Diagnosis and Clinical Description of Leptospirosis Cases Identified Through Hospital-Based Active Surveillance in Puerto Rico, 2019-2021.

Leptospirosis is endemic to Puerto Rico, affecting people through seasonal increases and outbreaks. This report describes the diagnostic approach and clinical characteristics of leptospirosis cases identified through active undifferentiated acute febrile illness (UAFI) surveillance in Puerto Rico. From 2019 to 2021, active surveillance was conducted in four emergency departments (EDs), with standardized recruitment of patients aged ≥ 5 years, presenting with fever or a history of fever of unknown origin within the past two weeks. Additional cases were recruited from referrals of patients with positive leptospirosis diagnostic tests routinely ordered by clinicians. All enrolled patients were subject to a standardized diagnostic algorithm using PCR and serology to identify probable and confirmed leptospirosis cases. Patient data were collected from electronic medical records and interviews. Leptospirosis was diagnosed in 4% of 406 ED-enrolled UAFI patients, eight confirmed and eight probable cases. Referrals resulted in the identification of 12 routinely detected cases (five confirmed and seven probable). Of the 28 cases, 71% were ≤ 7 days post onset, 71% were male, average age was 43 years old, and the most common presentations included lower back pain (82%), headache (75%), fatigue (71%), vomiting (71%), myalgia (71%), and calf pain (64%). Common clinical laboratory findings were elevated AST (78%), hyperglycemia (74%), thrombocytopenia (48%), proteinuria (62%), and hematuria (62%). Classification of four isolates identified serovar Icterohaemorrhagiae/Copenhageni ( = 2), serovar Ballum/Guangdong, and (no serovar match). All but one of the leptospirosis cases met the current Council of State and Territorial Epidemiologists' definition for clinical compatibility with leptospirosis. Hemorrhagic symptoms and acute kidney injury with jaundice were associated with being a leptospirosis case. These findings underscore the role of leptospirosis among febrile illnesses in Puerto Rico, the need for increased awareness to optimize diagnosis and treatment, and further research to improve prevention and intervention strategies.