9

Module

Self-Study Modules on Tuberculosis

Tuberculosis 

Outbreak Detection 

and Response

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

Division of Tuberculosis Elimination

Tuberculosis Outbreak 

Detection and Response

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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on Tuberculosis 

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Contents

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

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

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

Introduction to TB Outbreak Detection and Response . . . . . . 4

Systematic Approach to TB Outbreak Response . . . . . . . . . . . 12

Special Circumstances in TB Outbreak 

Detection and Response . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

Additional Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

Answers to Study Questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Case Study Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

Appendix For Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

Module 9—Tuberculosis Outbreak Detection and Response 

v

Background

Detecting and responding to TB outbreaks are among the important challenges public health 

programs face today in eliminating TB. Delays in detecting TB cases, and delayed or incomplete 

contact investigations, can lead to TB outbreaks.

Despite many similarities between contact investigations and outbreaks in how public health 

programs manage cases and contacts, the overall response needed for outbreaks is much more 

complex. Health departments may find it difficult to respond quickly and effectively to TB 

outbreaks.

The techniques used to detect and respond to TB outbreaks are guided by knowledge of 

the transmission and pathogenesis of M. tuberculosis and by the principles of effective 

contact investigations. Thus, in order to understand how to detect and respond effectively 

to a TB outbreak, it is important to have a good understanding of these concepts, which are 

presented in Module 1, Transmission and Pathogenesis of Tuberculosis and Module 8, Contact 

Investigations for Tuberculosis.

Objectives

After working through this module, 

you will be able to 

1. List the criteria to meet the 

definition of a TB outbreak.

2. Describe three methods of TB 

outbreak detection.

3. Describe the role of 

genotyping in TB outbreak 

detection and investigation.

4. List the ten steps of the 

systematic approach to TB 

outbreak response. 

define

explain

describe

list

Module 9—Tuberculosis Outbreak Detection and Response 

1
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.

chain of transmission—often used to 

describe the circumstances and timing of 

transmission from a source case to one 

or more persons who develop TB disease 

(secondary cases). A chain of transmission 

can extend over a few months, years, or 

decades. Cases involved in the same chain 

of transmission almost always have matching 

genotypes (when this information is available).

descriptive epidemiology—the aspect of 

epidemiology concerned with organizing and 

summarizing health-related data according to 

person, place, and time

epidemic curve (epi curve)—a graph that 

displays the number of TB cases and when 

they were identified. Time is plotted on the 

horizontal x-axis and the number of cases is 

plotted on the vertical y-axis.

epidemiologic link (epi link)—

characteristic(s) TB patients share that 

explains where and when TB could have 

been transmitted between them 

genotype—distinct genetic pattern of an 

organism

genotype cluster—when two or more cases 

have matching genotypes

genotyping—a laboratory-based method 

that can determine the genetic pattern of 

the strain of M. tuberculosis that caused TB 

disease in a person

outbreak case definition—a standard set of 

criteria for deciding which TB cases could be 

involved in an outbreak

2
outbreak hypotheses—theories about how, 

when, and where TB transmission may have 

occurred during an outbreak

outbreak line list—summary of the cases that 

meet the outbreak case definition

recent transmission— transmission of TB that 

has occurred in the recent past, as opposed to 

reactivation of latent TB infection. Although the 

precise time period is not well defined, “recent” 

transmission is often considered to be within 

the last 2 years.

secondary case—an instance of TB after a 

known exposure, usually related to the index 

case in an investigation

spot map—a technique for showing where 

cases may have been exposed to TB or where 

they may have exposed others after developing 

TB disease

TB case surveillance—monitoring the 

occurrence of TB disease in specific geographic 

areas, populations, and time periods

TB Genotyping Information Management 

System (TB GIMS)— a secure CDC-sponsored 

online national database of M. tuberculosis

genotyping and TB case information

TB outbreak—when there are more TB cases 

than expected within a geographic area or 

population during a particular time period, and 

there is evidence of recent transmission of M. 

tuberculosis among those cases

TB outbreak response—a process used by 

public health programs to investigate and 

intervene when a TB outbreak is suspected or 

confirmed

TB outbreak response plan—an action plan 

that helps guide outbreak response

Module 9—Tuberculosis Outbreak Detection and Response 

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Introduction to TB Outbreak 

Detection and Response

What is a TB Outbreak?

Definitions for TB outbreaks are relative to the local context. 

However, a TB outbreak is generally defined as a situation 

where there are

 More TB cases than expected within a geographic area or 

population during a particular time period, AND

 Evidence of recent transmission of M. tuberculosis among 

those cases

Although the time period is not well defined, recent 

transmission generally refers to a situation where TB 

transmission occurred within the previous 2-year period. This 

implies that cases involved in an outbreak have been exposed 

and infected with M. tuberculosis in the past 2 years, as opposed 

to having developed active TB disease from latent TB infection 

caused by exposure from a long time ago. Because an outbreak 

indicates that there is the potential for extensive transmission of 

M. tuberculosis, a TB outbreak should always be considered a 

public health emergency.

What is TB Outbreak Response?

TB outbreak response is a process used by public health 

programs to investigate and intervene when a TB outbreak 

is suspected or confirmed. The ultimate goal of TB outbreak 

response is to interrupt ongoing transmission of M. tuberculosis. 

An outbreak generally involves multiple TB cases with several 

overlapping contacts. Compared to TB contact investigations, 

responding to TB outbreaks requires many more resources, a 

larger and more diverse group of partners and stakeholders, and 

more extensive collaboration and communication.

An outbreak generally 

involves multiple TB 

cases with several 

overlapping contacts.

A TB outbreak is generally 

defined as a situation 

where there are more 

TB cases than expected 

within a geographic area 

or population during a 

particular time period, 

and there is evidence 

of recent transmission 

of M. tuberculosis

among those cases.

Module 9—Tuberculosis Outbreak Detection and Response 

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Who is Responsible for Detecting and Responding 

to TB Outbreaks? 

In the United States, state and local health departments have 

legal responsibility for the prevention and control of TB in 

their communities. This means health departments are legally 

responsible for ensuring appropriate response to TB outbreaks 

in their jurisdictions. However, because TB outbreak response 

typically requires substantial resources, it may be difficult for 

local health departments to independently manage TB outbreaks 

while maintaining adequate staffing and coverage for other 

public health activities. A quick and effective response to TB 

outbreaks can be a challenge for TB control programs even with 

substantial experience and resources. Thus, health departments 

should consider requesting assistance from other agencies, such 

as neighboring local health departments or the state health 

department, to help with the outbreak response.

The Centers for Disease Control and Prevention (CDC) can also 

assist with TB outbreak response at the request of the state 

health department, another federal agency, or a sovereign entity 

such as an American Indian tribe or a U.S. territory.

What is TB Outbreak Preparedness?

TB programs can improve their ability to respond to outbreaks 

by planning in advance how they will respond when an 

outbreak happens. This is sometimes called TB outbreak 

preparedness. Outbreak preparedness typically involves

 Determining what is considered to be a potential TB 

outbreak (i.e., defining what events require further attention 

and action) 

 Discussing who should be a part of the TB outbreak 

response team, including staff from other areas of the health 

department for whom TB is not part of their normal duties 

(e.g., STD or HIV program staff)

 Developing mechanisms for ensuring resources can be 

accessed quickly and then used as efficiently and effectively 

as possible

 Supporting collaboration and communication among 

everyone involved 

 Ensuring that staff are educated about proper infection 

control procedures

A quick and effective 

response to TB outbreaks 

can be a challenge for 

TB control programs 

even with substantial 

experience and resources.

TB programs can improve 

their ability to respond 

to outbreaks by planning 

in advance how they 

will respond when an 

outbreak happens.

Module 9—Tuberculosis Outbreak Detection and Response 

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How is TB Outbreak Preparedness Done?

There are many benefits to preparing in advance for TB 

outbreaks. Outbreak preparedness helps give health department 

staff and others involved with TB outbreaks general direction 

about when and how outbreak response efforts should happen. 

Even without knowing the specifics of an outbreak, some 

planning can almost always be done in advance. Because 

circumstances and capacities of public health programs vary, 

so do their approaches to outbreak preparedness. Creating an 

initial action plan, also called a standing outbreak response 

plan, can help guide first steps once an outbreak is suspected.

Planning the more predictable aspects of an outbreak in 

advance will allow for more time to be spent on responding 

to the outbreak itself. For example, points of contact at partner 

agencies and sources of additional resources can be identified 

ahead of time. 

Part of being prepared is creating a framework for requesting 

assistance from other agencies. Creating preexisting agreements 

with these partner agencies is one option. 

A customizable template of a standing outbreak response 

plan can be accessed online at http://www.currytbcenter.ucsf.

edu/products/view/model-tuberculosis-outbreak-response-plantemplate-low-incidence-areas. 

Standing outbreak response plans cannot predict the particular 

issues surrounding an outbreak. Plans will need to be revised 

based on the circumstances of each outbreak.

How are TB Outbreaks Detected?

Timely detection of TB outbreaks is a fundamental component 

of TB prevention and control. Detecting signs that suggest 

an outbreak may be occurring is important because a rapid 

response can help control and minimize outbreaks.

Outbreaks can be detected through the following activities:

 Observations from health department staff and others in the 

community

 TB contact investigations

 TB case surveillance

 TB genotype surveillance

During these activities, health department workers should be 

alert for signs of more TB cases than expected and evidence of 

recent transmission among those cases.

Creating an initial 

action plan, also called 

a standing outbreak 

response plan, can help 

guide first steps once an 

outbreak is suspected.

Health department workers 

should be alert for signs 

of more TB cases than 

expected and evidence 

of recent transmission 

among those cases.

Module 9—Tuberculosis Outbreak Detection and Response 

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Observations from Health Department Staff and Others in 

the Community

TB outbreaks are sometimes first detected through astute 

observations from frontline staff at the health department. 

For example, an outreach worker may notice that he or she 

is performing more directly observed therapy (DOT) visits 

than usual to a particular neighborhood. Or a public health 

nurse may notice there are more homeless cases than usual. 

Observations like these always call for further investigation to 

determine if the cases are connected. 

TB outbreaks can also come to the attention of health 

departments when other health care providers or members 

of the public report a concern. Such reports should be taken 

seriously and investigated by the health department. Even in 

an area where the overall TB case numbers are declining, an 

outbreak could be occurring. 

TB Contact Investigations

Some contact investigation findings are evidence of recent 

transmission, which can indicate a potential TB outbreak. 

For example 

 TB infection or TB disease in contacts younger than 5 years 

of age

 Change in contacts’ tuberculin skin test (TST) or interferongamma release assay (IGRA) status from negative to positive 

 More than expected TB disease or TB infection among 

contacts 

 TB disease among contacts not considered priority 

 Any evidence of secondary transmission

Someone in the health department, such as the TB program 

manager, should have the responsibility to routinely review 

contact investigation results, actively looking for evidence that 

an outbreak might be occurring. For more information on TB 

contact investigations, refer to Module 8, Contact Investigations 

for Tuberculosis.

