Descriptive epidemiology of travel-associated diarrhea based on surveillance data at Narita International Airport

Although travelers' diarrhea is one of the most common health problems among international travelers, current findings depend largely on hospital and clinic-based information. To better understand the disease epidemiology and to identify specific subpopulations with increased risks, denominator data covering a large traveler population are needed.

We conducted a questionnaire survey of all travelers at the quarantine station, Narita International Airport, and retrospectively reviewed records from January 2001 to December 2005. The Immigration Bureau database was used as denominator data on travel patterns during the same period. To elucidate the risks of contracting diarrhea, we estimated incidence according to age, sex, month of travel, and travel destination.

A total of 7,937,654 people voluntarily submitted questionnaires; 9,836 had travelers' diarrhea. Travelers of both sexes aged 20 to 29 years reported the disease most frequently. Men aged 20 to 24 had the highest estimated incidence compared with any other age and sex group. The incidence was higher in March, August, and September than other months, mainly due to the influx of young adult travelers. Travel to south-central Asia, Southeast Asia, and North Africa was associated with higher risks than that to other areas.

Risks of contracting travelers' diarrhea are dependent on age, sex, season, and destination of travel. Incidence of diarrhea in all four seasons varies with age. Some destinations are associated with increased risks regardless of age. To prevent travelers from contracting diarrhea, adequate measures should focus on specific subpopulations.