THURSDAY, March 29 (HealthDay News) -- Travelers returning to the United States imported 26 more cases of chikungunya fever in 2006, bringing known cases to an unprecedented 37 for the year, according to an update in the March 30 Morbidity and Mortality Weekly Report. Only seven confirmed cases were reported between 1991 and 2005, and only three of those were in travelers returning to the United States.
Chikungunya is an incurable mosquito-borne alphavirus suspected of infecting millions in the Indian Ocean region, causing fever, arthralgia and more rarely, death. Although the virus is not endemic to the United States, 12 imported cases were diagnosed in 2005 and early 2006.
The U.S. Centers for Disease Control and Prevention researchers confirmed 26 new cases via positive plaque-reduction neutralization and immunoglobulin tests and/or chikungunya virus isolation. The new cases were diagnosed in 17 states, and were imported by travelers in India (32), Sri Lanka (3), the Indian Ocean island of Reunion (1) and Zimbabwe (1). Because one-quarter of chikungunya infections are subclinical, local mosquitoes could spread the disease, the CDC cautions.
Travelers to affected regions should avoid mosquito bites, according to the report. "Persons with febrile illness suspected to be caused by chikungunya virus should avoid mosquito exposure for at least seven days after illness onset to reduce the likelihood of transmitting chikungunya virus to local mosquitoes," the authors write.
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