Everyone who spends time outdoors in the Northeast and Midwest in summer knows to check for ticks. The dominant worry is Lyme disease — and rightly so, given that an estimated 500,000 Americans contract it annually. But the same black-legged ticks (Ixodes scapularis) that transmit Borrelia burgdorferi also carry a virus that is, by many clinical measures, far more devastating: Powassan virus, a tick-borne flavivirus that causes brain infection, kills approximately one in ten people who develop neurological disease, and leaves approximately half of all survivors with permanent neurological damage.
And unlike Lyme disease — which requires the tick to be attached for 36 to 48 hours before the Borrelia bacteria can transmit — Powassan virus can be transmitted in as little as 15 minutes of tick attachment. Diligent tick checks after outdoor activity will not reliably prevent Powassan exposure. The tick that has been attached long enough to transmit the virus may still be small enough to miss on a body inspection.
