Recently, an extremely large number of ticks carrying the deer-tick virus (DTV) have been discovered in a recreational park in Pennsylvania. DTV, a variant of the Powassan virus, is transmitted through the bite of infected female black-legged ticks and can cause severe neurological complications such as encephalitis and meningitis. While many cases are asymptomatic, roughly 1 in 10 neuroinvasive cases are fatal, and about half of the survivors experience long-term neurological health impacts.
The virus is so dangerously lethal that it can be transmitted within 15 minutes of a tick bite. It is much faster than the time from bite and from bite to developing the infection for many other tick-borne diseases, such as Lyme disease. While the Powassan virus historically has been rare, annual cases of all tick-borne diseases reported to the CDC have more than doubled between 2004 and 2019, rising from over 22,000 in 2004 to more than 50,000 in 2019.
This increase in infection rates is likely due to the expansion of the black-legged tick, the vector for both the Powassan virus and Lyme disease. Increased temperatures and humidity are likely to contribute to increased reproduction, survival, and expansion of ticks, and climate change is expected to expand the range of black-legged ticks even further northward across the United States.
Changes in land use across North America, such as urbanization, have also played a role in the growth of the tick population, as deer and mice populations, which ticks use for blood meals, have increased in urban areas.
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