TB Case Surveillance 

Public health programs should monitor the occurrence of TB 

disease in specific geographic areas, populations, and time 

periods. This is known as TB case surveillance. 

An unexpected increase in the number of TB cases or an 

increase in the TB case rate within a geographic area or 

population can be one of the first signs of an outbreak. 

Module 9—Tuberculosis Outbreak Detection and Response 

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Similarities in case demographics, TB risk factors, and TB drug 

resistance patterns may also be early signs of an outbreak. In 

areas with a low incidence of TB, outbreaks are more often 

easily detected through TB case surveillance.

It is important to note that an increase in the number of TB 

cases does not always indicate that an outbreak is occurring. 

An increase in TB cases can happen for reasons other than 

an outbreak. Such scenarios are sometimes called “pseudooutbreaks.” Circumstances that can lead to pseudo-outbreaks 

are listed in Table 9.1.

An increase in the number 

of TB cases does not 

always indicate that an 

outbreak is occurring. 

An increase in TB cases 

can happen for reasons 

other than an outbreak.

Table 9.1—Situations Where an Increase in the Number of TB Cases is Not an Outbreak 

When an Increase in TB Cases May NOT be an Outbreak

An increase in TB cases can happen for reasons other than an outbreak. Such scenarios are sometimes called 

“pseudo-outbreaks.” Circumstances that can lead to pseudo-outbreaks include

 An influx of persons from areas where TB is common (e.g., refugees)

 Persons are misdiagnosed with TB, as a result of mislabeling or contamination during specimen collection or in the 

laboratory (sometimes called false-positive laboratory results)

 Improved TB screening, diagnostic procedures, or reporting of cases (i.e., better case detection)

 A new clinician in a jurisdiction who is more likely than predecessors to diagnose clinical TB

TB Genotype Surveillance

TB genotype surveillance is another way that public health 

programs can detect outbreaks. This method may be 

particularly helpful in areas with a high incidence of TB 

disease. 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. TB genotype results can help 

confirm, disprove, or detect connections among cases. Cases 

involved in the same chain of transmission almost always have 

matching genotypes.

A genotype cluster could be the first sign that an outbreak is 

happening. A genotype cluster is when two or more cases have 

matching genotypes. However, not all genotype clusters are 

outbreaks. Genotype clusters can be caused by circumstances 

other than outbreaks, such as laboratory mislabeling, 

Module 9—Tuberculosis Outbreak Detection and Response 

8
contamination, or presence of what has been termed a 

common genotype (i.e., a genotype that is common in a certain 

geographic area or population that is not necessarily related to 

recent transmission). 

In the United States, genotyping information on individual TB 

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 TB case information. TB GIMS has an 

automatic function (called “cluster alerts”) that notifies TB GIMS 

users of genotype clusters that may require further investigation. 

Not all genotype clusters or TB GIMS cluster alerts represent 

outbreaks. When genotype clusters are found, additional 

investigation is needed.

The following findings from genotype surveillance may suggest 

an outbreak and require further investigation:

 A genotype cluster is seen in only one jurisdiction or a 

small number of jurisdictions

 A growing number of cases have a new or uncommon 

genotype 

 An unexpected increase in cases with a common genotype 

is observed

 New cases with a TB genotype associated with a prior TB 

outbreak are identified

 Cases with the same genotype and another factor in 

common, such as homelessness, incarceration, or substance 

abuse, are identified

Applications of TB genotyping for outbreak detection and 

response are discussed throughout this module. For more 

information, refer to the CDC’s Best Practices for GenotypingBased Tuberculosis Outbreak Detection (www.cdc.gov/tb/

publications/factsheets/statistics/Genotyping_BestPractices.pdf).

A genotype cluster could 

be the first sign that an 

outbreak is happening.

Module 9—Tuberculosis Outbreak Detection and Response 

9
Study Questions 9.1–9

9.1 What is a TB outbreak?

9.2 What is TB outbreak response?

9.3 What are three methods that health departments can use to detect TB outbreaks? 

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

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Study Questions 9.4–9

9.4 List four circumstances when an increase in the number of TB cases may not 

represent an outbreak.

9.5 What is a genotype cluster?

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

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Systematic Approach to TB 

Outbreak Response

Public health programs can respond more quickly and more 

effectively to potential TB outbreaks by using a systematic 

approach. Although the order and timing of TB outbreak 

response activities will vary, the overall response generally 

includes the following 10 steps:

1. Confirm the existence of an outbreak

2. Define and list outbreak cases 

3. Examine existing information about outbreak cases

4. Convene the outbreak response team and develop the 

outbreak hypotheses 

5. Fill information gaps

6. Implement the specific outbreak response plan

7. Communicate interim findings

8. Summarize the outbreak response

9. Implement recommendations

10. Evaluate the outbreak response 

This section of the module will describe each of the steps 

listed above.

Step 1: Confirm the Existence of an Outbreak

When a TB outbreak is suspected, investigation is needed to 

confirm that an outbreak is actually occurring before mounting 

a full outbreak response. To confirm an outbreak, investigators 

need to determine whether there are both

 More cases than expected within a geographic area or 

population during a particular time period, AND

 Evidence of recent transmission of M. tuberculosis among 

those cases.

When a TB outbreak is 

suspected, investigation 

is needed to confirm that 

an outbreak is actually 

occurring before mounting 

a full outbreak response.

Module 9—Tuberculosis Outbreak Detection and Response 

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More Cases than Expected

An important first step when determining whether there are 

more cases than expected is to verify the reported cases actually 

have TB disease. Determining if reported cases actually have 

TB disease typically requires reviewing clinical findings and 

laboratory results for each case.

When clinical findings for cases are not consistent with the 

laboratory results, further efforts are usually needed to confirm 

these persons have TB disease. For example, when a person 

without any signs or symptoms of TB disease is reported as a 

case based on a single positive TB culture, it is important to 

investigate whether the laboratory result is accurate. 

Evidence of Recent Transmission Among Cases

When an unexpected increase in cases is confirmed or a growing 

genotype cluster is identified, investigators need to look for 

evidence of recent transmission among the cases to determine if 

there is an outbreak. This typically begins with reviewing available 

information about the cases, such as contact rosters and medical 

records. Investigators may also confer with program staff who are 

familiar with the cases. In some situations, additional information 

will need to be gathered through re-interviewing cases and 

conducting field visits.

One way to assess if cases are involved in a chain of recent 

transmission is to look for characteristics that the cases have in 

common. This is because TB outbreaks generally involve persons 

with similar demographic characteristics and TB risk factors. For 

example, cases may share characteristics such as homelessness, 

previous incarceration, or substance use. 

In addition, investigators should look for epidemiologic links 

(epi links) among cases. An epi link is a characteristic that TB 

cases share that explains where and when TB could have been 

transmitted between them. For example, cases have an epi link if 

they named each other as contacts or shared airspace at the same 

location (e.g., workplace, bar, shelter) at the same time. However, 

sometimes the epi links are not as evident, such as when cases are 

in the same social circles (but do not identify each other by name) 

or they spend time at the same place (but cannot be certain they 

were there together at the same time).

An important first step 

when determining 

whether there are more 

cases than expected is to 

verify the reported cases 

actually have TB disease.

When an unexpected 

increase in cases is 

confirmed or a growing 

genotype cluster is 

identified, investigators 

need to look for evidence of 

recent transmission among 

the cases to determine 

if there is an outbreak.

Investigators should look 

for epidemiologic links 

(epi links) among cases. An 

epi link is a characteristic 

that TB cases share that 

explains where and 

when TB could have been 

transmitted between them.

Module 9—Tuberculosis Outbreak Detection and Response 

13
Some initial questions investigators can use while reviewing 

information to help determine if cases may be linked in a chain of 

recent transmission include 

 Have any of the cases named each other as contacts?

 Do any of the cases have contacts in common?

 Do any of the cases have similar TB risk factors?

 Do the cases live or work near each other?

Genotyping information can be used to confirm epi links and 

may also identify previously unknown epi links. Investigators 

should review information to see if genotype-matched cases 

have risk factors in common, such as having spent time at the 

same homeless shelter or jail.

In some situations, genotyping information may not be 

available. These situations include

 Clinical cases (no culture available)

 Culture-negative cases

 Cases whose culture results are still pending

In such situations, if epi links among cases can be reasonably 

established, it is usually advisable for public health programs to 

proceed as though there is an outbreak once it is confirmed that 

the cases actually have TB disease.

Genotyping information 

can be used to confirm 

epi links and may also 

identify previously 

unknown epi links.

Module 9—Tuberculosis Outbreak Detection and Response 

14
Case Study 9.

Colin is an 8 month old child who was diagnosed with TB disease in Brown County. Typically, 

Brown County has less than two TB cases per year. The health department did a source case 

investigation and found that his mother, Kate, has latent TB infection and his Uncle Dave 

has TB disease. 

As an infant, Colin is unable to produce sputum, so the health department does not have a 

culture to submit for genotyping. However, the health department receives the results of Dave’s 

TB genotype and finds that it matches with two other recent cases from Brown County. 

Would this lead you to suspect a potential TB outbreak? Why or why not?

Answers to case studies are on pages 64– 66

Module 9—Tuberculosis Outbreak Detection and Response 

15
Step 2: Define and List Outbreak Cases 

When the information gathered in Step 1 suggests an outbreak 

is occurring, the next step is to determine 

 A consistent way to define which cases may be part of the 

outbreak (the outbreak case definition)

 An efficient way to summarize those cases (the outbreak 

line list)

TB Outbreak Case Definition

TB outbreak case definitions are a standard set of criteria for 

deciding which TB cases could be involved in the outbreak. 

Knowing which TB cases to investigate helps to estimate the 

size of the outbreak and determine what resources will be 

needed for the response.

TB outbreak case definitions usually include the following four 

components:

1. TB genotype information (if available)

2. Characteristics about the affected persons (person)

3. Information about the location or place (place)

4. Time during which the outbreak occurred (time)

1. TB Genotype Information

For culture-confirmed cases, genotyping information is an 

important component of TB outbreak case definitions. This 

is because cases involved in the same chain of transmission 

almost always have matching genotypes (when this 

information is available). Cases with genotypes that are 

different than the outbreak genotype are unlikely to be 

part of the outbreak and can usually be excluded from the 

investigation. (Note: when genotyping information is not 

available, it is usually advisable to include cases as part of 

the outbreak if epi links can be established.)

2. Person

Person usually describes what the cases have in common 

that led investigators to suspect they may be involved in 

the same chain of recent transmission, such as similar 

demographic characteristics. For example, the outbreak 

may primarily involve homeless persons. This information is 

particularly helpful in situations where the TB genotype is 

not available for all cases. 

