Dengue virus immunoglobulin M detection in a reference laboratory setting during the 2010 dengue virus outbreak on Caribbean islands.

A large outbreak of dengue virus (DV) infections occurred on Caribbean islands during 2010, with cases peaking during the second half of the year. In conjunction with the outbreak, we observed an unprecedented spike in the number of sera submitted for DV antibody testing between June and December 2010, with a concomitant increase in the number of IgM-positive specimens, indicative of acute DV infection. Analysis of the place of residence of the IgM-positive patients identified from June to December of 2010 revealed that 58.1% were residents of Caribbean islands (Puerto Rico and the U.S. Virgin Islands), whereas 40.6% were residents of the U.S. mainland or Hawaii. The U.S. residents represented 42 states plus the District of Columbia, but most (53%) were from just 3 states (California, Florida, and New York). In comparison to the Caribbean IgM-positive patient group, the U.S. IgM-positive patient group contained proportionately more adults 21 to 60 years old and fewer individuals <21 years old. These findings indicate that the 2010 Caribbean DV outbreak affected many U.S. residents (mostly adults, presumably travelers) from diverse geographic areas and emphasize the potential for a viremic DV-infected returning traveler to spark a local DV outbreak by introducing DV into a community with competent mosquito vectors.