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Powassan (POWV) virus infection

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Powassan virus (POWV) infection is a rare tickborne arbovirus infection, transmitted by the bite of infected deer/blacklegged tick (Ixodes scapularis), the same tick that causes other tickborne diseases in Wisconsin, including Lyme disease. POWV is the only tickborne virus that is part of the arbovirus group (including West Nile virus) occurring in Wisconsin and other parts of North America (Maine, Michigan, Minnesota, New Jersey, New York, Vermont, and Canada). The presence of POWV has been documented in several ticks species (Ixodes spp., Dermacentor andersoni) and small and medium-sized mammal species (rodents, woodchucks, and skunks). The first case of Powassan identified in Wisconsin was in 2003.

People who are infected with POWV may experience a variety of symptoms from mild illnesses to lifeImage of a deer tick threatening complications; some people may not have any symptoms. Symptoms of illness usually begin 7-14 days (range 8-34 days) after being exposed to an infected tick bite. Signs and symptoms include acute onset of fever, muscle weakness, confusion, headache, nausea, vomiting, and stiff neck. Severe illness can include confusion, paralysis, speech difficulties, memory loss, and meningoencephalitis (inflammation of the brain and meninges).

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General information 

Data and statistics 

Graph of total cases of Powassan virus in Wisconsin from 2003 to 2013 by year of onset.

Information for health professionals

  • This is a Wisconsin disease surveillance category II disease: 
    Report to the patient's local public health department electronically, through the Wisconsin Electronic Disease Surveillance System (WEDSS), by mail or fax using an Acute and Communicable Disease case report F-44151 or by other means within 72 hours upon recognition of a case.
    Information on communicable disease reporting

  • Wisconsin case reporting and public health follow-up guidelines Arboviral diseases EpiNet

  • Wisconsin Arbovirus case report (PDF, 531 KB)

  • Laboratory Guidance
    • Because POWV is part of the arbovirus group, symptoms of Powassan virus infection are similar to other arboviral infections and can be difficult to differentiate. Blood tests can detect antibodies to POWV but are not readily available in commercial laboratories. However, testing can be requested through the Wisconsin State Laboratory of Hygiene for the arbovirus panel (West Nile, California/La Crosse, St. Louis, Eastern, and Western equine encephalitis virus) including Powassan virus testing. Confirmation for POWV will be performed at the Centers of Disease Control and Prevention (CDC).

      The Wisconsin State Laboratory of Hygiene (WSLH) performs arbovirus screening by a combination of tests including IgM capture enzyme immunoassays (IgM CEIA) and Microsphere Immunoassay for IgM antibodies performed on serum and cerebrospinal fluid (CSF). The WSLH will forward positive samples to CDC for confirmatory testing by Plaque Reduction Neutralization assay (PRNT). The WSLH offers arbovirus panel testing for fee-for-service. Meeting clinical criteria is not required to submit serum or CSF specimens to the WSLH for fee-for-service arboviral screening. 
    • The Wisconsin Division of Public Health (DPH) continues to monitor for POWV as part of our enhanced arbovirus surveillance. Testing for POWV as part of the DPH investigation may be fee-exempt. Please contact the Vectorborne Disease Epidemiologist at 608-267-0249 for fee-exempt approval.
  • Fee-exempt arboviral testing criteria   

    Fee-exempt testing for arbovirus infection including Powassan virus will be offered to clinicians whose patients meet one of the following criteria: 

    • Request for confirmatory testing of positive IgM and IgG commercial test results (performed at laboratories other than the WSLH)
    • POWV is the suspected agent causing illness and testing for other arboviruses (West Nile, California/La Crosse, St. Louis, Eastern equine, and Western equine encephalitis) demonstrated negative IgM antibody results
    • The patient has signs and symptoms of meningitis (fever, headache, and stiff neck) or encephalitis (fever, headache, and altered mental status ranging from confusion to coma), or acute flaccid paralysis (AFP) with no other laboratory diagnosis 
    • The patient has a diagnosis of Guillain-Barré syndrome and no other laboratory diagnosis
    • The local health department may request fee-exempt testing be performed if the case-patient lacks insurance coverage or the ability to pay.
  • Collection and shipping of clinical specimens to the WSLH 
    • Specimens submitted to the WSLH for fee-exempt testing must include the WSLH - Enhanced Wisconsin Arbovirus Surveillance Form provided by the Vectorborne Epidemiologist. 
    • Specimens submitted for fee-for-service testing must use the WSLH CDD Requisition Form B). Please contact the WSLH-Clinical Stock Orders, for ordering of kits and WSLH CDD Requisition Form B at 1-800-862-1088 or 608-265-2966.  
    • At least 3-7 mls of serum and/or >1ml of CSF in sterile screw-capped vials should be submitted on cold packs. 
    • It is essential that the lab requisition forms be as complete as possible including the patient name, city, date of birth, specimen type, submitting agency, onset date, signs and symptoms, and collection date.

Note: Testing for POWV may be delayed on specimens with laboratory forms missing the above requested data until information is available.


Wisconsin Local Health Departments - Regional offices - Tribal agencies

Diep Hoang Johnson Vectorborne Disease Epidemiologist
Wisconsin Division of Public Health 
Bureau of Communicable Diseases
(Phone 608-267-0249)  (Fax 608-261-4976)

Last Revised: August 20, 2014