TB outbreak case 

definitions are a standard 

set of criteria for deciding 

which TB cases could be 

involved in the outbreak.

TB outbreak case 

definitions usually include 

TB genotype information, 

characteristics about 

the affected person, 

information about the 

location or place, and 

the time during which 

the outbreak occurred.

Module 9—Tuberculosis Outbreak Detection and Response 

16
3. Place

Place describes the geographic boundaries of the outbreak. 

Typically place refers to a city, county, or state, but it can be 

as narrow as a specific site, such as a nursing home. 

4. Time

The time frame used in a TB outbreak case definition 

usually begins at the start of the infectious period for the 

person suspected of being the initial source case and ends 

at the present time. 

However, for outbreaks that extend over several years, it 

may not be practical to use the start of the infectious period 

for the initial source case. To keep the number of cases 

manageable, investigators may choose to focus on the two 

to three most recent years, because contacts of the more 

recent cases are most likely to benefit from interventions 

such as treatment for LTBI. To review information on 

calculating infectious periods, refer to Module 8, Contact 

Investigations for Tuberculosis.

Connecting cases to an outbreak usually requires that they 

be epi-linked to other cases in the outbreak, particularly if 

genotyping information is not available. 

It is very important to apply the outbreak case definition in 

the same way to all cases being considered for inclusion in 

the investigation. However, outbreak case definitions can be 

modified as investigators learn new information about how 

transmission is occurring. For example, an initial case definition 

could include all cases with a specific TB genotype and 

established social connections and any other epi-linked cases 

that do not have genotyping information available. Depending 

on the situation, an epi link could be defined very strictly 

(e.g., cases identify one another by name) or more inclusively 

(e.g., any history of homelessness).

As more information is learned, the epi link definition can 

become more specific (e.g., cases stayed at a particular shelter). 

If more jurisdictions join the investigation, the geographic 

boundaries of the outbreak case definition can expand 

accordingly. 

Determining which cases are involved in an outbreak is a 

process that can take some time to complete. Because of this, 

investigators will often use terms such as “definite,” “probable,” 

and “possible” to distinguish among or classify cases while 

waiting for genotyping results and working on epi link 

information. Examples of this practice are shown in Table 9.2. 

It is very important to 

apply the outbreak case 

definition in the same 

way to all cases being 

considered for inclusion 

in the investigation.

Module 9—Tuberculosis Outbreak Detection and Response 

17
Table 9.2—Classifying Outbreak Cases Based on Epi Links and TB Genotype Information*

Case Description Epi Links to Other Cases 

in the Outbreak? TB Genotype Information

Definite Outbreak Case Yes Genotype matches outbreak strain

Probable Outbreak Case Yes Genotype unknown or pending

Possible Outbreak Case Investigation of epi links 

is pending Genotype matches or no genotype available

Not an Outbreak Case Yes, no, or unknown Genotype is substantially different from outbreak strain

*It is important to note that some TB programs may classify outbreak cases differently.

Outbreak Line List

An outbreak line list is a summary of the cases that meet the 

outbreak case definition. 

The line list is one of the most useful tools during an outbreak 

investigation, as it allows investigators to quickly see key 

information about every case. The line list should be considered 

a confidential document and protected from unauthorized 

disclosure.

In a line list, each row represents a different case. Each column 

contains key information on every case such as

 Identifying Information

Each case in the line list should have an identifier listed. If 

the line list is going to be shared externally with persons 

who do not have a need to know the identities of the cases, 

identifiers other than names or initials should be used to 

protect confidentiality. For example, the first case might be 

labeled “Case 1,” the second “Case 2,” and so forth. These 

are also useful shorthand labels when making epi curves, 

plotting infectious periods, and creating spot maps and 

diagrams (for more information, refer to Step 3 on page 23).

 Demographic Information

The demographic information columns provide details 

needed to characterize the cases in an outbreak, such 

as age, gender, race/ethnicity, and occupation. Using 

a separate column for each characteristic may make it 

easier to calculate the number of cases with particular 

characteristics.

An outbreak line list is 

a summary of the cases 

that meet the outbreak 

case definition.

Module 9—Tuberculosis Outbreak Detection and Response 

18
 Risk Factor Information

Including information about risk factors such as recent 

incarceration or homelessness on the line list is another way 

to characterize the cases. This can help investigators tailor 

their activities to make the investigation more effective. 

 Clinical and Laboratory Information

Clinical and laboratory information helps to summarize 

the level of infectiousness for each case. Information could 

include the site and severity of TB disease (e.g., sputum 

smear and chest x-ray results) and, where applicable, 

infectious periods. 

Other relevant information should be included in a final 

“comments” column.

Using a simple format for the line list is best. Line lists can 

initially be created informally using white boards or flip charts 

(Figure 9.1), but then should be transferred into and regularly 

updated using software programs such as Microsoft Excel. The 

number and types of columns in a line list can be changed as 

needed. An example of a simple line list for a TB outbreak is 

shown in Table 9.3.

Each column of the line list 

contains key information 

on every case, such as 

identifying information, 

demographic information, 

risk factor information, 

and clinical and 

laboratory information.

Figure 9.1—Outbreak investigators compiling information on white board.

Module 9—Tuberculosis Outbreak Detection and Response 

19
Table 9.3—Example Line List for TB Outbreak Investigation

Identifier Case 

Description Age Gender Risk Factor Clinical Information Genotype

Case 1 Definite 

outbreak case 55 M

Homeless, 

recently 

incarcerated

Pulmonary, smear 

positive G12345

Case 2 Possible 

outbreak case 30 M Homeless, foreign born

Pulmonary TB, smear 

positive G12345

Case 3 Probable 

outbreak case 3 M

Young age, recent 

contact to an 

outbreak case

Culture negative, 

responding to 

treatment

Unknown 

(culture 

negative)

Case 4 Definite 

outbreak case 20 M HIV, substance abuse

Pulmonary, smear 

negative G12345

Investigators should work together to create and update the 

line list. This ensures everyone is familiar with the outbreak 

case definition and current cases. The process of creating and 

regularly reviewing the line list together also helps investigators 

pool their collective knowledge about cases, recognize patterns, 

and discuss the information gaps. Regardless of how the 

line list is created or maintained, it is important for everyone 

on the outbreak response team to have access to the most 

current version, as it will be updated frequently throughout the 

outbreak response.

Module 9—Tuberculosis Outbreak Detection and Response 

20
Study Question 9.6–9

9.6 What information is typically included in an outbreak case definition? 

9.7 What is an outbreak line list?

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

21
Case Study 9.

You are a health care worker at the local health department and have been assigned to 

investigate a TB outbreak. The TB genotype associated with this outbreak is G12345.

Using the line list below, determine if each case is a definite, probable, possible, or not an 

outbreak case. 

Case ID Age Gender Genotype Epi Linked to Other 

Outbreak Cases? Answer

TB291 35 M G12345 Yes

TB302 75 F G98765 No

TB304 32 F Unknown Yes

TB309 35 M G12345 Pending

TB310 40 M G12345 Yes

Answers to case studies are on pages 64– 66

Module 9—Tuberculosis Outbreak Detection and Response 

22
Step 3: Examine Existing Information about 

Outbreak Cases

The line list developed in Step 2 begins the process of 

examining information about the outbreak cases in a structured 

way. Examining information about the outbreak cases helps 

investigators develop the outbreak hypotheses (i.e., theories 

about how, when, and where transmission may have happened). 

Outbreak hypotheses are discussed more in Step 4.

During Step 3, investigators should compile

 Information about the outbreak cases 

 Contact investigation results for each of the outbreak cases

Compiling Information about Outbreak Cases

Compiling information for each case can help investigators 

recognize overlaps in cases’ residences, relationships, or 

activities, as well as identify locations and times where 

transmission may have occurred.

Descriptive Epidemiology

Similarities among cases from the line list can be examined 

more closely with descriptive epidemiology. Descriptive 

epidemiology characterizes outbreaks by 

 Person

 Place

 Time

Characterizing Outbreaks by Person

One way to characterize outbreaks by person is to determine 

the proportion of cases that share a particular characteristic. 

This is referred to as the frequency of a characteristic. Examples 

of characterizing by person may include homelessness or 

incarceration. 

It is important to ensure that all cases have been assessed 

for each characteristic. If not, then the frequency of that 

characteristic may be underestimated. For example, the HIV 

infection status of each case must be known to calculate an 

accurate proportion of cases with HIV infection. 

Another challenge is to make sure that all investigators are 

defining risk factors in the same way. Homelessness, for 

example, needs to be consistently defined (e.g., not just shelter 

use, but also “couch surfing”).

Descriptive epidemiology 

characterizes outbreaks by 

person, place, and time.

Module 9—Tuberculosis Outbreak Detection and Response 

23
Some characteristics investigators can use to characterize TB 

outbreak cases by person include

 U.S.-born

 Foreign-born

 Age younger than 5 years

 HIV-infected

 Diabetic

 Excess alcohol use

 Illicit drug use

 Homeless

 Recent incarceration

 AFB smear-positive

 Cavitary TB disease

Characterizing Outbreaks by Place

Place can have different meanings depending on the 

circumstances of the outbreak. For example, it might refer to 

the city or state in which cases reside. More specific meanings 

include where cases sleep, work, volunteer, attend school, and 

where they spend their leisure time. 

Spot maps and diagrams can be extremely helpful for 

identifying locations where cases may have been exposed to 

TB or where they may have exposed others. Spot maps are 

made using maps and markers representing each case (e.g., 

push pins) to show the locations where each case spent time. 

Figure 9.2 shows an example of a spot map. Another option is 

to create a diagram with structures that represent each location 

where cases spent time.

Figure 9.2—Sample spot map. In this map, the pins represent outbreak cases. Each case is mapped to locations 

where they spent time.

Module 9—Tuberculosis Outbreak Detection and Response 

24
Important patterns often become visible when lines showing 

connections between the cases are added to the spot map 

or diagram. For example, having several cases linked to 

one location (e.g., the same apartment complex, church, or 

workplace) suggests transmission may have happened at that 

location.

If multiple cases cannot be connected to a single location, it 

could suggest that transmission happened at several different 

locations or that an important common location has not yet 

been identified. 

Characterizing Outbreaks by Time

With TB, outbreaks are typically characterized in terms 

of months, calendar quarters, or even years. Using visual 

representations to describe outbreaks over time is often very 

useful. 

Two commonly used representations of time are

 An epidemic curve (epi curve) 

 A plot of infectious periods

Epi Curve

An epi curve is a graph that displays the number of TB cases 

and when they were identified. Time is plotted on the horizontal 

x-axis and the number of cases is plotted on the vertical y-axis.

