Self-Study Modules on 

Tuberculosis, 6-9 

Module 9 

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
Module 9—Tuberculosis Outbreak Detection and Response

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Contents 

 Background

 Objectives

 New Terms

 Introduction to TB Outbreak Detection and Response

 Systematic Approach to TB Outbreak Response

 Special Circumstances in TB Outbreak Detection and Response

 Additional Resources

 Answers to Study Questions

 Case Study Answers
Module 9—Tuberculosis Outbreak Detection and Response

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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 list describe
Module 9—Tuberculosis Outbreak Detection and Response

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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 healthrelated 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

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

 
Module 9—Tuberculosis Outbreak Detection and Response

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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
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 

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. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

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An outbreak generally involves multiple TB cases with several 

overlapping contacts. 

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.

A quick and effective response to TB outbreaks can be a challenge for 

TB control programs even with substantial experience and resources. 

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 
Module 9—Tuberculosis Outbreak Detection and Response

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 Ensuring that staff are educated about proper infection control procedures

TB programs can improve their ability to respond to outbreaks by 

planning in advance how they will respond when an outbreak 

happens. 

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.

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-outbreakresponse-plan-template-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.

 
Module 9—Tuberculosis Outbreak Detection and Response

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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.

Health department workers should be alert for signs of more TB 

cases than expected and evidence of recent transmission among 

those cases. 

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 interferon-gamma release 

assay (IGRA) status from negative to positive 
Module 9—Tuberculosis Outbreak Detection and Response

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 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.

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 “pseudo-outbreaks.” 

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. 

 
Module 9—Tuberculosis Outbreak Detection and Response

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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 falsepositive 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 culture-positive 

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, 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).

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

happening.
Module 9—Tuberculosis Outbreak Detection and Response

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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 

Genotyping-Based Tuberculosis Outbreak Detection

(www.cdc.gov/tb/publications/factsheets/statistics/Genotyping_BestPractices.pdf).
Module 9—Tuberculosis Outbreak Detection and Response

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Study Questions 9.1 – 9.3 

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 67-71
Module 9—Tuberculosis Outbreak Detection and Response

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Study Questions 9.4 – 9.5 

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 67-71
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.

An important first step when determining whether there are more 

cases than expected is to verify the reported cases actually have TB 

disease. 

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 reinterviewing cases and conducting field visits.

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. 

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. 
Module 9—Tuberculosis Outbreak Detection and Response

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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).

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. 

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.

Genotyping information can be used to confirm epi links and may 

also identify previously unknown epi links. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

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Case Study 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? 

Answers to case studies are on pages 72-74
Module 9—Tuberculosis Outbreak Detection and Response

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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 are a standard set of criteria for 

deciding which TB cases could be involved in the outbreak. 

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)

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.

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.)
Module 9—Tuberculosis Outbreak Detection and Response

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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.

 

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).
Module 9—Tuberculosis Outbreak Detection and Response

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It is very important to apply the outbreak case definition in the same 

way to all cases being considered for inclusion in the investigation. 

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.

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.
Module 9—Tuberculosis Outbreak Detection and Response

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

outbreak case definition. 

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 27).

 

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.

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 
Module 9—Tuberculosis Outbreak Detection and Response

23

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

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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

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Study Questions 9.6-9.7 

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

 

 

 

 

 

 

 

9.7 What is TB outbreak line list? 

 

 

 

 

 

 

Answers to study questions are on pages 67-71
Module 9—Tuberculosis Outbreak Detection and Response

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Case Study 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 

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 72-74
Module 9—Tuberculosis Outbreak Detection and Response

27

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

Descriptive epidemiology characterizes outbreaks by person, place, 

and 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. 
Module 9—Tuberculosis Outbreak Detection and Response

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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”).

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.
Module 9—Tuberculosis Outbreak Detection and Response

29

Figure 9.2 Sample spot map. In this map, the pins represent outbreak cases. Each case 

is mapped to locations where they spent time.

 

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.

Important patterns often become visible when lines showing 

connections between the cases are added to the spot map or 

diagram. 

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. 
Module 9—Tuberculosis Outbreak Detection and Response

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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.

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. 

 

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

 
Module 9—Tuberculosis Outbreak Detection and Response

31

 

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

 

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 plot of the infectious periods shows the overall duration of the 

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

period. 

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. 

 
Module 9—Tuberculosis Outbreak Detection and Response

32

Figure 9.5 Plot of infectious periods for outbreak cases. 

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 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.
Module 9—Tuberculosis Outbreak Detection and Response

33

 

Figure 9.6 Plot of the infectious periods with information from the spot map 

incorporated.

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. 

Compiling and analyzing contact investigation results can help focus 

initial outbreak investigative efforts on the most infectious cases. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

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Study Questions 9.8-9.11 

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 67-71
Module 9—Tuberculosis Outbreak Detection and Response

35

Case Study 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 (below).

 

 

 

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

Answers to case studies are on pages 72-74
Module 9—Tuberculosis Outbreak Detection and Response

36

Case Study 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? 

