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Identify and Report Travel-associated Legionellosis

cruise ship

Outbreaks are commonly associated with buildings or structures that have complex water systems, like cruise ships.

Travel has been reported during the incubation period for approximately 10% of legionellosis cases reported to CDC. Since travelers typically disperse from the source of infection before developing symptoms, detection of travel-associated clusters can be challenging. If reported in a timely fashion, individual cases associated with travel to hotels or aboard cruise ships can help to detect clusters and outbreaks.

Legionellosis case-patients should be interviewed if possible to determine detailed travel exposures, and state health departments should notify CDC of all travel-associated cases. CDC assists with travel-associated cluster detection because national-level surveillance is necessary to detect outbreaks due to the multi-state nature of travel in the United States. Surveillance through the National Notifiable Diseases Surveillance System (NNDSS) is also important for monitoring national trends; all cases should also be reported through NNDSS.

The Council of State and Territorial Epidemiologists (CSTE) adopted a position statement in 2005 to strengthen surveillance for travel-associated legionellosis. The CSTE position statement also includes revised case definitions for legionellosis.


How to Report Travel-associated Cases

Reporting travel-associated cases involves two steps:

  1. Email to let CDC know about travel-associated cases of Legionnaires’ disease within 7 days.
  2. Continue official notification mechanisms through NNDSS and through submission of case report forms [2 pages].

CDC will notify the state health departments where the patient traveled.


Authority over Cruise Ships

The Respiratory Diseases Branch works closely with the Vessel Sanitation Program and the Division of Global Migration and Quarantine to investigate cases of disease associated with cruise ship travel.


  1. Hicks LA, Garrison LE, Nelson GE, et al. Legionellosis — United States, 2000–2009. MMWR Morb Mortal Wkly Rep. 2011;60(32):1083–6.

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