The shape of the epi curve often gives clues about whether 

the majority of transmission occurred early in the outbreak or 

whether there is still ongoing transmission. An epi curve with 

a steep up slope and a gradual down slope indicates a single 

source case (or “point source”) to which cases were exposed 

(Figure 9.3). If the epi curve has a plateau instead of a peak, 

this indicates that the outbreak is ongoing (Figure 9.4). This 

scenario is troubling because it suggests that the outbreak is not 

under control.

Important patterns 

often become visible 

when lines showing 

connections between the 

cases are added to the 

spot map or diagram.

The shape of the epi curve 

often gives clues about 

whether the majority of 

transmission occurred 

early in the outbreak 

or whether there is still 

ongoing transmission.

Module 9—Tuberculosis Outbreak Detection and Response 

25
Figure 9.3—Epi-curve for a TB outbreak with a point source.

Figure 9.4—Epi-curve for a TB outbreak with ongoing transmission.

9

8

7

6

5

4

3

2

1

0

Example of a Point Source Outbreak

Jan

2011

Jul

2011

Jan

2012

Jul

2012

Jan

2013

Jul

2013

Cases

9

8

7

6

5

Cases

4

3

2

1

0

Example of an Ongoing Outbreak

Jan

2011

Jul

2011

Jan

2012

Jul

2012

Jan

2013

Jul

2013

Module 9—Tuberculosis Outbreak Detection and Response 

26
Plot of the Infectious Periods

Another way to model the time course of a TB outbreak is 

to make a diagram that shows the infectious period of each 

outbreak case.

A plot of the infectious periods shows the overall duration 

of the outbreak, beginning with start date of the first case’s 

infectious period. To make a plot of the infectious periods, 

time is plotted on the horizontal x-axis. The vertical y-axis of 

the diagram lists the outbreak cases in the order they were 

identified (i.e., beginning with the first case at the top and the 

most recently identified case at the bottom).

A horizontal bar representing the infectious period for each case 

is then created. The left-side border of the bar represents the 

start of the infectious period. The right-side border represents 

the end of the infectious period. Figure 9.5 shows an example 

of a plot of infectious periods. 

Descriptive epidemiology tools can be even more powerful 

when they are combined. For example, incorporating 

information from the spot map into the plot of the infectious 

A plot of the infectious 

periods shows the overall 

duration of the outbreak, 

beginning with start 

date of the first case’s 

infectious period.

Figure 9.5—Plot of infectious periods for outbreak cases.

Plot of the Infectious Periods for Cases Involved in TB Outbreak

Case 1

Case 2

Case 3

Case 4

Jan

2012

Apr

2012

Oct

2012

Jul

2012

Apr

2013

Jan

2013

Jul

2013

Oct

2013

Module 9—Tuberculosis Outbreak Detection and Response 

27
Figure 9.6—Plot of the infectious periods with information from the spot map incorporated.

periods can help narrow down when exposure happened at 

certain locations. This information can be used by investigators 

to determine the need for active case-finding and location-based 

contact investigation activities at those locations. Figure 9.6 

shows a plot of infectious periods with information from a spot 

map incorporated.

Plot of the Infectious Periods for Cases Involved in TB Outbreak

with Locations Identified in Spot Map

Jan

2012

Apr

2012

Oct

2012

Jul

2012

Apr

2013

Jan

2013

Jul

2013

Case 1

Case 2

Case 3

Case 4

Case 4 stayed in Case 3’s home

Oct

2013

Case 1

spent

time with

Case 4 in

jail

Module 9—Tuberculosis Outbreak Detection and Response 

28
Compile Contact Investigation Results for Each of the 

Outbreak Cases 

After compiling information on outbreak cases, investigators 

should carefully examine all available contact investigation 

results for each case. This is because by the time an outbreak is 

recognized, many individual contact investigations have already 

taken place. Investigators need to identify the locations of all 

the available contact investigation data and determine how to 

integrate those various sources.

Compiling and analyzing contact investigation results can help 

focus initial outbreak investigative efforts on the most infectious 

cases. For example, in an outbreak with numerous cases, only 

two cases may be responsible for most of the TB transmission. 

The activities and contacts of those two cases can then be 

prioritized as the outbreak investigation proceeds. 

Another important purpose of this analysis is to assess the 

completeness of the initial contact investigations. This can help 

identify which cases may have had too few contacts identified 

during their contact investigation.

Compiling and analyzing 

contact investigation 

results can help focus initial 

outbreak investigative 

efforts on the most 

infectious cases.

Module 9—Tuberculosis Outbreak Detection and Response 

29
Study Questions 9.8–9.

9.8 What is descriptive epidemiology?

9.9 What is a spot map?

9.10 What are two ways investigators can characterize TB outbreaks by time?

9.11 Why is it important to compile the individual contact investigation results for each 

outbreak case?

Answers to study questions are on pages 59– 63 

Module 9—Tuberculosis Outbreak Detection and Response 

30
Case Study 9.

Keith is a health care worker at the local health department, and he has been assigned to 

investigate a TB outbreak. Using the information from the outbreak line list, he created an epi 

curve (below). 

For accessible explanation of graph below, see Appendix for Accessibility on page 67.

What does the shape of the epi curve tell Keith about the outbreak? 

Answers to case studies are on pages 64– 66

9

8

7

6

5

4

3

2

1

0

Epi Curve for TB Outbreak

Jan

2011

Jul

2011

Jan

2012

Jul

2012

Jan

2013

Jul

2013

Module 9—Tuberculosis Outbreak Detection and Response 

31
Case Study 9.

You are a health care worker at the local health department and have been assigned to 

investigate a TB outbreak. Using the line list below, plot each case on the map at each location 

they have been connected to. 

Does it appear as though there are any locations where cases spent time together that may 

need further investigation? 

Case Identifier Demographics Genotype Location

Case A M, 35 years old G54321 Home 1, Jail, Work site

Case B M, 46 years old G54321 Homeless Shelter

Case C M, 37 years old G54321 Tavern, Homeless Shelter, Jail

Case D F, 48 years old G54321 Home 2

Case E F, 25 years old G54321 Tavern

Case F M, 50 years old G54321 Homeless Shelter, Home 2

For accessible explanation of map below, see Appendix for Accessibility on page 67.

Answers to case studies are on pages 64– 66

Module 9—Tuberculosis Outbreak Detection and Response 

32
Step 4: Convene the Outbreak Response Team and 

Develop the Outbreak Hypotheses 

Successful outbreak responses require the combined effort of 

multiple individuals and organizations, both within and outside 

the health department.

Convening the Outbreak Response Team

The role of the outbreak response team is to investigate and 

control the TB outbreak. If a TB outbreak manager has not 

already been designated, one should be identified at this 

time. Ideally, this person will serve in this role for the entire 

outbreak response. The TB outbreak manager must have the 

authority to redirect resources and assign staff to outbreak 

response activities, as well as coordinate efforts among all of the 

individuals, organizations, and stakeholders involved. 

A TB outbreak response team may be comprised of persons 

such as

 Staff from the local health department who are usually 

involved in TB contact investigations, including the TB 

program manager, nurse case managers, and field-based 

staff, as well as persons who may work in other parts of 

the health department, such as database managers, STD 

investigators, outreach workers, and epidemiologists 

 State TB controller, TB program manager, TB nurse 

consultant, TB epidemiologist, TB genotyping coordinator, 

and public health laboratory representative

 Public information officers for the local and state health 

departments

 Support personnel

 CDC, by request

The actual job titles for TB outbreak response team members 

may vary by jurisdiction. In smaller jurisdictions, one staff 

member often fills several roles. The outbreak response team 

could also include community partners (e.g., hospital infection 

control personnel or jail medical staff). Generally, the more 

individuals and organizations involved, the greater the need to 

clarify roles and responsibilities.

The initial meeting of the outbreak response team typically 

involves

 Reviewing information about the outbreak, including the 

case definition, the line list, descriptive epidemiology, and 

contact investigation results for each case.

A TB outbreak manager 

should be identified.

Module 9—Tuberculosis Outbreak Detection and Response 

33
 Developing the initial outbreak hypotheses. 

 Reviewing the standing outbreak response plan and making 

any necessary modifications to suit the current outbreak.

 Setting the response priorities, clarifying the roles and 

responsibilities of individuals and programs involved, and 

addressing any jurisdictional issues that may be anticipated.

 Establishing timeframes and methods for investigation 

activities, data collection, and management. 

 Establishing a schedule for case conferences or meetings to 

review challenges and progress.

 Establishing a communication plan among staff and others 

involved in the investigation. This may include determining 

preferences for routine communications, both for day-to-day 

work assignments within the outbreak response team, and 

for more general updates between the team and upper level 

management. 

 Determining potential media interest.

 Discussing external communication plans (refer to Step 7). 

Developing the Outbreak Hypotheses

Investigators usually start to develop ideas about how and 

why an outbreak could have happened as soon as they hear 

about a potential outbreak. These theories are called outbreak 

hypotheses. 

The team manager should lead a discussion to refine these 

initial outbreak hypotheses (Figure 9.7). This discussion should 

include frontline TB staff who are most familiar with the 

situation. Frontline staff bring valuable observations, insights, 

and intuitions about the outbreak.

In discussing the outbreak hypotheses, the outbreak response 

team relies on their collective knowledge about 

 TB (e.g., mode of transmission, pathogenesis, TB risk 

factors)

 Cases that meet the outbreak case definition (i.e., the line 

list)

 Descriptive epidemiology 

 Contact investigation results

Describing each case’s infectious period, the case(s) to which 

they are known to be epi linked, and their contact investigation 

results is important for analyzing outbreak data. This analysis 

can help generate and test hypotheses about who spread TB to 

whom, when, and where. 

Outbreak hypotheses are 

theories about how, when, 

and where TB transmission 

may have occurred 

during an outbreak.

Module 9—Tuberculosis Outbreak Detection and Response 

34
As the team discusses the various initial outbreak hypotheses, 

they will begin to identify the gaps where more information 

is needed to confirm or refute those hypotheses. The TB 

outbreak manager then uses those information gaps to 

determine the initial response priorities and to assign activities 

to various team members.

Subsequent meetings of the outbreak response team are 

usually held on a regular basis throughout the response. 

Figure 9.7—An outbreak response team discussing the outbreak hypotheses.

Module 9—Tuberculosis Outbreak Detection and Response 

35
Step 5: Fill Information Gaps

In Step 5, the outbreak response team needs to confirm or 

collect new information (i.e., fill in information gaps) based on 

the initial outbreak hypotheses. The line list should be updated 

with the additional information learned up to this point. For 

example, throughout the investigation, investigators may identify 

new cases that meet the outbreak case definition that need to 

be added to the line list. Creating new versions of the line list, 

dating the versions, and having a system to ensure everybody 

on the team receives the updated list, can help avoid confusion 

about which version is the most current.

