Why in news?
Health officials in Nassau County, New York reported a locally acquired case of chikungunya virus infection in September 2025. It is the first known instance of local transmission in the United States since 2019. The patient had not travelled abroad, indicating that infected mosquitoes in the area had picked up the virus from an earlier traveller.
Background
Chikungunya is a mosquito‑borne viral disease first identified in Tanzania in the 1950s. It is caused by the chikungunya virus, a member of the alphavirus genus. The virus is primarily transmitted to humans by Aedes mosquitoes – Aedes aegypti and Aedes albopictus – which bite during the day. Outbreaks have occurred across Africa, Asia and the Americas, typically in tropical and subtropical climates.
Symptoms and transmission
- Clinical presentation: Infected individuals usually develop symptoms 3–7 days after a bite. The disease is characterised by sudden high fever, severe joint pain (often in the hands and feet), muscle pain, headache, nausea, fatigue and rash. Though most patients recover within a week, joint pain can persist for months.
- Groups at risk: Serious complications are uncommon but may occur in newborns, older adults and people with underlying medical conditions. Chikungunya is rarely fatal.
- Mode of transmission: The virus spreads when a mosquito bites an infected person and later bites another person. Unlike malaria, there is no human‑to‑human transmission without the mosquito vector. There is currently no licensed vaccine; treatment focuses on relieving symptoms.
Context of the U.S. case
- Local transmission: The Nassau County case likely resulted from a local mosquito biting a traveller who returned with the virus and then transmitting it to another person. Previous U.S. outbreaks occurred in 2014 in Florida.
- Low risk in temperate regions: Cooler nights in the northeastern United States reduce mosquito survival, so widespread outbreaks are unlikely. Nevertheless, climate change and global travel have expanded the range of Aedes mosquitoes.
- Prevention measures: Health authorities advise residents to use insect repellent, wear long sleeves, empty standing water containers and ensure screens on windows and doors to prevent mosquito bites.
Conclusion
The isolated chikungunya case in New York serves as a reminder that global viruses can resurface when conditions permit. Vigilant mosquito control, public awareness and research into vaccines remain key to preventing larger outbreaks.
Source: Financial Express · CDC