Novel influenza A (H1N1) outbreak on board a US navy vessel

Abstract

Background and methods: Fleet Week New York 2009 was the latest installment of an annual celebration to honor US service personnel. It takes place during Memorial Day and this year's celebration coincided with the peak of novel influenza A (H1N1) virus (S-OIV) activity in New York City. Four service members from the USS Iwo Jima and USS Roosevelt contracted influenza while in New York City and were hospitalized in the Department of Veterans Affairs (VA)-New York Harbor Healthcare System to minimize the risk of widespread outbreak on board the naval vessels. No additional cases were identified on the USS Roosevelt. However, 135 service personnel on the USS Iwo Jima contracted influenza.

Results: Shipwide infection control measures including strict isolation and active case finding were instituted immediately with affected crew members and medical staff receiving oseltamivir. The new case rates remained high for 14 days, but the USS Iwo Jima was able to continue deployment. The secondary infectivity rate was 12.0%. The absolute end of the outbreak correlated with arrival at home port and the ability to move patients off board.

Conclusions: This outbreak not only reinforces the risk for rapid spread of novel strains of influenza A in confined populations but also demonstrates useful strategies to mitigate the severity of an outbreak, including isolation, infection control measures, and off board sick leave when feasible.