Public health programs can gather additional information about 

cases and outbreaks in a number of ways, including

 Performing public record searches 

 Re-interviewing cases and contacts

 Repeating field visits and visiting new sites

 Updating clinical findings and laboratory results for cases 

and contacts

 Cross-matching the line list with homeless shelter and 

correctional facility records

Performing Public Record Searches

Performing public record searches (e.g., internet social network, 

arrest records, and other public notices) with names of cases 

and their contacts can help identify other potentially useful 

information, such as similarities and connections among cases in 

the outbreak.

Re-interviewing Cases and Contacts

Re-interviewing cases and contacts is essential for confirming 

information and for identifying locations, activities, or behaviors 

not discussed in earlier interviews. Offering incentives and 

enablers to help encourage cooperation with re-interviews can 

be effective and should be considered.

Depending on the number of cases, it can be helpful to have 

one experienced investigator do as many of the interviews as 

possible, because a single interviewer is more likely to notice 

important similarities. However, if an investigator is not able 

to elicit key information, switching investigators for selected 

interviews should be considered.

When re-interviewing cases and contacts as part of an outbreak 

investigation, the time frame of interest is not only each case’s 

infectious period, but also their potential exposure periods 

The outbreak response 

team needs to confirm or 

collect new information 

based on the initial 

outbreak hypotheses.

Re-interviewing cases and 

contacts is essential for 

confirming information 

and for identifying 

locations, activities, or 

behaviors not discussed 

in earlier interviews.

Module 9—Tuberculosis Outbreak Detection and Response 

36
(i.e., when and how they became infected, before they developed 

TB disease). Interview questions should cover the time frame 

used in the outbreak case definition (Step 2).

A standardized approach to re-interviewing, such as using 

an interview checklist, can help the outbreak response team 

systematically collect information about cases’ relationships, 

activities, or interests. To understand the possible transmission 

opportunities among cases, questions should be asked about any 

behaviors, activities, or locations that may be associated with the 

outbreak (e.g., specific alcohol or drug usage sites).

Having the team work together to develop this interview 

checklist before starting the re-interviews helps ensure that 

the same questions are asked of everyone, even if several 

investigators are working simultaneously. However, investigators 

should not limit themselves to just the predetermined questions. 

Pursuing additional and creative lines of questioning should be 

encouraged whenever it may be helpful to do so.

New information learned during the interview should be 

recorded and shared at the next outbreak response team meeting. 

Any activities or locations identified by one case should be 

systematically incorporated into follow-up interviews with other 

outbreak cases. Multiple re-interviews may be necessary to 

ensure all cases are asked about certain activities or locations 

that emerge as potentially important aspects of the outbreak. 

Interview forms are usually revised frequently during an 

investigation to incorporate new questions.

Repeating Field Visits and Visiting New Sites

Repeat field visits can help the outbreak response team collect 

new information or confirm information that was collected 

previously (Figure 9.8). If any new potential transmission sites 

have been identified, visits to those sites should be made as soon 

as possible. 

It can be helpful to find out about privacy and confidentiality 

requirements of both the health department and the external 

partner in advance of these field visits, particularly if discussion 

or sharing of the names on the outbreak line list (e.g., for crossmatching of records) is anticipated.

As with contact investigation field visits, public health staff 

should use the visit as an opportunity to educate persons at that 

site about the basics of TB transmission and pathogenesis, and 

the importance of testing and treatment for TB disease and LTBI. 

Staff at the facility should be alert for any persons with symptoms 

of TB disease and refer them for immediate medical assessment. 

Any activities or locations 

identified by one case 

should be systematically 

incorporated into followup interviews with 

other outbreak cases.

When re-interviewing cases 

and contacts as part of an 

outbreak investigation, the 

time frame of interest is not 

only each case’s infectious 

period, but also their 

potential exposure periods 

(i.e., when and how they 

became infected, before 

they developed TB disease).

Module 9—Tuberculosis Outbreak Detection and Response 

37
Investigators should work with staff to record names (if 

available) and locating information for any additional contacts 

needing assessment who were not previously identified.

During the outbreak investigation field visit, additional emphasis 

should be placed on identifying similarities among the cases 

associated with that site, such as dates, times, or activities.

Investigators should observe environmental characteristics of 

the site such as room size, crowding, ventilation, low ceilings, 

and dense air. These characteristics can help assess where 

transmission was likely to occur.

In some situations, the investigator will have the opportunity 

to take photographs of the site or obtain copies of records 

(e.g., homeless shelter logs, incarceration histories, floor plans). 

Equipment such as a camera or USB flash drive can be helpful 

to bring on field visits. (For more information on field visits, 

refer to Module 8, Contact Investigations for Tuberculosis.)

During the outbreak 

investigation field visit, 

additional emphasis should 

be placed on identifying 

similarities among the 

cases associated with 

that site, such as dates, 

times, or activities.

Figure 9.8—Outbreak investigator conducting a repeat field visit.

Module 9—Tuberculosis Outbreak Detection and Response 

38
Updating Clinical and Laboratory Information about the 

Cases and Contacts

Throughout the investigation, it is essential that the outbreak 

line list and contact findings are kept up-to-date.

It is not unusual for some of the clinical or laboratory 

information about cases to be pending during the early stages 

of the investigation. For example, genotyping results should be 

obtained for all cases suspected of being part of the outbreak. 

TB genotyping can be obtained by public health programs in 

the United States for most prior culture-positive cases as long as 

the isolates are still available in storage. Once these results are 

available, they should be added to the line list.

Throughout the outbreak investigation, the outbreak response 

team will be working to ensure that priority contacts whose 

assessments were previously incomplete are found, assessed, 

and, if needed, begin treatment. The team should also work 

to identify new contacts who were previously overlooked. 

Investigators should ensure that information regarding contacts 

is recorded in the public health record.

Cross-Matching the Line List with Homeless Shelter and 

Correctional Facility Records

Because many outbreaks are linked to homeless shelters and 

correctional facilities, interviews with cases should include 

questions about recent homelessness and incarceration. 

Interviewers should ask about approximate dates of stay at any 

homeless shelters, local jails, or other prison systems identified 

previously. However, because some cases may not reliably 

self-report their homeless shelter stays or recent incarceration 

history, a systematic cross-matching of all the names on the 

line list with homeless shelter and correctional facility records 

should be done. This is to both confirm what was discussed 

during the interview and to learn about additional stays that 

would otherwise be missed. In some situations, cross-matching 

cases by date of birth may be more productive than crossmatching by name.

As information gaps are filled based on the initial outbreak 

hypotheses, the outbreak response team should meet again and 

ensure new findings are shared with the team manager and 

other team members, particularly those involved in data entry 

and management. 

Cases may not reliably 

self-report their homeless 

shelter stays or recent 

incarceration history.

Module 9—Tuberculosis Outbreak Detection and Response 

39
Study Question 9.1

9.12 List five ways investigators can “fill information gaps” related to a TB outbreak.

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

40
Step 6: Implement the Specific 

Outbreak Response Plan

Although Steps 1 through 5 focused on cases, the emphasis 

at this step shifts more to finding contacts, assessing them for 

TB infection and disease, and preventing additional outbreak 

cases. To control the outbreak, the outbreak response team 

must find contacts with undiagnosed TB disease before they 

cause additional transmission. Finding contacts as part of TB 

outbreak response is similar to how it is done for a TB contact 

investigation, but on a much larger scale.

Based on the outbreak hypotheses, the team should target 

certain contacts or populations for active TB case finding. The 

activities should focus on the cases or sites that appear to 

have had the most transmission. Active TB case finding should 

include symptom reviews and chest radiographs, in addition to 

testing for TB infection.

Additional activities that may occur during the TB outbreak 

response include

 Extending hours of clinic services to accommodate the 

increased number of referrals, particularly for persons who 

are only available outside the health department’s usual 

hours of operation;

 Providing transportation for cases and contacts to the health 

department;

 Providing offsite services during nights and weekends;

 Providing DOT to a larger number of persons (e.g., not 

only cases, but also infected contacts at risk for rapid 

development of TB disease); and

 Offering incentives and enablers to accomplish active casefinding, contact assessment, and treatment completion goals.

Successful implementation of the outbreak response plan 

requires careful attention to the following:

 Ensuring adequate resources for implementing the outbreak 

response activities

 Using a standardized approach to collect and manage 

investigation data 

 Directing the specific response activities based on the 

evolving findings of the investigation

The emphasis at this step 

shifts more to finding 

contacts, assessing them 

for TB infection and 

disease, and preventing 

additional outbreak cases.

Module 9—Tuberculosis Outbreak Detection and Response 

41
Ensuring Adequate Resources for Implementing the 

Outbreak Response Activities

Responding to an outbreak can often overwhelm existing local 

public health capacity.

Many local health departments may not have the resources and 

staff to perform the above activities. To ensure adequate human 

resources, health departments may need to

 Reassign public health staff from their usual duties and train 

them to help with outbreak-related activities; 

 Access additional clinicians with TB expertise to review 

chest x-rays, evaluate contacts, and manage suspected cases 

and infected contacts; and

 Recruit outreach workers with special skills (e.g., specific 

linguistic or cultural competencies, ability to place and read 

TSTs, draw blood for IGRAs, DOT experience) to assist with 

interviews, assessment, and treatment.

It is important to remember that community partners (e.g., 

hospital infection control personnel, jail medical staff) can also 

become overwhelmed by the additional workload created by TB 

outbreaks. There are often surges in diagnostic and laboratory 

examinations and greater demand for facilities (e.g., airborne 

infection isolation) for the evaluation and treatment of suspected 

cases. The health department should consider including such 

partners on the TB outbreak response team from the very 

beginning of the response.

Managing resources effectively during an outbreak requires 

frequent communication between the TB outbreak manager 

and health department leadership. For this reason, a review 

of current resources and anticipated shortfalls are typically 

discussed at each outbreak response team meeting. 

When it is anticipated that responding to a TB outbreak is 

likely to disrupt other essential TB control functions, requests 

for supplemental resources and assistance should not be 

delayed. Additional resources could include other agencies, 

such as neighboring local health departments or the state health 

department. CDC can assist with TB outbreak response at the 

request of the state health department, another federal agency, 

or a sovereign entity such as an American Indian tribe or a U.S. 

territory.

Community partners 

(e.g., hospital infection 

control personnel, jail 

medical staff ) can also 

become overwhelmed by 

the additional workload 

created by TB outbreaks.

When it is anticipated 

that responding to a 

TB outbreak is likely to 

disrupt other essential 

TB control functions, 

requests for supplemental 

resources and assistance 

should not be delayed.

Module 9—Tuberculosis Outbreak Detection and Response 

42
Using a Standardized Approach to Collect and Manage 

Outbreak Data 

The size and scope of information about cases and contacts 

generated during outbreak investigations can quickly become 

unmanageable. Even though TB outbreaks typically involve 

several overlapping contact investigations, the processes and 

systems used for managing data for TB contact investigation 

may not be adequate for outbreak investigations. 

