The disease is transmitted by two types of mosquitoes. The first is a species called Melon-like Culisetaor black-tailed mosquito. This mosquito tends to live in hardwood swamps and feeds on birds such as robins, herons, and wrens, spreading the virus among them. But the melanura mosquito does not typically bite mammals. A different species of mosquito, Coquillettidia perturbansThe mosquito is primarily responsible for most of the human cases of the disease reported in the U.S. The perturbans mosquito acquires the EEE virus when it feeds on birds and then infects the humans and horses it bites. Toward the end of summer, when mosquitoes have reached their peak numbers and begin to vie for any available blood meals, human cases begin to appear.
Andreadis, who published a historical retrospective On the progression of triple E in the northeastern United States in 2021, he said climate change has emerged as a major driver of the disease.
“We have milder winters, warmer summers and extreme rainfall and drought conditions,” he said. “The impact that this has on mosquito populations is probably quite profound.”
Warmer global average temperatures generally produce more mosquitoes, regardless of species.
Studies have shown that warmer air temperatures up to a certain threshold, around 90 degrees Fahrenheit, shorten the time it takes C. melanura The eggs hatch. Higher temperatures in spring and fall extend the number of days mosquitoes have to breed and feed. And they will feed more often in summer if it’s warmer (mosquitoes are ectothermic, meaning their metabolism speeds up in higher temperatures).
Rainfall also influences mosquito reproduction and activity, as mosquito eggs need water to hatch. A warmer atmosphere retains more moisturewhich means that even small amounts of rainfall produce more water today than they did a century ago. The more standing water there is in roadside ditches, abandoned car tires, ponds, swamps and potholes, the more opportunities mosquitoes have to breed. And warmer water reduces the incubation period for mosquitoes. C. melanura eggs, leader A study to conclude that warmer-than-average water temperatures “increase the likelihood of EEE amplification.”
