Epidemiology and Infection

Gastrointestinal infection

Multi-pathogen waterborne disease outbreak associated with a dinner cruise on Lake Michigan

F. SERDAREVICa1a2, R. C. JONESa1, K. N. WEAVERa1, S. R. BLACKa1, K. A. RITGERa1, F. GUICHARDa3, P. DOMBROSKIa4, B. P. EMANUELa5, L. MILLERa1 and S. I. GERBERa6 c1

a1 Communicable Disease Program, Chicago Department of Public Health, Chicago, IL, USA

a2 Epidemic Intelligence Service, Centers for Disease Control and Prevention, Atlanta, GA, USA

a3 Food Protection Division, Chicago Department of Public Health, Chicago, IL, USA

a4 Division of Laboratories, Illinois Department of Public Health, Springfield, IL, USA

a5 Consumer Safety Division, Food and Drug Administration, Chicago, IL, USA

a6 Communicable Disease Program, Cook County Department of Public Health, Oak Forest, IL, USA

SUMMARY

We report an outbreak associated with a dinner cruise on Lake Michigan. This took place on the same day as heavy rainfall, which resulted in 42·4 billion liters of rainwater and storm runoff containing highly diluted sewage being released into the lake. Of 72 cruise participants, 41 (57%) reported gastroenteritis. Stool specimens were positive for Shigella sonnei (n=3), Giardia (n=3), and Cryptosporidium (n=2). Ice consumption was associated with illness (risk ratio 2·2, P=0·011). S. sonnei was isolated from a swab obtained from the one of the boat's ice bins. Environmental inspection revealed conditions and equipment that could have contributed to lake water contaminating the hose used to load potable water onto the boat. Knowledge of water holding and distribution systems on boats, and of potential risks associated with flooding and the release of diluted sewage into large bodies of water, is crucial for public health guidance regarding recreational cruises.

(Accepted April 27 2011)

(Online publication May 19 2011)

Correspondence:

c1 Author for correspondence: S. I. Gerber, M.D., Cook County Department of Public Health, 15900 S. Cicero Avenue, Bldg. E-3rd Fl., Oak Forest, IL 60452, USA. (Email: sgerber@ccdph.net)

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