Some of the challenges to managing information during 

outbreak investigations are caused by differences in the amount 

and types of contact investigation information previously 

collected for each outbreak case. For example:

 Contacts and cases could have been exposed to more than 

one outbreak case;

 Contacts who were previously assessed and found not to 

have TB infection could have been re-exposed and may 

need to be reassessed; or

 Cases or contacts who recently completed treatment 

sometimes have been subsequently re-exposed and 

potentially re-infected.

Once information from the various contact investigations has 

been collected, a system should be created and maintained to 

keep up with the large amount of new data expected from TB 

outbreak response activities. A pooled contact roster should be 

considered, where all contacts for the outbreak are accumulated 

and tracked in one list. Health department leadership should 

consider designating a person with data management and 

epidemiology skills to assist the outbreak response team with 

a process to systematically enter, manage, and analyze the 

outbreak data.

As with contact investigations, using standardized approaches 

to collecting and managing information during outbreak 

investigations can be very helpful. Ideally, approaches to data 

management will define

 What information will be collected, and why;

 Who is responsible for collecting information, and how it 

will be collected; and

 How information will be managed after it is collected.

Being able to systematically track cases and contacts over time 

is facilitated by the use of information technology such as 

spreadsheet software. Ideally, key users will be familiar with the 

software before the investigation begins. 

Some of the challenges 

to managing information 

during outbreak 

investigations are caused 

by differences in the 

amount and types of 

contact investigation 

information previously 

collected for each 

outbreak case.

Module 9—Tuberculosis Outbreak Detection and Response 

43
Directing the Specific Response Activities Based on the 

Evolving Findings of the Investigation

Findings from the outbreak investigation activities should 

be monitored and interpreted on a regular basis to keep 

the investigation on track. It can be helpful to have ongoing 

assistance from an epidemiologist familiar with the outbreak and 

the investigation.

New findings should be discussed at outbreak response team 

meetings. This will help the outbreak manager make decisions 

about whether the current outbreak response plan needs to be 

readjusted.

Module 9—Tuberculosis Outbreak Detection and Response 

44
Study Question 9.1

9.13 List at least 5 activities health departments may need to implement to respond to 

an outbreak.

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

45
Step 7: Communicate Interim Findings 

Effective outbreak responses require a high degree of 

collaboration among internal and external partners. Thus, it is 

critical to communicate findings in a timely and appropriate 

way, and ensure any resulting changes to outbreak investigation 

and response plans are reported to team members, stakeholders, 

and partners. 

Because TB outbreak response is such an intensive undertaking, 

health department staff may become so busy with the day-today activities of the response that external communications are 

neglected. Having public information officers present at the first 

meeting of the outbreak response team (Step 4) helps ensure 

planning for external communications.

Communicating with the Outbreak Team

The discussion at the initial meeting of the outbreak response 

team (Step 4) should result in an initial communication plan, 

which is often adapted over time based on what works best. For 

example, there might be 

 Daily email updates to the response team summarizing 

the current priorities, activities, and individual team 

assignments; 

 Weekly email updates or conference calls with upper level 

management; and 

 Less detailed summaries for external stakeholders and 

partners every 2 to 3 weeks. 

Communicating with Stakeholders and External Partners 

It is important to identify and collaborate with key stakeholders 

and external partners. Some examples of stakeholders and 

external partners during a TB outbreak are

 Cases, their family members, and their contacts; 

 Institutions involved in the outbreak (e.g., hospitals, jails, 

homeless shelters);

 Community groups and organizations that provide services 

to the populations involved in the outbreak;

 Public health officials from various agencies and, in some 

situations, potentially other local or state government 

officials;

 Experts in medical and non-medical management of cases 

and contacts (e.g., physicians, nurses, public health workers, 

other health care providers); and

Effective outbreak 

responses require a high 

degree of collaboration 

among internal and 

external partners.

Having public information 

officers present at the first 

meeting of the outbreak 

response team helps ensure 

planning for external 

communications.

Module 9—Tuberculosis Outbreak Detection and Response 

46
 Directors, managers, and personnel of programs and 

facilities that provide diagnostic, isolation, and treatment 

services to the populations involved in the outbreak.

New and important stakeholders and external partners are often 

identified over the course of the outbreak investigation. When 

this happens, every effort should be made to appropriately 

engage them in response efforts. 

Stakeholder and external partner collaboration enables public 

health investigators to

 Offer onsite education about TB;

 Access records at potential transmission sites; and 

 Develop and deliver coordinated media messages that aid 

the investigation.

Such partnerships also help the health department gain 

important insight into the culture of persons involved in the 

outbreak and the barriers they may face in obtaining TB 

information, screening, and treatment. Ultimately, identifying 

and addressing these barriers could prevent future TB outbreaks 

by reducing instances of delayed or missed diagnosis of TB 

disease. 

Communicating with the Media

TB outbreaks often result in attention and requests for 

information from the media. This is because TB outbreaks 

can sometimes cause feelings of fear, anger, and helplessness 

in both the affected communities (e.g., TB cases and their 

contacts, staff and volunteers of potential transmission sites) 

and the general population who might have heard about the 

outbreaks. Sources of information (e.g., media reports) that are 

factually accurate and that correctly describe the role of the 

health department can help to dispel stigma, alleviate undue 

anxiety, generate support for TB control efforts, and, in time, 

facilitate the outbreak investigation process. Collaboration 

with stakeholders and other external partners to prepare and 

disseminate information during outbreaks can help ensure 

it is accurate, helpful, culturally appropriate, and that it is 

coordinated with their own internal and external messages. 

Training resources are available to enhance the media 

communication skills of public health workers. These include

 The World Health Organization and Stop TB Partnership 

Working with the Media: How to Make Your Messages on 

Tuberculosis Count, which can be accessed online at 

www.stoptb.org/assets/documents/resources/publications/

acsm/Working%20with%20the%20Media%20Final%20Web.pdf 

Partnerships can help the 

health department gain 

important insight into the 

culture of persons involved 

in the outbreak and the 

barriers they may face in 

obtaining TB information, 

screening, and treatment.

Sources of information 

(e.g., media reports) that 

are factually accurate and 

that correctly describe 

the role of the health 

department can help to 

dispel stigma, alleviate 

undue anxiety, generate 

support for TB control 

efforts, and, in time, 

facilitate the outbreak 

investigation process.

Module 9—Tuberculosis Outbreak Detection and Response 

47
 CDC Forging Partnerships to Eliminate Tuberculosis, 

2007, which can be accessed online at www.cdc.gov/tb/

publications/guidestoolkits/forge/default.htm

 CDC Crisis and Emergency Risk Communication (CERC), 

which can be accessed online at https://emergency.cdc.gov/

cerc/index.asp

Step 8: Summarize the Outbreak Response 

As the outbreak response nears completion, a summary of the 

outbreak response activities should be prepared. Depending on 

the intended uses, this summary could take the form of a formal 

written report or a public presentation. 

The purposes of preparing the summary are to

 Ensure internal and external partners have updated 

information about the investigation and findings; and 

 Provide recommendations for moving forward.

The use of tables, figures, and other descriptive epidemiology 

methods can ensure findings are presented in a clear and 

concise manner. Seeking the assistance and consultation of 

epidemiologists in preparing and reviewing these summary 

reports can be very helpful.

Summaries typically include a description of the following:

 The outbreak case definition 

 Sources of information and investigation methods

 Size and scope of the outbreak 

 Non-identifying descriptions of outbreak cases, that 

include information such as ages, dates and methods of 

identification, infectious periods, and treatment status

 Chains of transmission

 Contributing factors and risk factors associated with the 

outbreak

 Activities and findings, including number of contacts 

identified, assessed, and treated for LTBI, and number of 

additional cases found

 Activities yet to be completed

This outbreak summary will inform Steps 9 and 10.

The purposes of preparing 

the summary are to 

ensure internal and 

external partners have 

updated information 

about the investigation 

and findings and to 

provide recommendations 

for moving forward.

Module 9—Tuberculosis Outbreak Detection and Response 

48
Study Questions 9.14– 9.

9.14 What are some benefits of engaging stakeholders and partners in outbreak 

response efforts? 

9.15 What is the purpose of developing an outbreak summary?

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

49
Case Study 9.

The health department in Purple County has been investigating and responding to an 

outbreak at a local factory. Eight employees have been diagnosed with TB disease. Most of the 

employees are foreign-born. The health department was initially alerted to the outbreak by an 

astute emergency room physician. 

Who are some potential stakeholders and partners the health department should reach out to? 

Answers to case studies are on pages 64– 66

Module 9—Tuberculosis Outbreak Detection and Response 

50
Step 9: Implement Recommendations

Outbreak response summaries are usually followed by the 

outbreak response team’s recommendations on how to 

proceed. Developing effective and appropriate TB control 

recommendations after an outbreak can be challenging. In 

addition to the strain that the TB outbreak has already placed 

on public health resources, it is not unusual to have an increase 

in cases toward the end of the investigation, often as a result 

of heightened awareness and enhanced active case-finding 

activities.

In addition, TB disease progression in unidentified or untreated 

infected contacts means that it may take 2 to 3 years before 

improvements in TB control are clearly apparent. Sustained 

resources and responsiveness until the outbreak is fully under 

control are necessary.

Recommendations are typically organized into immediate and 

longer term activities. Immediate recommendations usually 

emphasize the completion of TB prevention and control 

activities already underway. These activities could include 

active case-finding, contact assessments, and ensuring complete 

treatment for persons found to have TB disease or latent TB 

infection.

Longer term recommendations may outline

 Policies and procedures for improved TB prevention and 

control in settings and populations identified during the 

investigation as at risk;

 Post-outbreak genotype monitoring for the recurrence of the 

outbreak, such as with TB GIMS watch lists;

 Improved TB control program capacity and access to 

additional TB training for public health staff and community 

partners; and

 Program gaps that could be addressed to help prevent 

future outbreaks of TB.

Many public health departments will choose to prioritize postoutbreak recommendations, phasing them in according to the 

capacity of their TB control programs. Ongoing, enhanced 

collaboration with internal and external partners is almost 

always needed.

As recommendations are implemented, outcomes should be 

monitored and documented via progress reports or other 

methods. This is important for determining whether the 

recommendations are working and being implemented as 

Recommendations are 

typically organized into 

immediate and longer 

term activities. Immediate 

recommendations usually 

emphasize the completion 

of TB prevention and 

control activities 

already underway.

Sustained resources and 

responsiveness until the 

outbreak is fully under 

control are necessary.

As recommendations are 

implemented, outcomes 

should be monitored and 

documented via progress 

reports or other methods.

Module 9—Tuberculosis Outbreak Detection and Response 

51
recommended. Regular epidemiologic review may also reveal 

ways the recommendations could be improved or made more 

effective. Some activities may be scaled back, while others may 

be given greater attention.

Step 10: Evaluate the Outbreak Response

Evaluating TB outbreak response efforts provides public health 

programs opportunities to recognize what went well during the 

response and how future outbreak responses may be done more 

effectively.

