Guide to the Application of Genotyping to Tuberculosis Prevention and Control

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Appendix B: References and Useful Resources

Core Steps of an Outbreak Investigation

  1. Confirm that it meets epidemiologic definition of an outbreak (any one of the following)
    1. More cases than expected (surveillance)
    2. Cases epidemiologically clustered by time, space, or common behaviors
  2. Consider whether there is ongoing transmission (one of the following)
    1. Did regular contact investigations reveal epidemiologic links or similarities among cases?
    2. Did the laboratory identify a genotyping cluster that confirms the epidemiologic links identified by regular contact investigation?
    3. Did the laboratory identify a genotyping or epidemiologic cluster of lab isolates clustered in time and space where there is discordance between the clinical course of the patient and the laboratory results (false-positive culture)?
  3. Define an outbreak-related case
  4. Confirm existing number of outbreak-related cases
  5. Investigate existing outbreak-related cases by reviewing
    1. Medical records (history, physical, clinical chart, and notes)
    2. Laboratory records (serial results of smears, cultures, drug sensitivities, and other testing)
    3. Review genotyping results for all culture-positive cases (if not already done, submit isolates for genotyping)
      1. If lab results are implausible and the clinical course of the patient does not support TB diagnosis or the clinician does not think that there is concordance between lab results and clinical course of the patient to support TB diagnosis, consider possibility of false-positive cultures
    4. Chest radiographs (including old baseline films, if possible)
    5. Tuberculosis clinic and other pertinent public health records
    6. Cross match outbreak-related cases with county jail, state prison, and STD registries
    7. All data from regularly conducted contact investigations (re-interview case-patients and their contacts as necessary)
  6. Determine the infectious period for each outbreak-related case based on
    1. Laboratory results (e.g., sputum smear-positive patients are thought to be more infectious)
    2. Serial chest radiographs (e.g., patients with cavitary lung lesions are thought to be more infectious)
    3. Date of onset and duration of signs and symptoms
    4. Results of screening of named contacts (e.g., a high percentage of TST-positive contacts)
  7. Determine the sites and facilities frequented and family and social groups exposed by outbreak-related patients during their infectious periods
    1. Information from case-patient interviews and contact investigations
    2. Information from medical and public health records
    3. Information from the facility logs or records
  8. Determine the exposed cohort of persons at each site/facility who may have been present when an outbreak-related case-patient was present during his/her infectious period
    1. Information from case-patient interviews and contact investigations
    2. Information from medical and public health records
    3. Information from the facility logs or records
  9. Determine the duration by number of hours, days, or weeks. for the exposed cohort of persons who may have spent around an infectious outbreak-related patient
    1. Information from case-patient interviews and contact investigations
    2. Information from medical and public health records
    3. Information from the facility logs or records
  10. Prioritize exposed cohorts for screening (active case finding and latent TB infection) based on:
    1. Type (e.g., indoor versus outdoor, intimate versus casual), frequency, and duration of exposure
    2. Risk of progression to active disease
  11. Define elements of and action plan for screening, implementation, and follow-up
  12. Identify resources necessary for action plan to be carried out
  13. Create a media plan to respond to possible inquiries
  14. Assign responsibilities and set deadlines
  15. If necessary, expand screening to include low-priority cohorts after screening high-priority cohorts based on evidence of transmission
  16. Evaluate, treat, and follow up additional TB disease case-patients and latent TB infected persons associated with this outbreak
  17. Make and implement recommendations to prevent future outbreaks for particular populations or settings involved
  18. Evaluate outbreak response
  19. Determine whether interventions have effectively stopped TB transmission in this situation.
  20. Identify the lessons learned that could improve the public health response to the next outbreak.