Powassan virus disease is caused by a virus that reaches people mainly through the bite of an infected tick. The virus lives in nature by passing between ticks and animals, and people almost never pass it on — the rare exception is a blood transfusion.
The virus is found in the United States and parts of Russia.
The virus
Powassan virus is a tickborne flavivirus (genus Flavivirus, family Flaviviridae), related to tick-borne encephalitis virus of Europe and Asia. It comes in two lineages that are very similar but spread to people by different ticks:
- Lineage 1 — Powassan virus;
- Lineage 2 — deer tick virus.
How it spreads
- Ticks pick up the virus when they feed on groundhogs, squirrels, mice or other rodents with the virus in their blood.
- Infected ticks — Ixodes species — then pass it on when they bite people and animals.
- People are "dead-end" hosts: a tick that bites an infected person doesn't pick the virus up.
Powassan virus circulates between ticks and small rodents. CDC
It doesn't spread from person to person, except, rarely, through a blood transfusion. Anyone recently diagnosed with Powassan virus infection shouldn't donate blood or bone marrow for 120 days.
Which ticks carry it
Three kinds, found mostly in the eastern half of the United States:
| Tick | Bites people? |
|---|---|
| Ixodes cookei (groundhog tick) | rarely |
| Ixodes marxi (squirrel tick) | rarely |
| Ixodes scapularis (blacklegged or deer tick) | often — and it spreads several other diseases, including Lyme disease |
Prevention
There are no vaccines and no medicines to prevent Powassan. The best protection is to prevent tick bites.
Sources
Based on "Powassan: Causes and How It Spreads," Centers for Disease Control and Prevention; a work of the United States government in the public domain.
Licence: CC0 1.0 (public domain) · Adapted from www.cdc.gov
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