Investigation and response to a large outbreak of leptospirosis in Northern Sri Lanka

Introduction: Leptospirosis, a zoonotic bacterial disease, ranges from mild febrile illness to severe complications. Although Sri Lanka is endemic, Jaffna District was considered low risk. In November 2024, Cyclonic Storm Fengal caused flooding leading to an outbreak. An investigation was conducted to identify the causative agent and implement control measures. 
Objectives: To investigate an outbreak of an unidentified febrile illness following Cyclonic Storm Fengal in Jaffna District 
Methods: A rapid epidemiological investigation was launched following reports of fatalities and 40 suspected cases. Hospital records were reviewed and case definitions from national guidelines were applied. Laboratory testing, including polymerase chain reaction and microscopic agglutination test was conducted to confirm leptospirosis. Community outreach was implemented to identify additional cases. Veterinary testing of animal serum samples was also conducted to identify potential reservoirs. 
Results: A total of 104 suspected cases were identified during 1-17 December 2024, with 20 cases confirmed via laboratory testing. Males (70%) were predominantly affected, with the highest incidence among individuals aged 21-40 years. Seven fatalities occurred, primarily due to severe pulmonary haemorrhagic syndrome. Most cases originated from Point Pedro, Karaveddy and Chavakachcheri, areas with unhygienic livestock farming. Serological testing confirmed leptospirosis in cattle and goats, indicating zoonotic transmission. 
Conclusions & Recommendations: The outbreak highlighted the emerging risk of leptospirosis in Jaffna following extreme weather events. Strengthening surveillance, early diagnosis, and rapid treatment protocols are essential to reduce mortality. Public awareness campaigns and environmental sanitation measures, including livestock management, should be prioritized. Further research on the epidemiological shift in leptospirosis transmission in Northern Sri Lanka is warranted.