 

 

 

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

 

Answers to case studies are on pages 72-74
Module 9—Tuberculosis Outbreak Detection and Response

37

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 manager should be identified. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

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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.

 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. 

Outbreak hypotheses are theories about how, when, and where TB 

transmission may have occurred during an outbreak. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

39

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.

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

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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.

The outbreak response team needs to confirm or collect new 

information based on the initial outbreak hypotheses. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

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Re-interviewing cases and contacts is essential for confirming 

information and for identifying locations, activities, or behaviors not 

discussed in earlier interviews. 

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 (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).

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). 

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 
Module 9—Tuberculosis Outbreak Detection and Response

42

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.

Any activities or locations identified by one case should be 

systematically incorporated into follow-up interviews with other 

outbreak cases. 

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 cross-matching 

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.

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.
Module 9—Tuberculosis Outbreak Detection and Response

43

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.)

 

Figure 9.8 Outbreak investigator conducting a repeat field visit.

 

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 
Module 9—Tuberculosis Outbreak Detection and Response

44

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 cross-matching by name.

Cases may not reliably self-report their homeless shelter stays or 

recent incarceration history. 

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.
Module 9—Tuberculosis Outbreak Detection and Response

45

Study Questions 9.12 

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

outbreak. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Answers to study questions are on pages 67-71
Module 9—Tuberculosis Outbreak Detection and Response

46

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.

The emphasis at this step shifts more to finding contacts, assessing 

them for TB infection and disease, and preventing additional 

outbreak cases. 

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 case-finding, 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

 
Module 9—Tuberculosis Outbreak Detection and Response

47

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.

Community partners (e.g., hospital infection control personnel, jail 

medical staff) can also become overwhelmed by the additional 

workload created by TB outbreaks. 

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 
Module 9—Tuberculosis Outbreak Detection and Response

48

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

territory.

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. 

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.

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.

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.
Module 9—Tuberculosis Outbreak Detection and Response

49

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.

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

50

Study Questions 9.13 

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 67-71
Module 9—Tuberculosis Outbreak Detection and Response

51

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. 

Effective outbreak responses require a high degree of collaboration 

among internal and external partners. 

Because TB outbreak response is such an intensive undertaking, health department 

staff may become so busy with the day-to-day 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.

 Having public information officers present at the first meeting of 

the outbreak response team 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;
Module 9—Tuberculosis Outbreak Detection and Response

52

 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

 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. 

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. 

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 
Module 9—Tuberculosis Outbreak Detection and Response

53

during outbreaks can help ensure it is accurate, helpful, culturally appropriate, and 

that it is coordinated with their own internal and external messages. 

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. 

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%20w

ith%20the%20Media%20Final%20Web.pdf

 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 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

54

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.
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Study Questions 9.14-9.15 

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 67-71
Module 9—Tuberculosis Outbreak Detection and Response

56

Case Study 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?

Answers to case studies are on pages 72-74
Module 9—Tuberculosis Outbreak Detection and Response

57

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.

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.

Recommendations are typically organized into immediate and longer 

term activities. Immediate recommendations usually emphasize the 

completion of TB prevention and control activities already underway. 

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 post-outbreak 

recommendations, phasing them in according to the capacity of their TB control 
Module 9—Tuberculosis Outbreak Detection and Response

58

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 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.

As recommendations are implemented, outcomes should be 

monitored and documented via progress reports or other methods. 

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.

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;
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 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

o Which areas of the TB control program are working well and which might 

be in need of improvement

o What barriers to outbreak detection or investigation were encountered

o How partnerships and collaboration strategies affected the effectiveness 

of the investigation

 What is left to be done 

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. 
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Study Questions 9.16-9.17 

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 67-71
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61

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 

o Inadequate isolation facilities, including lack of airborne infection 

isolation rooms 

o Recirculation of air from respiratory isolation rooms to other parts of the 

hospital 

o Failure to isolate patients until they are no longer infectious 

o Allowing isolated patients to leave their rooms without wearing a mask 

o 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.
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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.

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.
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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.

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.

Another important consideration when investigating outbreaks that 

involve immunosuppressed cases is that their contacts are also likely 

to be immunosuppressed. 

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
Module 9—Tuberculosis Outbreak Detection and Response

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 Considering presumptive treatment for TB disease or LTBI in contacts with 

severe immunosuppression.
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.pd

f

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
Module 9—Tuberculosis Outbreak Detection and Response

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8. World Health Organization Stop TB Partnership. Working with the Media: How to

Make Your Messages on Tuberculosis Count; 2009.

http://www.stoptb.org/assets/documents/resources/publications/acsm/Workin

g%20with%20the%20Media%20Final%20Web.pdf
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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 falsepositive laboratory results)

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

better case detection)
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 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.

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
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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.
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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.

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
Module 9—Tuberculosis Outbreak Detection and Response

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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

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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. 
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73

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 

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.
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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? 

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.

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