METHODS: During a concurrent dengue/leptospirosis epidemic in Puerto Rico in 2010, suspected dengue patients that tested dengue-negative were tested for leptospirosis. Fatal and non-fatal hospitalized leptospirosis patients were matched 1:3 by age. Records from all medical visits were evaluated for factors associated with fatal outcome.
RESULTS: Among 175 leptospirosis patients identified (4.7 per 100,000 residents), 26 (15%) were fatal. Of these cases, only 59 (34%) were reported to passive surveillance, including two (8%) fatal cases. Most identified leptospirosis patients were older males and had illness onset during the second half of the year concomitant with the rainy season. Leptospirosis patients resided throughout the island in both urban and rural municipalities, and were most frequently either unemployed or agricultural workers. Following comparison of fatal cases and non-fatal controls, cases sought medical care earlier than controls (2.5 vs. 5 days post-illness onset [DPO], p < 0.01) and were more often diagnosed with leptospirosis at first medical visit (43.9% vs. 9.6%, p = 0.01). However, cases were admitted to the hospital no earlier than controls (4.5 vs. 6 DPO, p = 0.31). Cases less often developed fever (p = 0.03), but more often developed jaundice, edema, leg pain, hemoptysis, and had a seizure (p ≤ 0.03). Multivariable analysis of laboratory values from first medical visit associated with mortality included increased white blood cell (WBC) count with increased creatinine (p=0.001), and decreased bicarbonate with either increased WBC count, increased creatinine, or decreased platelet count (p<0.001).
CONCLUSIONS: This study revealed underreporting of leptospirosis in Puerto Rico that was particularly evident in fatal cases, emphasizing the need to improve case reporting to better enumerate burden of disease associated with this neglected tropical disease. Patients with fatal leptospirosis sought care earlier but were not admitted for care earlier than non-fatal cases. Because early initiation of leptospirosis-specific treatment has been associated with a survival benefit, combinations of routine laboratory values predictive of fatal outcome should be considered in admission decision-making for suspected leptospirosis patients.