BACKGROUND: Leptospirosis is an acute febrile illness caused by infection with Leptospira species, a bacteria increasingly prevalent in Louisiana deer and feral swine. Infected animals can transmit Leptospira species to humans through urine-contaminated water, often during flooding. In August 2016, Louisiana experienced widespread flooding; hospital laboratories subsequently reported 2 initial leptospirosis cases in patients with flood-water exposure. We investigated to determine the burden of flood-related leptospirosis in Louisiana.
METHODS: We queried the Louisiana Early Events Detection System (LEEDS), a state-wide syndromic surveillance system, to identify patients with chief complaints or diagnoses clinically compatible with leptospirosis from flooded areas from 2 days after flooding onset to 30 days after water recession. We performed medical record reviews and applied the Council of State and Territorial Epidemiologists’ (CSTE) case definition; patients with laboratory evidence supporting an alternate diagnosis were excluded. Patients were interviewed to determine floodwater exposure. Blood and urine specimens were tested for leptospirosis with polymerase chain reaction (PCR); serum was tested by microscopic agglutination test (MAT) for initial cases and patients from LEEDS with floodwater exposure.
RESULTS: LEEDS query yielded 69 patients warranting medical record review. Of 18 patients meeting the CSTE case definition, 13 were interviewed; 4 reported floodwater exposure and submitted blood and urine specimens; however, MAT and PCR were negative for Leptospira infection. Both initial cases were confirmed by MAT; urine PCR in 1 case identified Leptospira kirschneri as the infecting species.
CONCLUSIONS: No additional confirmed cases of postflooding leptospirosis were identified. However, Leptospira species endemicity in Louisiana wildlife and 2 laboratory-confirmed cases of leptospirosis postflooding warrants a high index of suspicion for leptospirosis in patients with compatible symptoms and exposure to untreated water, especially during flooding.