Legionnaires' Disease Surveillance

The Connecticut Department of Public Health (CT DPH) has conducted routine surveillance for legionellosis since 1997. Reported cases have generally increased over time, with annual and seasonal variation. CT DPH uses the national surveillance case definition to determine case status. Legionellosis is reportable to CT DPH by physicians and laboratories, and to the patient’s local health department. To help identify possible common sources of exposure, staff from the CT DPH Epidemiology and Emerging Infections Program and local health departments interview confirmed cases.

The figure shows reported legionellosis cases in Connecticut by month and year. Cases fluctuate from month to month, with higher counts generally occurring during warmer months. The data show seasonal variation and an overall pattern of continued legionellosis activity in Connecticut, supporting ongoing surveillance, case follow-up, and public health investigation of possible exposure sources.

 

 

Last updated 4/29/2026