An outbreak of concurrent echovirus 30 and coxsackievirus A1 infections associated with sea swimming among a group of travelers to Mexico.

BACKGROUND: Enteroviruses are shed in human stool and can cause a wide spectrum of illness. They are the leading cause of aseptic meningitis.

METHODS: In 2004, the Connecticut Department of Public Health investigated a meningitis cluster among persons returning from a school-organized trip to Mexico.

RESULTS: Among 29 travelers (25 teenagers and 4 adult chaperones), 21 became acutely ill. Viral culture and nucleic acid amplification testing of stool (n=27) and cerebrospinal fluid (n=4) specimens identified enteroviral infection in 20 of 28 travelers from whom any specimen was obtained; 4 had echovirus 30 only, 11 had coxsackievirus (CV) A1 only, 4 had both echovirus 30 and CVA1, and 1 had CVA5 only. Illness onset dates were tightly clustered 4 days after a prolonged swim in the Gulf of Mexico. Time spent swimming was significantly associated with the odds of enteroviral infection (univariate odds ratio for each additional hour swimming, 14.3; 95% confidence interval, 1.3-154.3). Headache, fever, vomiting, and nausea occurred more frequently among the echovirus 30-infected travelers than among the uninfected control subjects (P< .05). The most frequent symptoms among travelers infected with only CVA1 identified were nausea and diarrhea (36% each), but neither was significantly associated with CVA1 infection; 5 patients with CVA1 infection were asymptomatic.

CONCLUSIONS: We identified multiple enteroviruses among the travelers. Clustered illness onsets suggest point-source exposure, which likely was a sea swim in sewage-contaminated seawater. Novel molecular amplification and sequencing methodologies were required to recognize the rarely identified CVA1, but it is ambiguous whether CVA1 infection caused illness. Travelers should be aware of risks associated with swimming in natural waters when visiting areas where there is limited sewage treatment.