcare Worker; 2008. http://globaltb.njms.rutgers.

edu/educationalmaterials/productfolder/tbinterviewing.php. 

11. Nahid P, Dorman SE, Alipanah N, Barry PM, Brozek JL, 

Cattamanchi A, Chaisson LH, Chaisson RE, Daley CL, Grzemska 

M, Higashi JM, Ho CS, Hopewell PC, Keshavjee SA, Lienhardt C, 

Menzies R, Merrifield C, Narita M, O’Brien R, Peloquin CA, Raftery 

A, Saukkonen J, Schaaf HS, Sotgiu G, Starke JR, Migliori GB, 

Vernon A. Official American Thoracic Society/Centers for Disease 

Control and Prevention/Infectious Diseases Society of America 

Clinical Practice Guidelines: Treatment of Drug-Susceptible 

Tuberculosis. Clinical Infectious Disease 2016:1–49. http://cid.

oxfordjournals.org/content/early/2016/07/20/cid.ciw376.full.
83

Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions

8.1 What is a TB contact investigation?

A TB contact investigation is a systematic process to

 Identify persons (contacts) exposed to a person with infectious 

TB disease (a case)

 Assess contacts for infection with M. tuberculosis and TB disease 

 Provide appropriate treatment for contacts with LTBI or TB disease 

8.2 What are the goals of a TB contact investigation?

The goals of a TB contact investigation are to successfully stop TB transmission and to 

prevent future cases and outbreaks of TB disease.

8.3 Which TB cases require a contact investigation?

A contact investigation is required for all confirmed cases that have infectious forms of 

TB disease (e.g., TB disease of the lungs, airways, or larynx). 

The contact investigation process should be started for persons suspected of having 

infectious TB disease, even before confirmation. This includes persons with positive 

sputum smears and a positive nucleic acid amplification test result. For persons with 

positive sputum smears and a negative nucleic acid amplification test result, a contact 

investigation is not indicated.

For suspect cases with negative sputum smears or sputum smears not performed, the 

contact investigation process should be started if the case has abnormal chest x-ray 

findings consistent with TB disease. 

For suspect cases with negative sputum smear results and no pulmonary cavities, a 

contact investigation should only be considered for certain circumstances, such as if the 

suspect was identified during an outbreak or source case investigation that included 

vulnerable or susceptible contacts. 

If it is later determined that the suspect case does not have infectious TB disease, the 

contact investigation should be stopped.

8.4 Who is responsible for conducting TB contact investigations?

In the United States, state and local health departments are legally responsible for the 

prevention and control of TB in their communities. Thus, they are accountable for 

ensuring contact investigations are performed for TB cases reported in their jurisdictions, 

even when patients are receiving care outside the health department.
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.5 Which TB contact investigations should be given priority? 

In general, priority should be given to contact investigations involving

 Highly infectious cases 

 Settings where transmission of M. tuberculosis is likely 

 Contacts at high risk for rapid development of TB disease if infected with 

M. tuberculosis

8.6 What is the infectious period?

The infectious period is the time during which a case is potentially capable of transmitting 

M. tuberculosis.

8.7 When does the infectious period end?

The infectious period ends when all of the following criteria are met: 

 Effective treatment 2 weeks or longer;

 Diminished symptoms (e.g., coughing less); and 

 Mycobacteriologic response (e.g., decrease in grade of sputum smear positivity).

8.8 What is the main goal of the TB case interview? 

The main goal of the interview with a TB case is to identify contacts who have been 

exposed to M. tuberculosis. 
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.9 List three strategies for conducting effective interviews.

 Have a clear understanding of the objectives of the interview.

 Plan the interview so that each objective is given adequate time.

 Ensure the interview takes place under conditions that protect the privacy 

of the case and encourage effective communication.

 Arrange for the assistance of an interpreter if you do not speak the same 

language as the case.

 Establish the foundation for an effective working relationship based on 

trust and respect. 

 Explain what a contact investigation is, how a contact investigation protects 

contacts from getting sick with TB disease, and what the case can do to help.

