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BACKGROUND: In December 2013, the first local transmission of chikungunya virus was reported in the Americas. Since then, the United States has seen an increase in chikungunya cases among travelers returning from endemic areas, particularly the Caribbean and South America. In June 2014, Florida reported the first local transmission of chikungunya virus in the continental United States.
METHODS: Cases were reported and interviewed by the Florida Department of Health; in addition to the initial interview, cases were interviewed for chronic symptoms three, six, and twelve months after onset as appropriate. The Council for State and Territorial Epidemiologists case definition for chikungunya virus was used to classify cases as either probable or confirmed. Surveillance related to local introductions of chikungunya virus included 50-100 meter cluster investigations around a patient’s residence, enhanced syndromic surveillance, and medical record review. Awareness was increased through media coverage, reverse 911 dialing, and targeted mailings.
RESULTS: Florida reported 11 locally-acquired and 435 imported chikungunya fever cases from January 1 to December 29, 2014. All 11 locally-acquired cases and 205 (47%) imported cases were confirmed, most by polymerase chain reaction (PCR). All 11 locally-acquired cases were Florida residents while imported cases included 404 Florida residents and 31 non-residents. Among imported cases, the most common reason for travel was to visit friends and relatives, reported by 285 (76%) of those responding. The most common country of exposure was Puerto Rico, reported by 114 (26%) patients, followed closely by Haiti, reported by 107 (25%) patients. The 11 locally-acquired cases were reported in four South Florida counties: one case in Broward, two cases in Miami-Dade, and four cases each in Palm Beach and St. Lucie. Three of these counties, Broward, Miami-Dade, and Palm Beach, have reported 203 (47%) of the 435 imported cases. Overall, the 446 cases reported in Florida were 59% female, 45% white, and 52% non-Hispanic. The median age was 50; 22% of cases were 65 or older and 8% were 18 or younger. Of the 349 cases with onset from January 1 to September 30, 2014, 217 could be contacted again for follow-up interviews; 92 (42%) of these cases were still experiencing symptoms three months after onset.
CONCLUSIONS: A large proportion of Florida’s chikungunya cases are still experiencing symptoms three months after infection. Awareness of the situation in Florida can help inform surveillance activities and control efforts throughout the United States.