Notes from the field: investigation of leptospirosis underreporting - Puerto Rico, 2010.

Leptospirosis, a zoonosis transmitted through contact with the urine of infected animals, either directly or through exposure to contaminated water or soil, is a frequent cause of acute febrile illness (AFI) and can be difficult to distinguish from dengue in areas where both are endemic. Approximately 5%-10% of patients with leptospirosis are affected severely; the case-fatality rate in those with severe disease is 5%-15%. Early identification of leptospirosis cases and early administration of penicillin G or doxycycline can reduce the duration and severity of illness.