 Begin with an assessment of the case’s knowledge, feelings, and beliefs about TB.

 Remain objective, open-minded, and nonjudgmental.

 Ask open-ended questions and listen carefully to the case’s responses.

 Recognize and address the case’s fears and concerns about TB.

 Use opportunities that arise during the interview to educate the case about TB.

8.10 What is a proxy interview? Who may serve as an appropriate proxy?

Proxy interviews are interviews conducted with persons who are familiar with the case’s 

practices, habits, and behaviors. Potential proxies include family members, close friends, 

or other persons who know the case well. 

8.11 What two factors should be taken into account when determining the priority 

of each contact?

The priority assigned to each contact should be based on the following:

 Likelihood of transmission from the case 

 Contact’s risk for development of TB disease
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.12 In general, which contacts should be considered priority?

Priority should be given to contacts who

 Are exhibiting symptoms of TB disease

 Are at risk for rapid development of TB disease 

 Had repeated or extended exposure to the case 

 Were exposed to a case in an environment where transmission was likely, 

such as a small, crowded, or poorly ventilated room or vehicle

 Were exposed to a case undergoing medical procedures that can release 

substantial numbers of M. tuberculosis into the air

8.13 What are the four main functions of a field visit?

 Identify additional cases of TB disease

 Identify additional contacts 

 Gather additional information about environmental characteristics of places 

where exposure occurred

 Lay a foundation for additional contact investigation activities at those locations, 

if needed

8.14 List four safety precautions investigators should take while conducting field visits. 

 Wear an identification badge with a current photograph

 Work in pairs when visiting isolated or dangerous areas

 Have a working cell phone

 Limit visibility of valuable items

 Inform a coworker or supervisor of itinerary, planned route, and

expected time of return

 Practice appropriate infection control procedures

8.15 List five indicators of recent transmission.

 TB infection or TB disease in contacts younger than 5 years of age

 Change in contacts’ TST or IGRA status from negative to positive 

 A greater-than-expected rate of TB disease or TB infection among priority contacts 

 Evidence of secondary transmission

 TB disease among contacts not initially considered priority (particularly if 

genotypes match that of the case)
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.16 When can a contact investigation be concluded?

A contact investigation can be concluded if

 All contacts have been assessed for TB infection and disease

 Contacts with LTBI have completed or are close to completing treatment

 No additional secondary cases of TB are found, either among identified contacts 

or through reviewing genotype information

8.17 What is the purpose of evaluating the TB contact investigation?

Evaluating the TB contact investigation can help determine how effectively the contact 

investigation activities were conducted and identify areas that may be in need of 

improvement. 

Specifically, the purpose of evaluating contact investigation activities is to determine

 If the appropriate contacts were identified

 How many contacts were diagnosed with LTBI

 How many contacts with LTBI completed treatment 

 How many additional cases of TB disease were found 

 How many secondary cases of TB disease completed treatment

 How many contacts were not located

 How many contacts were located, but did not complete assessment 

 The timeliness of identifying and assessing contacts, and starting treatment 

if necessary

 If the contact investigation was performed in all necessary settings

 If the contact investigation was expanded appropriately
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.18 List the 10 steps of the systematic approach to contact investigation.

1. Review existing information about the case

2. Determine an initial estimate for the infectious period and estimate the 

degree of infectiousness

3. Interview the case

4. Review information and develop a plan for the investigation 

5. Refine the infectious period and degree of infectiousness 

6. Prioritize contacts

7. Conduct field visits 

8. Conduct contact assessments

9. Determine whether to expand or conclude an investigation

10. Evaluate the contact investigation activities 

8.19 What are the major activities of the contact assessment?

The major activities of the contact assessment include meeting with the contact and 

conducting a medical evaluation. During the meeting, the investigator should collect and 

confirm information and be sure to maintain the confidentiality of the case. Contacts 

should receive a medical evaluation that includes a medical history, HIV test, a TB 

symptom review, and a TST or IGRA to test for infection with M. tuberculosis.

8.20 What is the window period?

The window period is the time between the contact’s last exposure to the case and when 

a TST or IGRA can reliably detect infection.