Outbreak investigation and response evaluations can occur 

collaboratively during a meeting of representatives from the 

public health department and the internal and external partners 

involved in the investigation. An initial meeting should take 

place soon after the closure of the outbreak response. 

During evaluation meetings, participants should review 

important findings and discuss lessons learned during the 

investigation. A collaborative approach to evaluation is 

especially important for investigations involving multiple 

agencies or multiple jurisdictions. 

In advance of these meetings, the most recent Outbreak 

Investigation Summary (see Step 8) is typically circulated. 

Reviewing the summary at the start of the meeting provides 

participants opportunities to

 Clarify information from the report and updates;

 Provide feedback about the report; and 

 Share additional information.

Topics for discussion during evaluation meetings typically 

include

 Factors that contributed to the outbreak, such as delays in 

diagnosis of source cases or involvement of hard-to-reach 

populations

 What was learned during the investigation, including

 Which areas of the TB control program are working well 

and which might be in need of improvement

 What barriers to outbreak detection or investigation were 

encountered

 How partnerships and collaboration strategies affected 

the effectiveness of the investigation

 What is left to be done 

Evaluating TB outbreak 

response efforts provides 

public health programs 

opportunities to recognize 

what went well during the 

response and how future 

outbreak responses may 

be done more effectively.

Module 9—Tuberculosis Outbreak Detection and Response 

52
TB control programs may consider formally recognizing the 

efforts of partner organizations and individual staff. The use of 

certificates of recognition and individualized thank-you letters 

can be an important and meaningful way to recognize their 

contributions to the outbreak investigation. 

Communicating Findings to the Broader Public 

Health Community

Outbreak response summaries can also serve as references if the 

health department encounters a similar situation in the future. 

Response summaries that are shared beyond the local or state 

public health infrastructure could make important contributions 

to TB control efforts in other jurisdictions. These summaries can 

also form the basis for developing a future publication in the 

scientific literature. 

Response summaries that 

are shared beyond the 

local or state public health 

infrastructure could make 

important contributions 

to TB control efforts in 

other jurisdictions.

Module 9—Tuberculosis Outbreak Detection and Response 

53
Study Questions 9.16– 9.

9.16 List at least two examples of longer-term outbreak response recommendations.

9.17 List the ten steps of the systematic approach to TB outbreak investigations.

Answers to study questions are on pages 59– 63

Module 9—Tuberculosis Outbreak Detection and Response 

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Special Circumstances in TB Outbreak 

Detection and Response

The following section reviews some situations where TB 

outbreaks can be difficult to detect or respond to including

1. Health care settings

2. Correctional and detention facilities

3. Cases with weakened immune systems

Health Care Settings

Transmission of M. tuberculosis and subsequent outbreaks of TB 

involving health care settings have been associated with

 Delayed recognition of signs and symptoms consistent with 

TB disease

 Delayed isolation precautions or effective TB treatment

 Intermingling of patients with undiagnosed TB disease 

with patients who have medical risk factors for rapid 

development of TB disease

 Inadequate infection control measures, such as 

 Inadequate isolation facilities, including lack of airborne 

infection isolation rooms

 Recirculation of air from respiratory isolation rooms to 

other parts of the hospital

 Failure to isolate patients until they are no longer 

infectious

 Allowing isolated patients to leave their rooms without 

wearing a mask

 Leaving isolation room doors open

TB outbreaks involving health care settings can involve large 

numbers of contacts (e.g., hospital staff, other patients, visitors, 

volunteers) and multiple jurisdictions (e.g., occupational 

health, community public health, and other medical providers). 

Typically, health care staff will be screened by the occupational 

health service and inpatients will be screened by the health care 

facility. Visitors, volunteers, and others are usually assessed by 

community public health or their personal physicians.

Module 9—Tuberculosis Outbreak Detection and Response 

55
When responding to TB outbreaks involving health care 

facilities, it is critical to ensure the results of all contact 

assessments are monitored by the public health department 

responsible for the investigation.

Guidelines for the prevention of transmission of M. tuberculosis

in health-care settings were published in 2005. This document is 

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

encouraged to review the guidelines and to ask for assistance 

in their interpretation, if necessary. In the United States, local 

public health programs should consult with the next higher 

level of public health administration, which is generally the state 

health department. State programs can consult with CDC for 

additional assistance.

Correctional and Detention Facilities

There is a higher prevalence of TB disease among persons 

associated with correctional and detention facilities because of

 Over-crowded and poorly ventilated conditions, which can 

increase risk for transmission of M. tuberculosis; and 

 A higher prevalence of risk factors that increase the risk for 

having TB infection, as well as the risk for progression to 

TB disease after infection with M. tuberculosis.

Frequent transfers and movements within or among facilities can 

also add to the challenges of detecting cases and outbreaks, and 

assessing and managing contacts.

The risk for TB infection and TB disease is not limited to 

current or former residents of correctional or detention 

facilities. Infected staff can go on to develop TB disease and 

spread M. tuberculosis in the community. Visitors and persons 

from programs associated with correctional or detention 

facilities, such as courthouses or programs providing health 

and dental care, are also at risk. Thus, collaboration between 

the community public health department and a variety of 

key stakeholders, including administrators of the health care 

and occupational health programs of the involved facilities, is 

critical.

Recommendations for the prevention and control of TB in 

correctional and detention facilities were published in 2006. This 

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

Programs are encouraged to review the recommendations and 

to ask for assistance in their interpretation if necessary.

When responding to 

TB outbreaks involving 

health care facilities, it 

is critical to ensure the 

results of all contact 

assessments are monitored 

by the public health 

department responsible 

for the investigation.

Collaboration between 

the community public 

health department and a 

variety of key stakeholders, 

including administrators 

of the health care and 

occupational health 

programs of the involved 

facilities, is critical.

Module 9—Tuberculosis Outbreak Detection and Response 

56
Cases with Weakened Immune Systems

Detecting or preventing TB disease in persons with a weakened 

immune system can be difficult. Such persons are at greater risk 

for rapid development of TB disease once infected. Also, some 

immune-suppressing diseases and disorders can interfere with 

the sensitivity of symptom screening, TST, and chest x-rays. 

Delays in treatment of TB infection can result in development of 

TB disease.

Another important consideration when investigating outbreaks 

that involve immunosuppressed cases is that their contacts 

are also likely to be immunosuppressed. For example, cases 

with diabetes and renal failure are likely to have contacts 

with diabetes and renal failure, such as other clients from the 

outpatient renal dialysis facilities they attend. Thus, when an 

outbreak involves cases with immunosuppression, it is even 

more important for public health investigators to quickly 

identify, assess, and when indicated, treat contacts.

Some ways to enhance the effectiveness of outbreak response 

involving immunosuppressed cases include

 Supporting urgent assessment of contacts at risk for 

immunosuppression by using incentives and enablers and 

providing on-site TB screening or access to health-care 

providers with extended hours of service;

 Providing LTBI treatment under DOT, ideally at settings 

frequented by contacts at risk for immunosuppression; and

 Considering presumptive treatment for TB disease or LTBI 

in contacts with severe immunosuppression.

Another important 

consideration 

when investigating 

outbreaks that involve 

immunosuppressed cases 

is that their contacts 

are also likely to be 

immunosuppressed.

Module 9—Tuberculosis Outbreak Detection and Response 

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Additional Resources

1. CDC. Best Practices for Genotyping-Based Tuberculosis 

Outbreak Detection. Atlanta, GA: Department of Health and 

Human Services, CDC; 2012. www.cdc.gov/tb/publications/

factsheets/statistics/Genotyping_BestPractices.pdf

2. CDC. Controlling Tuberculosis in the United States: 

Recommendations from the American Thoracic Society, CDC, 

and the Infectious Diseases Society of America. MMWR 2005; 54 

(No. RR-12). www.cdc.gov/mmwr/preview/mmwrhtml/rr5412a1.htm

3. CDC. Crisis and Emergency Risk Communication. Atlanta, GA: 

Department of Health and Human Services, CDC; 2012. 

https://emergency.cdc.gov/cerc/index.asp

4. 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

5. CDC. Prevention and Control of Tuberculosis in Correctional and 

Detention Facilities: Recommendations from CDC, 2006. MMWR 

2006; 55 (No. RR-09). www.cdc.gov/mmwr/preview/mmwrhtml/

rr5509a1.htm

6. Curry International TB Center. Model Tuberculosis Outbreak 

Response Plan for Low-Incidence Areas; 2006. http://www.

currytbcenter.ucsf.edu/products/view/model-tuberculosisoutbreak-response-plan-template-low-incidence-areas

7. National TB Controllers Association/CDC Advisory Group 

on Tuberculosis Genotyping. Guide to the Application of 

Genotyping to Tuberculosis Prevention and Control: Handbook 

for TB Controllers, Epidemiologists, Laboratorians, and Other 

Program Staff. Atlanta, GA: Department of Health and Human 

Services, CDC; 2004. www.cdc.gov/tb/programs/genotyping/

manual.htm

8. World Health Organization Stop TB Partnership. Working with 

the Media: How to Make Your Messages on Tuberculosis Count; 

2009. www.stoptb.org/assets/documents/resources/publications/

acsm/Working%20with%20the%20Media%20Final%20Web.pdf

Module 9—Tuberculosis Outbreak Detection and Response 

58
Answers to Study Questions

9.1 What is a TB outbreak? 

Generally, a TB outbreak is when there are more TB cases than expected within a 

geographic area or population during a particular time period, and there is evidence of 

recent transmission of M. tuberculosis among those cases.

9.2 What is TB outbreak response?

TB outbreak response is a process used by public health programs to investigate and 

intervene when a TB outbreak is suspected or confirmed. The ultimate goal of TB 

outbreak response is to interrupt ongoing transmission of M. tuberculosis.

9.3 What are three methods that health departments can use to detect TB outbreaks? 

Outbreaks can be detected through the following activities:

 Observations from health department staff and others in the community

 TB contact investigations

 TB case surveillance

 TB genotype surveillance

During these activities, health department workers should be alert for signs of more TB 

cases than expected and evidence of recent transmission among those cases.

9.4 List four circumstances when an increase in the number of TB cases may not 

represent an outbreak.

An increase in TB cases can happen for reasons other than an outbreak. Circumstances 

when an increase in the number of TB cases may not represent an outbreak include

 An influx of persons from areas where TB is more common (e.g., refugees)

 Persons are misdiagnosed with TB, as a result of mislabeling or contamination 

during specimen collection or in the laboratory (sometimes called false-positive 

laboratory results)

 Improved TB screening, diagnostic procedures, or reporting of cases (i.e., better 

case detection)

 A new clinician in a jurisdiction is more apt than predecessors to diagnose clinical TB

9.5 What is a genotype cluster?

A genotype cluster is when two or more cases have matching genotypes.

