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BACKGROUND: A cluster of three locally-acquired dengue fever cases was reported by a local hospital in Martin County, Florida to the Florida Department of Health (FDOH) in August, 2013. Enhanced mosquito control efforts were implemented immediately. Active surveillance and outreach was initiated to identify additional cases, determine the extent of the outbreak, and to determine if transmission was continuing.
METHODS: All suspect cases were interviewed to obtain symptoms, date of onset, and recent travel history. Mosquito control officials were provided relevant information for surveillance and control efforts. Local physicians and medical facilities were reminded to report suspect cases of dengue fever to the appropriate county health department (CHD), and a CDC developed dengue training for physicians was provided in two hospitals. The public was encouraged to drain standing water from their property, take mosquito bite precautions, and report to their health care provider if they experienced a febrile illness. Outreach was also conducted with homeless persons in the impacted area. Suspect cases reported by the public directly to the CHD were directed to their health care provider if currently ill, or offered free dengue testing if the illness was resolved. In addition, a query was created to search the FDOH syndromic surveillance system (ESSENCE-FL) for discharge diagnoses and chief complaints consistent with dengue. A seroprevalence survey was also conducted in September. Serum samples from suspect cases were tested using dengue IgM and IgG enzyme-linked immunoassays (ELISA) and reverse transcriptase polymerase chain reaction (RT-PCR) assays as appropriate. All testing was performed at the FDOH Bureau of Public Health Laboratories.
RESULTS: In total 152 acute and convalescent serum samples from 139 suspect cases were tested with collection dates from 8/2/13 – 10/31/13. As a result, 22 cases with onset dates from 6/16/13 to 9/12/13 were identified. Ages ranged from 4 – 63 years; 41% of cases were female, 59% male. Fifteen cases were Martin County residents, five resided in other Florida Counties, and two were out-of-state visitors. All had outdoor exposure in at least one of two epicenters in the northern part of Martin County. One (4.5%) case was identified using the ESSENCE-FL query, one (4.5%) from the serosurvey, nine (41%) were hospital or physician reported, and 11 (50%) self/family-reported to the CHD.
CONCLUSIONS: Self/family-reporting identified the highest number of cases followed by hospital or physician reporting. Effective communication and outreach to local partners and the public were critical to successful outbreak surveillance and response.