Sri Lanka Dengue Outbreak 2026 – DREF Operational Update (MDRLK024), 16 October 2026

Please refer to the attached file. Description of the Event Date when the trigger was met 02-06-2026 What happened, where and when? Heavy rains, the southwest monsoon, and widespread flooding from mid-May 2026 led to a major dengue outbreak in Sri Lanka. Dengue cases increased from 25, 082 in early May to 101, 744 by October, representing almost a 600 per cent increase compared with the same period last year. The outbreak peaked in July 2026, when 29, 964 cases were reported. This July peak was consistent with Sri Lanka’s usual post-monsoon pattern, when accumulated rainwater creates favourable breeding conditions for Aedes mosquitoes. As of midnight on 6 October 2026, Sri Lanka’s National Dengue Control Unit (NDCU) had reported 101, 744 dengue cases and 78 deaths nationwide, with a case fatality rate (CFR) of 0. 076 per cent. The Western Province accounted for more than half of all reported cases, with 52, 845 cases, mainly in Gampaha (21, 520) and Colombo (19, 879) districts. The Southern Province reported 14, 463 cases (14. 21 per cent), while the Central Province reported 9, 580 cases (9. 41 per cent), making them the next most affected regions. Dengue cases peaked in July at 29, 964, followed by June with 21, 533 cases and August with 10, 155 cases, before declining significantly in September to 5, 230 cases. As of epidemiological week 37, 37 Medical Officer of Health (MOH) areas remained classified as high-risk, with an average midnight census of 451. The NDCU identified seven provinces as high-risk, citing continued transmission associated with rainy conditions favourable to mosquito breeding. Between August and the end of September, the geographic distribution of dengue cases shifted. Gampaha surpassed Colombo to become the most affected district, while the Western Province’s share of reported cases decreased slightly to approximately 52. 6–52. 8 per cent. Meanwhile, the Southern Province’s share increased to around 15. 6–15. 7 per cent, indicating a redistribution of cases rather than a uniform decline across the country. Overall, more than half of all dengue cases reported in 2026 were concentrated in the Western Province, consistent with historical patterns. Gampaha and Colombo districts continued to report the highest case numbers, underscoring the persistent challenge of vector control in densely populated areas. As of week 37, 36 Medical Officer of Health (MOH) areas remained classified as high-risk. The decline in cases observed in August is likely associated with the rapid rollout of the national “Stop Dengue Now” programme. SLRCS supported this effort through the DREF, working closely with MOH and NDCU officials at both Head Office and district levels. These efforts increased community awareness and strengthened targeted surveillance in high-risk areas. The campaign covered 14 districts and 72 Medical Officer of Health divisions and included enforcement measures, such as issuing “red notices” to properties where mosquito breeding sites were identified. A second seasonal increase related to the northeast monsoon remains possible. The 2026 case fatality rate of 0. 076 per cent reflects a long-term downward trend. Over the past two decades, Sri Lanka has reduced its dengue CFR, and maintaining a low fatality rate with more than 100, 000 reported cases reflects the continued capacity of the health system to manage severe dengue cases. The CFR of 0. 076 per cent is based on 78 reported deaths among 101, 744 reported cases. Gampaha and Colombo remained the main transmission centres, largely due to high population density and urban infrastructure, while Kandy was the most affected district outside the Western Province. Other districts with continued transmission included Matara, Kalutara, Galle, and Ratnapura. A notable development occurred in mid-July, when a cluster of 71 cases, including five hospitalizations, was identified among University of Colombo students. The University of Moratuwa and the University of the Visual and Performing Arts temporarily closed their campuses, marking the first institutional clusters recorded during this outbreak.

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