Travel Infections: In FoodNet data Campylobacter tops the list

By Lin H. Chen, MD, Assistant Clinical Professor, Harvard Medical School and Director, Travel Medicine Center, Mt. Auburn Hospital, Cambridge, MA

Dr. Chen has reviewed research grants from the Centers for Disease Control and Prevention and Xcellerex.

Synopsis: Travel was associated with 13% of the enteric infections reported to FoodNet, and the most commonly identified pathogens were Campylobacter, nontyphoidal Salmonella, and Shigella species. Precautions to avoid consuming contaminated food and water remains highly relevant in advising travelers.

Source: Kendall ME, et al. Travel-associated enteric infections diagnosed after return to the United States, Foodborne Diseases Active Surveillance Network (FoodNet), 2004-2009. Clin Infect Dis 2012;54(S5):S480-7.

FoodNet is an active surveillance program that collects data on 9 laboratory-confirmed pathogens from 10 sites in the United States: 7 states (Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, and Tennessee) and certain counties in California, Colorado, and New York. Kendall et al analyzed infections reported in this network from 2004-2009 that were considered to be travel-associated and compared them to infections in non-travelers; they also estimated risks according to travel destination. The authors defined travel associations based on the intervals between return date and illness onset: <30 days for Listeria, Salmonella (typhoid and paratyphoid), <15 days for Cryptosporidium and Cyclospora, and <7 days for all other enteric pathogens.

Approximately 13% (8270/64,039) of reported enteric infections that also contained travel information were considered travel-associated. Travel-associated cases had a mean age of 33.1 years, older than nontravelers (mean age 25.5 years), especially within the group aged 18-44 years. Travel-associated cases were more likely to be Asian, less likely to be black., and less likely to be hospitalized. Five deaths were reported for travel-associated cases, attributed to Listeria (n=1), Vibrio vulnificus (n=1), and nontyphoidal Salmonella (n=3).

The most frequently identified pathogens in travelers was Campylobacter (42%), followed by nontyphoidal Salmonella (32%) and Shigella infections(13%). These organisms were also the most common and top 3 for nontravelers, although nontyphoidal Salmonella was more common in nontravelers (47% of infections), and Campylobacter was less common (27% of infections). All 3 cases of cholera were travel-associated, as well as high proportions of typhoidal and paratyphoidal Salmonella (68% and 50%, respectively). Shigella dysenteriae, S. boydii, and S. flexneri were also often travel-associated (56%, 44%, and 24%, respectively), whereas non-cholera Vibrio, Yersinia, Shiga toxin-producing Escherichia coli (STEC), and Listeria occurred more commonly in nontravelers.

The most common countries for travel-associated infections were Mexico, India, Peru, Dominican Republic, and Jamaica, and account for half of the travel-associated cases. Furthermore, race and ethnicity correlated with travel destinations. For example, 85% of Asian travelers reported travel to Asia, 95% of Hispanic travelers reported travel to Latin America and the Caribbean [LAC], and 58% of black travelers reported travel to Africa.

The authors estimated risk for each pathogen based on travel region. Africa had the highest risk for travel-associated infection (76 cases/100,000 travelers), followed by Asia (23 cases/100,000 travelers), and LAC (20 cases/100,000 travelers). Within LAC, South America had the highest rate of Campylobacter (26.4 cases/100,000 travelers). The Caribbean had the highest rate of nontyphoidal Salmonella (8.6 cases/100,000 travelers), and Central America had the highest rates of Shigella, Cryptosporidium, and STEC.