Sri Lanka's dengue outbreak has grown from 25,082 cases in early May to 101,744 cases by October, with 78 deaths nationwide, according to National Dengue Control Unit (NDCU) figures published in an operational update by the International Federation of Red Cross and Red Crescent Societies (IFRC), posted on ReliefWeb on October 19.

The IFRC update, originally published on October 16, says heavy rains, the southwest monsoon and widespread flooding from mid-May 2026 led to the major outbreak. As of midnight on October 6, the NDCU had reported 101,744 cases and 78 deaths, a case fatality rate of 0.076 per cent.

The Western Province accounted for more than half of all reported cases, with 52,845 — mainly in Gampaha district (21,520) and Colombo district (19,879). The Southern Province reported 14,463 cases and the Central Province 9,580, the update says.

Cases peaked in July at 29,964, followed by 21,533 in June and 10,155 in August, before declining to 5,230 in September, the IFRC said. The July peak fits Sri Lanka's usual post-monsoon pattern, when accumulated rainwater creates favourable breeding conditions for Aedes mosquitoes. As of epidemiological week 37, 37 Medical Officer of Health areas remained classified as high-risk, and the NDCU identified seven provinces as high-risk, citing continued transmission linked to rainy conditions.

China's Xinhua news agency reported on September 29, citing Sri Lanka's Ministry of Health, that cases had already passed 100,000 with 77 deaths at that point. OneWorld SouthAsia reported on October 20 that tallies citing the NDCU put the count above 102,000 cases and 79 deaths by mid-October.

Health authorities have urged the public to eliminate mosquito breeding sites — including discarded containers and standing water around homes — and to maintain clean surroundings to slow the spread, according to Sri Lankan media reports citing the NDCU.

Sources: IFRC DREF Operational Update MDRLK024 (October 16, via ReliefWeb), Xinhua (September 29, via People's Daily Online), and OneWorld SouthAsia (October 20).