Module 9—Tuberculosis Outbreak Detection and Response 

59
Answers to Study Questions, Continued

9.6 What information is typically included in an outbreak case definition?

TB outbreak case definitions usually include the following four components:

1. TB genotype information (if available)

2. Characteristics about the affected persons (person)

3. Information about the location or place (place)

4. Time during which the outbreak occurred (time)

9.7 What is an outbreak line list? 

An outbreak line list is a summary of the cases that meet the outbreak case definition. 

In an outbreak line list, each row represents a different case. Each column contains key 

information on every case, such as

 Identifying Information

 Demographic Information

 Risk Factor Information

 Clinical and Laboratory Information

9.8 What is descriptive epidemiology?

Descriptive epidemiology is the aspect of epidemiology concerned with organizing 

and summarizing health-related data according to person, place, and time. Descriptive 

epidemiology is a way to characterize outbreaks.

9.9 What is a spot map?

A spot map is a technique for showing where cases might have been exposed to TB or 

where they might have exposed others after developing TB disease.

9.10 What are two ways investigators can characterize TB outbreaks by time?

Investigators can characterize TB outbreaks by time using 

 An epidemic curve (epi curve) 

 A plot of infectious periods

Module 9—Tuberculosis Outbreak Detection and Response 

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Answers to Study Questions, Continued

9.11 Why is it important to compile the individual contact investigation results for each 

outbreak case?

Compiling and analyzing contact investigation results can help focus initial outbreak 

investigative efforts on the most infectious cases. In addition, assessing the completeness 

of the initial contact investigations can help identify which cases may have had too few 

contacts identified during their contact investigation.

9.12 List five ways investigators can “fill information gaps” related to a TB outbreak.

Investigators can fill information gaps related to a TB outbreak in a number of ways, including

 Performing public record searches 

 Re-interviewing cases and contacts

 Repeating field visits and visiting new sites

 Updating clinical findings and laboratory results for cases and contacts

 Cross-matching the line list with homeless shelter and correctional facility records

9.13 List at least 5 activities health departments may need to implement to respond to 

an outbreak.

Activities that health departments may need to implement during TB outbreak response include 

 Extending hours of clinic services to accommodate the increased number of 

referrals, particularly for persons who are only available outside the health 

department’s usual hours of operation;

 Providing transportation for cases and contacts to the health department;

 Providing offsite services during nights and weekends;

 Providing DOT to a larger number of persons (e.g., not only cases, but also 

infected contacts at risk for rapid development of TB disease); and

 Offering incentives and enablers to accomplish active case-finding, contact 

assessment, and treatment completion goals.

Module 9—Tuberculosis Outbreak Detection and Response 

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Answers to Study Questions, Continued

9.14 What are some benefits of engaging stakeholders and partners in outbreak 

response efforts? 

Engaging with stakeholders and external partners enables public health investigators to

 Offer onsite education about TB;

 Access records at potential transmission sites; and

 Develop and deliver coordinated media messages that aid the investigation.

Such partnerships also help the health department gain important insight into the culture 

of persons involved in the outbreak and the barriers they may face in obtaining TB 

information, screening, and treatment.

9.15 What is the purpose of developing an outbreak summary?

The purposes of preparing the summary are to

 Ensure internal and external partners have updated information about the 

investigation and findings; and

 Provide recommendations for moving forward.

9.16 List at least two examples of longer-term outbreak response recommendations.

Longer-term outbreak response recommendations may outline

 Policies and procedures for improved TB prevention and control in settings and 

populations identified during the investigation as at risk;

 Post-outbreak genotype monitoring for the recurrence of the outbreak, such as 

with TB GIMS watch lists;

 Improved TB control program capacity and access to additional TB training for 

public health staff and community partners; and

 Program gaps that could be addressed to help prevent future outbreaks of TB.

Module 9—Tuberculosis Outbreak Detection and Response 

62
Answers to Study Questions, Continued

9.17 List the ten steps of the systematic approach to TB outbreak investigations.

Outbreak response generally includes the following 10 steps:

1. Confirm the existence of an outbreak

2. Define and list outbreak cases 

3. Examine existing information about outbreak cases

4. Convene the outbreak response team and develop the outbreak hypotheses 

5. Fill information gaps

6. Implement the specific outbreak response plan

7. Communicate interim findings

8. Summarize the outbreak response

9. Implement recommendations

10. Evaluate the outbreak response 

Module 9—Tuberculosis Outbreak Detection and Response 

63
Case Study Answers

9.1 Colin is an 8 month old child who was diagnosed with TB disease in Brown County. 

Typically, Brown County has less than two TB cases per year. The health department 

did a source case investigation and found that his mother, Kate, has latent TB 

infection and his Uncle Dave has TB disease. 

As an infant, Colin is unable to produce sputum, so the health department does not 

have a culture to submit for genotyping. However, the health department receives 

the results of Dave’s TB genotype and finds that it matches with two other recent 

cases from Brown County.

Would this lead you to suspect a potential TB outbreak? Why or why not?

A TB outbreak is when there are more TB cases than expected within a 

geographic area or population during a particular time period, and there is 

evidence of recent transmission of M. tuberculosis among those cases. In 

Brown County, it is possible there is a TB outbreak, because both of these 

criteria are occurring:

 More cases than expected—There are currently four diagnosed cases of TB 

in a county that usually experiences no more than two cases per year.

 Recent transmission—TB in children typically indicates recent transmission.

Additional investigation should be done to confirm the existence of the 

outbreak. For example, the health department should re-interview Dave and 

the other two cases to determine whether epi links can be established.

9.2 You are a health care worker at the local health department and have been assigned to 

investigate a TB outbreak. The TB genotype associated with this outbreak is G12345.

Using the line list below, determine if each case is a definite, probable, possible, 

or not an outbreak case. 

Case ID Age Gender Genotype Epi Linked to Other 

Outbreak Cases? Answer

TB291 35 M G12345 Yes Definite

TB302 75 F G98765 No Not an outbreak case

TB304 32 F Unknown Yes Probable

TB309 35 M G12345 Pending Possible

TB310 40 M G12345 Yes Definite

Module 9—Tuberculosis Outbreak Detection and Response 

64
Case Study Answers, Continued

9.3 Keith is a health care worker at the local health department, and he has been 

assigned to investigate a TB outbreak. Using the information from the outbreak line 

list he created an epi curve.

What does the shape of the epi curve tell Keith about the outbreak?

This epi curve shows that the outbreak has peaked and is in decline. This 

suggests that it is a “point source” outbreak and that the majority of the 

transmission occurred early in the outbreak.

9.4 You are a health care worker at the local health department and have been assigned 

to investigate a TB outbreak. Using the line list below, plot each case on the map at 

each location they have been connected to. 

Does it appear as though there are any locations where cases spent time together 

that may need further investigation?

For accessible explanation of map below, see Appendix for Accessibility on page 67.

There are several locations where cases spent time together: home 2, the 

homeless shelter, the jail, and the tavern. The health department should 

conduct a field visit to the homeless shelter. The health department may also 

want to assess home 2, the jail, and the tavern for additional contacts.

Module 9—Tuberculosis Outbreak Detection and Response 

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Case Study Answers, Continued

9.5 The health department in Purple County has been investigating and responding to 

an outbreak at a local factory. Eight employees have been diagnosed with TB disease. 

Most of the employees are foreign-born. The health department was initially alerted 

to the outbreak by an astute emergency room physician. 

Who are some potential stakeholders and partners the health department should 

reach out to?

Some stakeholders and partners that the Purple County health department 

may want to reach out to include:

 Cases, their family members, and their contacts 

 Hospital where the first case was diagnosed

 Factory management

 Community groups and organizations that provide services to this foreignborn population

 Public health officials from various agencies, such as CDC

Module 9—Tuberculosis Outbreak Detection and Response 

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Appendix For Accessibility

Figure 9.2: An example of a spot map. At the left of the map, 

there are 2 cases at a worksite. At the top, middle of the map 

there are four cases at a homeless shelter. At the center of the 

map there are three cases at Home 1. At the bottom, middle 

of the map there are two cases at Home 2. At the right, middle 

portion of the map there are three cases at a tavern. At the 

bottom, right side of the map there are two cases at a jail. 

Figure 9.3: The bar graph shows an example of a point source 

outbreak epi-curve from January 2011 to July 2013. There was 

a significant increase in July 2011, and cases decreased from 

January 2012 to July 2013. The epi curve has a steep up slope 

and a gradual down slope.

Figure 9.4: A bar graph showing an example of an ongoing 

outbreak epi-curve from January 2011 to July 2013. There was 

a gradual increase starting in January 2011, and a plateau from 

January 2013 to July 2013. The epi curve has a plateau, which 

indicates that the outbreak is ongoing. 

Figure 9.5: This horizontal bar graph shows an example of a 

plot of the infectious periods for cases involved in TB outbreak. 

Some cases had an overlap in infectious periods. 

 Case 1 had an infectious period of January 2012 to July 2012. 

 Case 2 shows an infectious period of around July 2012 to 

October 2012.

 Case 3 shows an infectious period of around October 2012 

to January 2013. 

 Case 4 shows an infectious period of around October 2012 

to April 2013.

Module 9—Tuberculosis Outbreak Detection and Response 

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Figure 9.6: This horizontal bar graph shows a plot of infectious 

periods with information from a spot map incorporated. Some 

cases had an overlap in infectious periods. 

 Case 1 had an infectious period of January 2012 to July 2012. 

Within this time frame, around April 2012, Case 1 spent time 

with Case 4 in jail. 

 Case 2 had an infectious period of around July 2012 to 

October 2012. 

 Case 3 had an infectious period of around October 2012 to 

January 2013. 

 Case 4 shows an infectious period of around October 2012 to 

April 2013. During this time, Case 4 stayed in Case 3’s home.

Case Study 9.3: This bar graph shows an epi curve for a TB 

outbreak. Cases remained consistent in January 2011 and July 

2011. There was an increase in cases in January 2012 and again 

in July 2012. Cases decreased in January 2013 and July 2013.

Case Study 9.4: A map that is labeled with locations where 

outbreak cases have spent time. On the left side, middle of the 

map, there is a worksite. At the top, middle of the map there 

is a homeless shelter. At the middle, center of the map there is 

Home 1. At the bottom, middle of the map there is Home 2. At 

the right, middle portion of the map there is a tavern. At the 

bottom, right side of the map there is a jail.

Case Study Answers 9.4: A map that is labeled with locations 

where outbreak cases have spent time. There are letters next to 

each location which are correct answers for case study question 

9.4. The work site is plotted with Case A. The homeless shelter 

is plotted with Case B, Case C, and Case F. Home 1 is plotted 

with Case A. Home 2 is plotted with Case D and Case F. The 

tavern is plotted with Case C and Case E. The jail is plotted with 

Case A and Case C.

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68
Notes

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Notes

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CS329840-A Publication Number 99-6206