Powassan case raises awareness of potentially fatal disease
Powassan (POW) virus is an arbovirus transmitted to humans by the deer tick, also a known carrier of Lyme disease. It can infect the central nervous system, and may cause inflammation of the brain (encephalitis) and the membranes that surround the brain and spinal cord (meningitis). Approximately 10 percent of POW virus encephalitis cases are fatal, and an estimated 50 percent of survivors have permanent neurological symptoms, according to the CDC.
The MMWR reports that the Connecticut patient survived.
Approximately 75 cases of POW virus disease were documented in the United States in the past 10 years, with 47 of those cases reported in the last 5 years. Most cases occur in the Northeast and Great Lakes regions in the late spring, early summer and mid-fall when ticks are most active. Based on the latest CDC stats, 2006-2015, more than half of the cases also were reported in the northern counties of Minnesota and Wisconsin. No cases have ever been confirmed in Iowa.
The onset of mosquito-borne arboviruses in patients usually occurs from June through August. Infected ticks, though, can be active well before and well after peak mosquito season. Onset in the Connecticut patient happened in November.
Patients who have the POW virus disease may not have any symptoms or could have a range of symptoms, including fever, headache, vomiting, weakness, confusion, loss of coordination, speech difficulties, seizures and encephalitis. There is no specific treatment other than supportive therapy. The virus is rapidly transmitted from tick exposure in as little as 15 minutes compared to the estimated 24 to 48 hours for Lyme disease transmission.
Preliminary diagnosis is often based on the patient's clinical features and activities, and the epidemiologic history of the location where infection occurred. Laboratory diagnosis is generally accomplished by testing serum or cerebrospinal fluid to detect virus-specific IgM and neutralizing antibodies.
More information is on the CDC’s Powassan virus website.