8.21 What is window period prophylaxis? Which contacts should receive window period 

prophylaxis?

Window period prophylaxis is treatment for LTBI that is given to high-risk contacts 

(including children younger than 5 years of age, persons living with HIV, and other 

immunosuppressed persons) who have an initial negative test for TB infection less than 

8 to 10 weeks after their last exposure to the case.
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Module 8—Contact Investigations for Tuberculosis 

Answers to Study Questions, Continued

8.22 List five challenges associated with conducting contact investigations in 

congregate settings.

Challenges that are sometimes associated with conducting contact investigations in 

congregate settings include

 Large numbers of contacts

 Incomplete data for determining which contacts should be prioritized for 

assessment

 Difficulties related to maintaining confidentiality

 Incomplete information about contacts’ names and locating information

 A need to collaborate with officials and administrators who are not familiar with TB

 Media interest, particularly for investigations involving schools or worksites

 Political implications of negative publicity related to TB

 Legal implications for the facility 

8.23 What is a source case investigation?

A source case investigation is a method used to identify source cases. A source case is 

a person with TB disease who is responsible for transmitting M. tuberculosis to another 

person or persons. 

8.24 How can genotyping contribute to source case investigations?

TB genotyping can contribute to source case investigations by either confirming or 

disproving a named person as the source case. Additionally, genotyping can identify 

potential source cases that were not originally identified in the investigation.

Cases linked in the same chain of transmission should have matching genotypes. 

If the investigation yields no suspected source case, a review of all genotyping results 

from cases living in the same region as the case may identify a genotype match.
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers

8.1 You are a TB case manager at a busy clinic. Two new TB cases have been assigned to 

you. Indicate which case(s) require a contact investigation and note the reason why 

you made your decision.

Jose is a 35-year-old agricultural worker diagnosed with extrapulmonary TB of the 

kidneys. He lives with his wife in a small, rented house in a rural area. 

Dale is a 72-year-old widower who lives alone. He drives himself to the local 

retirement center for bingo and poker four times a week. He was recently evaluated 

for TB disease by his physician because he complained of having a cough, shortness 

of breath, fatigue, and weight loss. His sputum smears were positive and his culture 

results are pending. Dale’s chest x-ray shows a cavity in the right upper lobe of his 

lungs. The physician suspects TB and started Dale on a four-drug regimen.

Dale requires a contact investigation because he has cavitary TB disease and 

his sputum smears are positive. Jose does not require a contact investigation 

because he has extrapulmonary TB of the kidneys, which is not infectious. 
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.2 Calculate the infectious periods for the following TB cases:

Isaac is a 42-year-old man who was hospitalized on December 4th with symptoms 

of fever, night sweats, and cough. He was placed in airborne infection isolation for 

two weeks. On the same date (December 4th), AFB sputum smears were collected 

and were reported as positive with final cultures pending. Chest x-rays were taken on 

December 4th and reported as abnormal with cavitary disease. Isaac was diagnosed 

with suspected pulmonary TB with appropriate treatment started on December 5th. 

Isaac states that he started coughing around November 6th. His symptoms resolved on 

December 24th. Three consecutive sputum AFB smears were negative on February 10th.

The beginning of Isaac’s infectious period is August 6th (three months before 

the onset of symptoms). For contact investigation purposes, his infectious 

period ends on December 4th since he was effectively isolated and was no 

longer exposing any contacts. Biologically, the end of the infectious period 

would be February 10th because of the negative sputum smears, improved 

symptoms, and treatment for at least 2 weeks.

Trang is a 52-year-old woman who had a checkup on May 19th with her primary care 

provider. During this visit, she was found to have an abnormal chest x-ray. Sputum 

collected on the same day was reported as AFB smear positive with final cultures 

pending. On May 20th she was diagnosed with suspected pulmonary TB, started 

appropriate treatment, and was put on home isolation. Trang claims she never had 

a cough or other symptoms. Three consecutive induced sputum AFB smears were 

negative on June 15th, June 18th, and June 21st.

