Concord, New Hampshire – The United States has reported its first death this year from the rare mosquito-borne eastern equine encephalitis virus (EEEV), also known as “Triple E”. The recent fatality, confirmed in New Hampshire, marked the state’s first human case in a decade and the fifth case of the virus in the country in 2024.
The EEEV, which attacks the central nervous system and can lead to brain inflammation or swelling, has a history of impacting the eastern and Gulf Coast states of the US. Human cases are primarily prevalent in these regions, where a complex ecosystem involving various bird species and mosquitoes dependent on arboreal swamps for breeding facilitates the virus’s spread.
Although the virus circulates among birds in hardwood swamps, it is transmitted to humans and mammals by mosquitoes that serve as carriers. Infected humans and horses are considered as “dead-end hosts” since they do not contain enough virus in their blood to transmit EEEV back to mosquitoes. As a result, the primary carriers of the virus, such as the black-tailed mosquito, are critical in the spread of EEEV during the mosquito season, typically from summer to autumn in the US.
The symptoms of EEEV in humans can include sudden fever, chills, headaches, vomiting, and seizures, with severe cases resulting in brain swelling. Despite its rarity, EEEV remains a serious concern for public health authorities due to its impact on the brain and a mortality rate of 30 percent. Prevention strategies, such as using insect repellents, mosquito control programs, and wearing protective clothing during peak mosquito hours, are recommended to reduce the risk of infection.
Climate change is also believed to play a role in the spread of EEEV, as warming temperatures and increased humidity can prolong the mosquito season, creating favorable conditions for the virus to thrive. Although experts caution about the impact of climate change on the prevalence of mosquito-borne diseases, this year’s cases are deemed part of the normal dynamics of EEEV transmission.
As authorities implement control measures and urge the public to take precautions, the recent death in New Hampshire serves as a stark reminder of the potential dangers associated with mosquito-borne viruses like EEEV. With continued vigilance and proactive measures, efforts to mitigate the spread of such diseases remain ongoing across the United States.