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Effective TB Interviewing for Contact Investigation: Self-Study Modules

Return to Module 4 Table of Contents

Social Networks

Outbreak investigations may focus on congregate settings as sites for transmission. Investigations must also look at other common links between multiple index patients and places. The social network is a linkage of persons and places where M. tuberculosis is spread via shared air space. The analysis of the network can help identify important contacts, (i.e., those most likely to be infected). Social network analysis is best accomplished by someone who has access to multiple pieces of data collected in TB interviews of cases and contacts. Once links are established, including analysis of all priority contacts’ skin test results and medical examinations, additional interviews can be prioritized. For example, if a group of priority contacts were identified as having been exposed under similar circumstances, only a particular segment of the network may have skin test conversions. These contacts would be considered high priority for further, more extensive interviewing. In this situation, the re-interview should concentrate on any other exposure factors that may have caused additional risk for infection (e.g., substance abuse). In another example, a place where drug use takes place is an exposure environment. However, this environment is one that neither the contacts nor the index patient may mention during an interview. With further probing in a re-interview, this place may be mentioned if the contact realizes that the interviewer knows of the place and what occurs there.

Identifying Social Networks

Determining that M. tuberculosis has been transmitted to others can occur several months or longer after an index case is reported. The report of a case may be postponed due to a delay in seeking medical care until months after the patient becomes symptomatic. The interviewer should keep in mind the need to evaluate contacts exposed during the infectious period and all of the ways in which outbreaks can be uncovered. In this way, common exposure settings should be identified as follows:

  • Analyzing the data collection forms from various interviews should note common locations of exposure including work, school, and social settings. The data should also be analyzed for commonly named contacts (i.e., persons named by multiple cases). Actual names may not all be the same, as some patients may identify contacts by nicknames, a first name, or by physical description. Sort cases by first name and look for persons who may be mentioned several times (e.g., Dave, David, Davey or Rich, Richie, Ricco, Richard, Dick).
  • Re-interviewing the index case(s) involved and appropriate congregate setting personnel; if theindex case is deceased, an appropriate proxy should be identified.
  • Contacting other health departments from areas in which index cases, contacts, or both may spend time.

Further details can be noted and field visits made to common exposure sites. The field visits should be done per health department guidelines on congregate-setting investigations. However, if the congregate setting is social in nature, it may take the interviewer several visits to determine the pattern of social mixing, who frequents the setting, and who are the appropriate individuals from whom to gain additional information. Again, this process should be completed while only revealing the name of the index patient per health department standards of practice. In most cases, this is done when the patient’s identity will help to focus the investigation appropriately.

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