The beginning of Trang’s infectious period is February 19th (three months 

before the first finding consistent with TB). The end of her infectious period 

would be June 21st because she has three negative sputum smears and has 

been on treatment for at least 2 weeks.
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.3 You are the public health worker assigned to conduct a contact investigation for 

Judith, a 73-year-old woman who was recently diagnosed with infectious TB disease. 

Judith lives with her daughter in a small house outside of town. You are conducting 

the case interview in her home. 

What questions should you ask Judith during the interview to learn more 

about her contacts?

To identify Judith’s contacts, it is important to first determine her period of 

infectiousness. To estimate the start of the infectious period, you should ask 

Judith what symptoms she had (if any) and when they began. To determine 

the end of the infectious period, you should refer to her medical record.

Once the infectious period has been estimated, you should ask Judith about 

the following: 

 Where she spent time during her infectious period

 What activities or events she participated in during her infectious period

 Who she spent time with during her infectious period
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.4 Derrick is a 47-year-old man who has had a severe cough for about two months and 

started treatment for TB disease three days ago. He lives alone in a small apartment 

and works the night shift three times a week with two other employees at the 

convenience store a few blocks away from his home. During the day, Derrick goes to 

friends’ apartments nearby or stays in his apartment to watch TV. He often goes to 

the local bar in his neighborhood with his friends Reggie and Melvin. He usually eats 

at one of two restaurants—the Main Street Diner or Susie’s Kitchen.

Derrick says that his girlfriend, Tonya, spends the night with him a few times a week, 

and often brings her 2 year-old son Luke. Derrick also mentions another girlfriend, 

Kelly, who has stayed over about 10 times in the past three months. Last month, 

Derrick spent several days at Kelly’s house, where she lives with her mother.

Based on this information, who are Derrick’s contacts?

 Tonya and her son 

 Kelly and her mother 

 The two coworkers at the convenience store 

 Friends whom Derrick visits at home, and anyone else 

who lives in their house 

 Reggie, Melvin, and other persons who regularly 

go to the local bar with Derrick

 The bartender 

 Waiters, waitresses, or friends at the two restaurants 

Which contacts are at higher risk for TB infection and TB disease?

Tonya and her son are probably the most at risk because they frequently stay 

in Derrick’s apartment. Luke is especially at risk because he is younger than 

5 years of age. Kelly and her mother are also at risk because Derrick stayed 

at their house during the time he was probably infectious. In addition, the 

friends he spends the most time with—probably Reggie and Melvin—would 

be considered to be at higher risk. 
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.5 One week ago, Hector came to the health department complaining of night sweats, 

weight loss, and a cough that has lasted about a month. His sputum smears were 

positive and he started a four-drug regimen for TB disease.

When you interviewed Hector, you found out he lives with his 32-year-old wife, Mimi; 

his two sons, Luis, 2, and Javier, 4; and his mother-in-law, Alma, 65. Hector’s cousin, 

Henry, has stopped by the house a few times in the past month. 

Hector rides to work 5 days a week in a car with his friend Joe. The ride lasts 

about 30 minutes.

Hector works in a mail order packing warehouse. About 100 employees work in the 

main room with Hector, but the room is divided into several sections. There are 20 

persons in Hector’s section, and 4 of these persons are assigned to work closely with 

Hector. Hector eats lunch outside every day with these 4 coworkers.

About twice a week and on weekends, Hector goes to a small neighborhood bar 

located in the basement of a building. At the bar, Hector spends most of the time 

talking to the bartender. He notes that the bartender has been coughing a lot lately.

Based on this information, who are Hector’s contacts?

 Household members: Mimi, Luis, Javier, Alma 

 His friend Joe 

 His cousin Henry

 Four coworkers who work closely with Hector 

 The bartender at the local bar

Which contacts should be considered a priority?

All of the contacts listed above should be considered a priority. The highest 

priority should be given to the bartender because he is exhibiting symptoms 

of TB disease. Because of their young age, Luis and Javier are also at high risk 

and should be assessed as soon as possible. 
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.6 Carmen is a 30-year-old woman who was recently diagnosed with infectious 

TB disease. She works at the local community college and lives with her aunt.

