foodconsumer.org: Outbreak of 2009 Pandemic Influenza A (H1N1) on a Peruvian Navy Ship

Outbreak of 2009 Pandemic Influenza A (H1N1) on a Peruvian Navy Ship
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admin on 02/24/2010 23:27:00
 
OUTBREAK OF 2009 PANDEMIC INFLUENZA A (H1N1) ON A PERUVIAN NAVY SHIP ---
JUNE--JULY 2009
WEEKLY
February 19, 2010 / 59(06);162-165
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.
Since 2002, the Peruvian Navy training ship ATC 131 has been making trips with
second and fourth-year Peruvian Navy cadets visiting many ports of the world. In
May 2009, the ship cruised from Peru to San Francisco via Ecuador and Costa
Rica, stopped in San Francisco, (docked in port during June 20--24), and
returned to Peru via Mexico (July 1--5) and Panama (July 10--12). In each port,
the crew went ashore for protocol or visiting activities. Before the ship
departed Peru, the crowded living conditions and difficulties in maintaining
hygiene aboard ship prompted the Peruvian Navy to implement a respiratory
surveillance program. Health personnel were trained on FARI diagnosis (oral
temperature ≥100.5°F [≥38.1°C] and cough or sore throat) and respiratory
swab specimen collection techniques. In addition, crew members were encouraged
to seek medical attention through the ship's infirmary as soon as they developed
signs or symptoms of respiratory illness (e.g., fever, cough, or sore throat).
Personnel were provided with personal protective equipment (PPE) and were
trained in proper respiratory hygiene.
Six weeks after departure, on June 25, 2009, 1 day after the ship set sail from
San Francisco, one crew member reported to the infirmary with a 2-day history of
fever of 101.3°F (38.5°C), sore throat, nasal congestion, headache, malaise,
and cough after at least a 1-day visit ashore in San Francisco. After undergoing
a negative rapid influenza test, the patient was discharged from the infirmary
with symptomatic treatment but was not placed in isolation. Two days later, on
June 27, another crew member reported to the infirmary with similar symptoms
that had begun 1 day before, including a temperature of 102.9°F (39.4°C);
however, he tested positive for influenza A with the rapid test. This second
patient shared living quarters with the first patient. The first patient was
then retested with a rapid test and was found to be positive for influenza A
(Figure).† The two patients were placed in isolation and given symptomatic
medication. This incident alerted the staff on board to a possible pandemic H1N1
outbreak.
During June 28--July 4, during the stopover in Mexico, 33 additional crew
members reported to the infirmary with FARI symptoms. The first six underwent
respiratory swab testing, and all six swabs tested positive for pandemic H1N1
using rRT-PCR by local health port authorities in Mexico. The other patients
were presumed to have pandemic H1N1 infection. A case definition was then
instituted. A case of pandemic H1N1 influenza was defined as illness in a person
with FARI symptoms and laboratory-confirmed H1N1 infection by rRT-PCR. All
respiratory swab samples from patients with FARI symptoms were then tested for
pandemic H1N1 influenza by rRT-PCR and viral isolation at NMRCD after the ship
had returned to Peru on July 17.
All subsequent patients with FARI symptoms had specimens tested for pandemic
H1N1 influenza by rRT-PCR and viral isolation. The specimens were stored frozen
in liquid nitrogen (at approximately -180ºC) until they were tested at NMRCD
after the ship returned to Peru on July 17.
During July 5--11, an additional 41 crew members reported to the infirmary with
FARI symptoms. An additional deck, adjacent to the infirmary, was made available
for patient isolation. Patients were isolated for a minimum of 7 days (range:
7--9 days) or until symptoms resolved. All patients were given masks to help
prevent them from spreading the virus to susceptible persons and were required
to wear the mask for at least 5 days after discharge from the isolation
facility. In addition to being recommended water and soap hygiene, all patients
were provided with alcohol-based hand gel sanitizers to help reduce respiratory
illness transmission (1). All remaining crew members were actively screened
daily for FARI through a clinician-patient interview and by taking their oral
temperatures; those who had at least one respiratory symptom were placed in
isolation, given hand sanitizers and masks, and were monitored daily for
additional symptoms. Upon docking in Panama on July 10, all onboard personnel
were re-instructed in proper respiratory hygiene and given additional PPE. The
following week, after departing from Panama, nine additional FARI cases were
detected. The last case detected on the ship was in a patient who reported to
the infirmary on July 16. All respiratory swab samples were stored in liquid
nitrogen in the infirmary until they could be tested later at NMRCD
laboratories.
Among 355 crew members, a total of 78 cases of pandemic H1N1 were confirmed by
rRT-PCR. The attack rate was 22.0% (78 of 355) (Table). Respiratory swab
specimens from seven patients with FARI tested negative for pandemic H1N1 by
rRT-PCR. Attack rates varied by rank and age group (p