Sri Lanka: Dengue Outbreak - May 2026

Dengue cases have been on the rise in the country since the beginning of the year. Following a massive seasonal surge triggered by heavy rains in mid-May 2026, the epidemic trajectory accelerated significantly. Driven by the onset of the southwest monsoon and severe local flooding, the island-wide total quickly advanced from 25,082 cases in early May to more than 35,000 cases by the first week of June, marking an approximate 30% increase compared to the corresponding period of the previous year (as noted by reports via Dengue Visual Atlas).

A higher number of cases is recorded in the Western, Southern, North Western, Sabaragamuwa, and Central provinces, especially in the Colombo, Gampaha, Kalutara, Kandy, Galle, Matara, and Ratnapura districts. The National Dengue Control Unit (NDCU) reported more than 8,600 new cases of dengue virus within the month of May 2026 alone, raising grave concerns about a potential epidemic. The NDCU also revealed that environmental conditions following high rainfall and major urban flooding are rapidly accelerating the spread of the virus across the country. As of 8 June 2026, a total of nearly 37,000 dengue cases have been recorded across the island, according to data highlighted by NDCU.

Almost 50 per cent of the above-mentioned cases were reported from the Western Province. Indeed, Colombo District recorded the highest number of dengue infections island-wide, accounting for 55.1% of all reported cases nationwide. During week 22, as per the NDCU update, the Colombo District reported a high number of cases (550), followed by Gampaha (531) and Kalutara (265). Outside the Western Province, substantial case numbers were reported from Matara (194), Kandy (173), Ratnapura (160), Galle (142), Hambantota (69), Kurunegala (68), and Kegalle (68), indicating widespread transmission across multiple provinces. ([IFRC, 20 Jun 2026](https://reliefweb.int/node/4217159))

During the 26th week, 6009 suspected dengue cases were reported across all 26 d