A contact investigator from the local health department is conducting an interview 

with Carmen at Carmen’s home. Three coworkers and her aunt have been reported 

to be contacts by Carmen. 

Refer back to Figure 8.6 on page 45. Based on what is visible in the photo, is there 

evidence of any additional contacts in Carmen’s home other than her aunt?

The investigator should notice that there are photos of children and others 

who were not mentioned in the interview. In addition, the investigator should 

notice the toys and children’s shoes on the floor. There is also a pair of men’s 

shoes on the floor. Carmen has not mentioned other contacts in the house. 

However the photos, shoes, and toys suggest that there may be other persons 

who live in or visit the house. If additional contacts are identified, they should 

be considered for assessment. 
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.7 Priya is a 34-year-old woman who was diagnosed with infectious TB disease. 

As part of her contact investigation, you identified the following priority contacts: 

 Naveen (husband, 35 years old)

 Sanjay (son, 3 years old)

 Asha (close friend, 37 years old)

 Paul (co-worker, 52 years old)

 Marie (co-worker, 43 years old) 

Five weeks have passed since the contacts were last exposed to Priya while she 

was infectious. These contacts (a total of 5) have been assessed by the contact 

investigation team. None of the contacts were found to have TB symptoms. 

The TB skin test results were as follows:

 Naveen: 11 mm

 Sanjay: 0 mm

 Asha: 5 mm

 Paul: 3 mm

 Marie: 0 mm 

What follow-up testing and treatment are needed for contacts with 

a positive skin test?

Both contacts who have a positive TB skin test reaction, Naveen and Asha, 

should be given a chest x-ray to rule out the possibility of TB disease. If the 

chest x-ray is normal, they should complete a full course of treatment for 

LTBI. If the chest x-ray is abnormal, they should be evaluated for TB disease, 

including a sputum examination. 

Should any follow-up testing or treatment be given to contacts with

a negative skin test?

Yes. Because he is at high risk of rapidly developing TB disease if infected, 

Sanjay should start treatment for LTBI if his chest x-rays are normal and he 

has no TB symptoms. His last exposure to Priya while she was infectious 

occurred only 5 weeks ago; therefore, his skin-test result may be a falsenegative reaction. Sanjay should be given window period prophylaxis until 

8 to 10 weeks from his last exposure, when he should have a repeat skin 

test. If his chest x-rays are abnormal, he should be evaluated for TB disease, 

including a sputum examination.
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

Which contacts should receive a repeat skin test? When should the 

repeat test be performed?

Sanjay should be retested 8 to 10 weeks after he was last exposed to Priya. 

If Sanjay’s second skin test reaction is negative, he can stop taking treatment 

for LTBI. If his second skin test reaction is positive, Sanjay should complete 

a full course of treatment for LTBI. 

The other contacts who had a negative skin test reaction, Paul and Marie, 

should be retested 8 to 10 weeks after they were last exposed to Priya while 

she was still infectious. Anyone who has a positive reaction to the second skin 

test should complete a full course of treatment for LTBI after TB disease has 

been ruled out. 
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Module 8—Contact Investigations for Tuberculosis 

Case Study Answers, Continued

8.8 Jung is a 3-year-old child who has been diagnosed with TB meningitis. Jung, his 

parents, and his paternal grandmother immigrated to the United States from China 

one year ago. 

Should a source case investigation be conducted?

Yes, a source case investigation should be conducted to locate the person 

who transmitted TB to Jung. When a child has TB infection or disease, it 

indicates that TB was transmitted relatively recently. In Jung’s case, his young 

age indicates that he must have been exposed to someone with TB disease 

during the past 3 years. The person who is the source of this exposure is 

called the source case. In this situation, the source case may be a family 

member or friend (in the United States or in China) with infectious, possibly 

untreated, TB disease. 

What would be the purpose of conducting a source case investigation for Jung?

