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Investigation Tools for Single Cases of Disease

Legionellosis case-patients should be interviewed to determine exposures during their incubation periods. This information helps detect both local and travel-related clusters and outbreaks, as well as informs national surveillance statistics, which are used in policy development. The following resources are provided to assist in the interview and investigation of single cases of disease.

Incubation Period Considerations

The incubation period is most commonly 2 to 10 days with an average of 5 to 6 days, but has been reported to be up to 19 days in rare cases. For routine surveillance purposes, exposure histories are collected for the 2 to 10 days prior to onset. However, in outbreak settings where it is important to consider a wide range of possible sources, use of a 14-day incubation period is often desirable.

Case Verification and Patient Interview Tools

  • Legionellosis Case Report Form [2 pages]
    Completed case report forms should be forwarded to CDC's Respiratory Diseases Branch Legionellosis Program within 7 days for travel-associated cases and within 30 days for non-travel cases. CDC Program staff will examine travel-associated reports for links to previously reported cases.
  • Hypothesis-Generating Questionnaire [6 pages]
    This form can be used to collect additional epidemiologic data after confirming a case of legionellosis and completing the CDC Legionellosis Case Report Form. These data may be useful in detecting outbreaks or in a future cluster or outbreak investigation. This form may be added to your state’s electronic notifiable disease surveillance system in whole or in part for routine data collection. A more detailed questionnaire that is customized to the outbreak location should be completed if the case is associated with a known outbreak.
  • Legionellosis Cruise Ship Questionnaire [6 pages]This form can be used to collect additional epidemiological data for cases that may be associated with a cruise ship. It should be completed after confirming a case of legionellosis and completing the CDC Legionellosis Case Report Form.

Information for Surveillance and Reporting

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