Outbreak of 2009 pandemic influenza A (H1N1) on a Peruvian Navy ship - June-July 2009.

On June 25, 2009, a naval cadet reported to the infirmary of a 355-crewman Peruvian Navy ship with a febrile acute respiratory infection (FARI) 5 days after the ship docked in San Francisco, California. Pandemic 2009 influenza A (H1N1) virus was suspected as the cause because it was circulating in the city at that time. A test for pandemic H1N1 by real-time reverse transcription--polymerase chain reaction (rRT-PCR) was positive. During the subsequent 3 weeks, as the ship continued its cruise, 77 additional crew members developed confirmed pandemic H1N1 influenza. The U.S. Naval Medical Research Center Detachment (NMRCD), in collaboration with the Peruvian Navy, conducted an investigation to describe the outbreak and determine the attack rate for pandemic H1N1 influenza on the ship. This report summarizes the results of that investigation, which indicated that, of the 85 patients with FARI, 78 (92%) tested positive for pandemic H1N1 by rRT-PCR. The attack rate for confirmed pandemic H1N1 influenza was 22.0%. The most frequent symptoms, other than fever, were cough, headache, nasal congestion, and malaise. No complications or deaths occurred. Patients were treated according to World Health Organization (WHO) influenza treatment guidelines; six patients received antiviral medication because of preexisting comorbidities. A shipboard respiratory surveillance program, which had been implemented aboard the ship before its departure from Peru, permitted the early detection of the outbreak. Subsequent implementation of control measures might have slowed the outbreak. Laboratory disease surveillance and adequate outbreak control procedures might reduce transmission of pandemic H1N1 influenza aboard ships.