Pandemic influenza A(H1N1) outbreak among a group of medical students who traveled to the Dominican Republic.
BACKGROUND
From the beginning of the influenza pandemic until the time the outbreak described here was detected, 77,201 cases of pandemic influenza A(H1N1) with 332 deaths had been reported worldwide, mostly in the United States and Mexico. All of the cases reported in Spain until then had a recent history of travel to Mexico, the Dominican Republic, or Chile. We describe an outbreak of influenza among medical students who traveled from Spain to the Dominican Republic in June 2009.


METHODS
We collected diagnostic samples and clinical histories from consenting medical students who had traveled to the Dominican Republic and from their household contacts after their return to Spain.


RESULTS
Of 113 students on the trip, 62 (55%) developed symptoms; 39 (45%) of 86 students tested had laboratory evidence of influenza A(H1N1) infection. Most students developed symptoms either just before departure from the Dominican Republic or within days of returning to Spain. The estimated secondary attack rate of influenza-like illness among residential contacts of ill students after return to Spain was 2.1%.


CONCLUSIONS
The attack rate of influenza A(H1N1) can vary widely depending on the circumstances of exposure. We report a high attack rate among a group of traveling medical students but a much lower secondary attack rate among their contacts after return from the trip. These findings may aid the development of recommendations to prevent influenza.
Preventive Medicine and Epidemiology Department, Hospital Clinic, Barcelona, Spain.
Anna
A
Vilella
Beatriz
B
Serrano
Maria A
MA
Marcos
Anna
A
Serradesanferm
Josep
J
Mensa
Edward
E
Hayes
Andres
A
Anton
Jose
J
Rios
Tomas
T
Pumarola
Antoni
A
Trilla
D000328:Adult; D000401:Aircraft; D004196:Disease Outbreaks; D004293:Dominican Republic; D005260:Female; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics / Q000302:isolation & purification / Q000472:pathogenicity; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission; D008297:Male; D008875:Middle Aged; D058873:Pandemics; D060888:Real-Time Polymerase Chain Reaction; D013030:Spain / Q000453:epidemiology; D013337:Students, Medical / Q000706:statistics & numerical data*; D014195:Travel; D055815:Young Adult