United States: Mosquito season is upon us, and with it comes the unwelcome arrival of diseases carried by these persistent insects to unexpected regions.
Communities in Massachusetts, New Hampshire, and Vermont are currently on high alert due to the emergence of a rare and deadly virus known as Eastern Equine Encephalitis (Triple E). Authorities have confirmed at least six cases, including one fatality, prompting officials to advise residents to remain indoors from dusk till dawn, the prime time for mosquito activity. In an effort to mitigate the threat, some towns have resorted to pesticide spraying.
Though limited in scope, the outbreak is alarming due to its severity. Approximately 30% of individuals who develop the acute form of Triple E succumb to the disease, and survivors often face lasting neurological impairments, according to data from the Centers for Disease Control and Prevention. There remains no vaccine or cure.
Over the past two decades, sporadic outbreaks have surfaced in the Northeast, with a record 38 cases reported in 2019 across the United States. Scientists are still grappling with the causes behind these outbreaks, with numerous environmental factors at play, including the bird species that transmit the virus to mosquitoes. Shannon LaDeau, a senior researcher at the Cary Institute of Ecosystem Studies, pointed to the escalating climate crisis as a significant contributing factor. As spring and autumn temperatures rise, mosquitoes are able to emerge earlier and persist later in the year while reproducing at an accelerated pace.
“Every aspect of mosquito development is expedited in warmer temperatures,” LaDeau explained. “The transition from egg to adult accelerates, and the virus inside the mosquito multiplies faster in heat. This results in a larger mosquito population and increases the likelihood of human interaction.”
Precipitation also plays a critical role, LaDeau noted. A warm spring in the Northeast was followed by substantial rainfall in early summer, fostering ideal conditions for an explosion of mosquito populations by late August.
These trends aren’t confined to the Northeast. Health experts have reported a rise in other mosquito-borne diseases across the United States and worldwide, driven by climate change, global travel, and trade.
Dr. Peter Hotez, dean of the National School of Tropical Medicine at Baylor College, voiced his concerns to PBS NewsHour about the growing number of vector-borne diseases — those spread by mosquitoes, ticks, and fleas — throughout the Western Hemisphere. Diseases such as Triple E, West Nile, and dengue fever are all on the rise.
In a disquieting development, the Oropouche virus, which typically circulates in South and Central America and the Caribbean, was detected this year in both the US and Europe for the first time. Meanwhile, yellow fever is encroaching on the outer reaches of the Amazon in Brazil.
“We are witnessing a broad uptick in vector-borne diseases across the hemisphere,” Hotez remarked. “Brazil and parts of the Caribbean are at the forefront, but we are also seeing an increase in cases across Texas and the Gulf Coast. This could very well become the new normal in the face of climate change, urbanization, and other evolving factors.”