Mosquito-associated Dengue Virus, Key West, Florida, USA, 2010

To the Editor: Except for sporadic cases along the Texas-Mexico border, local transmission of dengue virus (DENV) has not occurred in the contiguous United States since 1946. In 2009, DENV was diagnosed in a vacationer to Key West, Florida (1). Subsequently, 25 other cases were reported that year, transmission was confi rmed by detection of DENV serotype 1 (DENV-1) in local mosquitoes, and a random serosurvey showed evidence of recent DENV infection in 5.4% of Key West residents (1). Transmission continued in 2010, and an additional 63 cases were confi rmed (2). We used PCR amplifi cation and sequence analysis of virus identifi ed from mosquito collections during 2010 to identify the closest relatives, probable geographic origin, and divergence time of the Key West DENV. A total of 1,178 pools of Aedes aegypti mosquitoes were collected in Monroe County, Florida, during January 27-December 17, 2010 (online Appendix Figure, panel A, wwwnc.cdc.gov/EID/article/17/11/11-0419-FA1.htm), by using BG-Sentinel (Biogents, Regensburg, Germany) or CDC (Clarke, Roselle, IL, USA) light traps, and stored at -80C. Reverse transcription PCR was conducted on each pool by using primers designed to amplify all 4 DENV serotypes, followed by seminested PCR with serotypespecifi c primers (3). Results from 2 Key West mosquito pools collected on June 25 and 30 showed a positive fi rstround reverse transcription PCR and a positive second-round PCR specifi c for DENV-1. A third Key West pool collected on August 27 showed only a positive second-round PCR specifi c for DENV-1. No other DENV serotypes were detected.