Sri Lanka chikungunya outbreak 2025
Sri Lanka health authorities are reporting a chikungunya outbreak in the country for the first time in 16 years.
A total of 173 chikungunya cases were reported from sentinel sites in Colombo, Gampaha and Kandy healthcare institutions (22 cases in November and December 2024, and 151 cases during 2025 as of the second week of March).
The highest case burden was observed in the 41–60 age group (40.5%) with a female predominance (60.2%).
Sri Lankan scientist Professor Neelika Malavige and her team carried out whole genomic sequencing of the currently circulating Chikungunya virus (CHIKV) strain and found that it was of the Indian ocean lineage (IOL), similar to the currently circulating CHIKV strains in South Asia.
While the E:226V mutation, which has been associated with Aedes albopictus transmission efficiency, was absent in all 2025 CHIKV viral sequences, they carried the E1:K211E and E2: V264A mutations, which result in enhanced viral fitness within the Aedes aegpti mosquito.
The mutations nsP1:I167V, nsP2:I171V, nsP2:T224I, nsP3:A382I and nsp4: were detected in the non-structural protein, with the Sri Lankan 2025 CHIKV strains showing unique mutations within nsP3:T224I and nsP4: S90A.
In Sri Lanka, the first chikungunya epidemic was reported in the early 1960s, followed by decades of quiescence. In 2006 Sri Lanka experienced a significant resurgence of chikungunya after several decades of epidemiological silence. Since then, intermittent cases and outbreaks have been reported, particularly in areas with high vector density. Between 2006 and 2007, an estimated 40,000 individuals were affected, with a similar number of cases recorded in 2008.
Chikungunya virus is transmitted to humans via the bite of an infected mosquito of the Aedes spp., predominantly Aedes aegypti and Aedes albopictus. Mosquitoes become infected when they feed on viremic humans or non-human primates, both of which are likely the main amplifying reservoirs of the virus. Humans are typically viremic shortly before and in the first 6 days of illness. While chikungunya is rarely fatal, studies have shown that 5% to 80% of patients with persistent joint pains and prolonged fatigue for months or years after illness.
CDC travel notice issued for countries in the Indian ocean region due to chikungunya