Powassa Ensephalitis is caused by a flavi virus, Powassan (POW), transmitted by the Ixodes cookei, Ixodes marxi, Ixodes spinipalpus, and Dermacentor andersoni ticks. May possibly be transmitted by Ixodes scapularis. Symptoms usually begin suddenly 7-14 days following infection, and include headache, fever, nausea and vomiting, stiff neck, and sleepiness. Later, breathing distress, tremors, confusion, seizures, coma, paralysis, and sometimes death can occur. 

The Ixodes scapularis (deer tick) transmits Powassan encephalitis.