Tick-borne illnesses are on the rise, led by Lyme disease, which the CDC reports sickens at least 35,000 people annually. In the Northeast, black-legged ticks also carry the virus that causes Powassan encephalitis, a rare, serious illness that's on the rise in areas of New York state, according to new data. The illness, which has a 10% to 15% fatality rate, can cause central nervous system damage and long-term neurological damage. It's caused by Powassan virus and its deer tick virus variant. Mammals including raccoons and striped skunks were shown to transmit the pathogen to ticks.