Diseases are riding ticks and mosquitoes to new pastures. Lyme disease and West Nile virus are among the ailments that ticks and mosquitoes are spreading in more of the U.S. Reported infections after tick, flea, and mosquito bites have surged over the past two decades, according to data from the Centers for Disease Control and Prevention.

According to the WSJ, Changing land use and climate have allowed ticks to expand their habitat. Warming temperatures can encourage mosquito-borne outbreaks, and more global travel risks moving the bugs and their diseases to new areas. That can challenge doctors and communities unaccustomed to dealing with these diseases.

Lyme disease is the most common tick or mosquito–borne disease in the U.S. It is most prevalent in the Northeast and Midwest, where the black-legged tick that carries Lyme-causing bacteria has expanded its range, leading to more infections.


West Nile virus and other mosquito-related infections spread cyclically but unpredictably, in part because of the mosquito’s short lifespan.

According to LiveMint, The virus first appeared in the U.S. in New York City in 1999 and reached most of the country within five years. It is now the leading cause of mosquito-borne illness in the continental U.S.

The razing and regrowth of forests in the Northeast have facilitated a boom in the deer population, which has brought black-legged ticks back with them. White-footed mice also host Lyme-causing bacteria.

Building homes and infrastructure deeper into the woods can increase the chances people encounter ticks, and shorter, warmer winters are lengthening the time the ticks are active and allowing them to move north.

The spread of the West Nile virus often relies on infected migrating birds. There also tend to be more outbreaks when it’s warmer, partly because the virus can replicate faster within the mosquitoes and make them infectious earlier.