The purpose of a source case investigation would be to determine 

 Who transmitted M. tuberculosis to Jung 

 Whether the source case is still infectious

 Whether the source case was reported to the health department 

 Whether any other persons were infected by the source case

 The drug susceptibility test results and genotyping results of the source case 

who transmitted TB to Jung
Module 8—Contact Investigations for Tuberculosis 

99

Self-S

8

tudy Modules onTuberculosis 

Module

Appendix For Accessibility

Figure 8.1: This figure is titled Infectious Period Estimate for 

a Smear Positive Case with TB Symptoms. The figure is an 

example of determining an initial estimate for the beginning and 

end of the infectious period for a case with a positive sputum 

smear result and symptoms of TB disease. In this example 

timeline, the infectious period begins on August 1. Symptoms 

start on November 1. Treatment starts on November 15. The 

case had negative sputum smears, no symptoms, and treatment 

for 2 weeks or longer by December 1st. Therefore, the end of 

the infectious period would be December 1st. 

Figure 8.2: This figure is titled Infectious Period Estimate for 

a Smear Negative Case without TB Symptoms and No Cavities 

on Chest X-Ray. This figure shows how the infectious period 

is estimated as one month before a healthcare provider first 

suspects TB. On this timeline, the infectious period begins on 

August 15. The case was isolated on September 15th, the same 

date that TB was first suspected. Therefore, the end of the 

infectious period would be September 15th.

Figure 8.4: An example of a TB interview checklist that can 

be used during a case interview. By following the checklist, the 

contact investigator is guided to explain contact investigation, 

gather information on potential contacts, and answer questions.

Figure 8.5: This figure is titled Refined Infectious Period 

Estimate for a Smear Positive Case with TB Symptoms. The 

figure shows the refined infectious period for the case presented 

in Figure 8.1. In this timeline, the infectious period started on 

June 1, 3 months before symptom onset. Symptoms started 

on September 1. Treatment started on November 15. The case 

had negative sputum smears, no symptoms, and treatment for 

2 weeks or longer by December 1st. Therefore, the end of the 

infectious period would be December 1st.
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Module 8—Contact Investigations for Tuberculosis 

Figure 8.7: An example of how to determine the prevalence of 

newly diagnosed infection with M. tuberculosis among contacts.

 Eleven contacts were identified for a reported TB case. One 

contact had a documented previous positive TST result. The 

other 10 contacts did not have documented previous TST 

results. These 10 contacts had a skin test administered; seven 

had positive TST results and three had negative TST results. 

 Step one: Determine the total number of contacts who 

completed testing for M. tuberculosis infection. Do not 

include contacts who have a documented previous positive 

test result, have not completed testing, or who were not 

tested. 

 For this example, 10 contacts completed testing. 

 Step two: Determine the number of contacts with a newly 

positive TST result. 

 For this example, 7 of the 10 contacts who were tested 

had a positive TST result.

 Step three: Divide the number of contacts with a newly 

positive test result by the total number of contacts that 

completed testing. 

 For this example, 7 is divided by 10 which equals 0.70. 

 Step four: Multiply the number from Step 3 by 100%. 

 For this example, 0.70 is multiplied by 100% which 

equals 70%. 

 Answer: The TB infection prevalence for the contacts is 70%. 

Figure 8.8: This figure is titled Calculation of the Window 

Period. The figure shows an example of calculating the window 

period and determining when a repeat test should occur for 

contacts with an initial negative test result. The window period 

is the time between the contact’s last exposure to the case and 

when a TST or IGRA can reliably detect infection, usually 8 to 

10 weeks later. 

In this timeline, the contact’s last exposure to the case is on July 

1. An initial TST or IGRA is negative 4 weeks later on August 

1st. The contact should have a repeat test 8 to 10 weeks after 

last exposure. Therefore, the contact should have a repeat TST 

or IGRA between September 1 and September 15. 

Figure 8.9: A complex flow chart that diagrams the assessment 

and management process of TB contacts. The management and 

assessment of TB contacts is further explained in the Assessment 

and Management of TB Contacts section in Module 8.
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Module 8—Contact Investigations for Tuberculosis 

Notes
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Module 8—Contact Investigations for Tuberculosis 

Notes

CS329840-A Publication Number 99-6206