Serological Evidence of Ongoing Transmission of Dengue Virus in Permanent Residents of Key West, Florida

Introduction: Dengue fever is the most important mosquito-borne viral disease in the world, with 40% of the global population at risk of infection. Dengue virus is responsible for infections in over 100 countries, including the Americas and Caribbean Basin; however, it has been largely eradicated from the United States through the implementation of effective vector control programs. However, between 2009 and 2010, 27 permanent residents of Key West, Florida, were reported to have locally acquired infections, marking the first autochthonous cases detected in Florida since 1934. Despite this recent and unusual transmission, and the potential risk of serious illness associated with sequential infections, no active surveillance had been conducted since. Materials and Methods: A serosurvey of permanent residents of Key West, Florida, was conducted in March of 2012. After informed consent, enrolled participants (n=173) were given a dengue virus rapid diagnostic test and completed a corresponding questionnaire. Results: The presence of immunoglobulin G (IgG) antibodies was indicated in 12 participants (6.9%), all of whom reported travel to endemic countries within the past 2 years. Surprisingly, six participants (3.5%) without any recent travel outside the state of Florida gave positive results for IgM antibodies. The presence of birdbaths and bromeliads on the property and sleeping outdoors emerged as significant factors related to previous exposure, whereas home air conditioning without the use of open windows and the use of mosquito repellent were protective. Conclusions: These findings suggest local transmission occurred in Key West in early 2012, indicating that transmission may not have subsided in 2010.