What Is Powassan Virus?

Powassan virus (POWV) is a flavivirus that is part of the tick-borne encephalitis (TBE) complex, a group of enveloped, non-segmented, positive-sensed single-stranded RNA viruses (1). There are two lineages of POWV that have been found, lineage I and linage II with distinct transmission cycles. Both lineages have been linked to human disease. POWV lineage II is a transmitted by Ixodes scapularis ticks (deer ticks), and cases of POWV caused by POWV lineage II are increasing in North America (1-3) POWV infection is characterized by syndromes of fever, headache, and altered consciousness and in some cases, neuroinvasive symptoms are present (2,4). About 10% of POWV encephalitis is fatal, and 50% of POWV survivors have permanent neurologic problems (5).

In addition to clinical symptoms, serological testing can be used to support the diagnosis of POWV.  Isolation and detection of POWV RNA from blood and cerebrospinal fluid (CSF) can be used as diagnostic tools early in infection prior to seroconversion (5). However, as hospitalization and subsequent testing usually occurs after POWV has been cleared from CSF and blood, diagnosis is then based on detection of IgM and IgG antibodies. IgM and IgG antibodies against POWV are detected in serum/plasma using an ELISA (5). A positive IgM antibody test can be confirmed by >90% or >50% plaque reduction neutralization test (PRNT90 or PRNT50), which provide quantification of the antibody titers (7).

Powassan is endemic in the northeast and upper Midwest of the United States where the seroprevalence in humans ranges from 0.5%–3.3% in some regions.(6) It has been reported that 7% of adult ticks carry the virus in POWV-endemic regions. With the expanding territory of I. scapularis and significant increases in the number of Powassan cases in the last decade, there is an urgent need for methods to detect POWV.

Our Speakers

How Is Powassan Virus Detected?

DATE: DECEMBER 14th, 2021    |   TIME: 11:00 AM EDT

Dr. Ciota is Director of the Arbovirus Laboratory, which performs clinical testing, surveillance, and research of arthropod-borne viruses (arboviruses). The lab studies both mosquito and tick-borne agents including the flaviviruses West Nile virus (WNV), dengue virus, Zika virus and Powassan virus, as well as alphaviruses including eastern equine encephalitis virus and Mayaro virus, among others. The unique facilities which comprise the Arbovirus lab allow for extensive experimentation in a range of natural invertebrate and vertebrate hosts. Dr. Ciota’s primary research areas include arbovirus evolution, mosquito-virus interactions, and the role of temperature in arbovirus transmission.

Dr. Wolf earned her PhD in Immunology & Microbiology at the University of Colorado. After her research post-doctoral fellowship at North Carolina State, she started her career in the field of Public Health Lab with an emerging Infectious Diseases Post-Doctoral Fellowship at the North Carolina State Laboratory of Public Health.  Dr. Wolf served as Public Health Scientist, Assistant Public Health Laboratory Director and finally Public Health Laboratory Director until moving back to Kentucky.  In December 2016, she became Laboratory Director and Clinical Assistant Professor in the Division of Infectious Diseases, Department of Medicine at the University of Louisville (UofL).  Three years ago, she became an Adjunct Professor in the UofL School of Public Health and Information Sciences, teaching undergraduate Public Health majors and mentoring Master of Public Health Students to help train the next generation of public health professionals. Dr. Wolf has authored over 50 publications in peer-reviewed journals and her goal is to better understand emerging tick-borne diseases.

How do people get infected with Powassan virus?

Powassan virus is spread to people primarily by infected ticks.

Transmission occurs 15 minutes after tick attachment (8)

When is the risk of Powassan infection highest?

POWV season is during late spring, early summer and mid-fall (9)

How is Powassan virus treated?

Currently there is no treatment for the virus, only supportive care (10)

How can I reduce the chance of getting infected with Powassan virus?

The best way to prevent POWV disease is to protect yourself from tick bites by:
     1) Avoiding tall grass and overgrown areas
     2) Wearing long sleeves, long pants tucked into socks, & shoes
     3) Using insect repellent
     4) Performing tick checks after coming in from the outdoors (11)

Frequently Asked Questions


1.         Dupuis AP, 2nd, Peters RJ, Prusinski MA, Falco RC, Ostfeld RS, Kramer LD. Isolation of deer tick virus (Powassan virus, lineage II) from Ixodes scapularis and detection of                        antibody in vertebrate hosts sampled in the Hudson Valley, New York State. Parasit Vectors. 2013;6:185-185.
2.         Piantadosi A, Rubin DB, McQuillen DP, et al. Emerging Cases of Powassan Virus Encephalitis in New England: Clinical Presentation, Imaging, and Review of the Literature. 
            Clin Infect Dis. 2016;62(6):707-713.

3.         Powassan (POW) Virus Disease Fact Sheet. https://www.health.ny.gov/diseases/communicable/powassan/fact_sheet.htm. Published 2021.
4.         Neitzel DF, Lynfield R, Smith K. Powassan virus encephalitis, Minnesota, USA. Emerg Infect Dis. 2013;19(4):686-686.
5.         Hermance ME, Thangamani S. Powassan Virus: An Emerging Arbovirus of Public Health Concern in North America. Vector Borne Zoonotic Dis. 2017;17(7):453-462.
6.         Frost H, Schotthoefer A, Thomm A, et al. Serologic Evidence of Powassan Virus Infection in Patients with Suspected Lyme Disease. Emerging Infectious Disease                                          journal. 2017;23(8):1384.
7.         Diagnostic Testing | Powassan | CDC. https://www.cdc.gov/powassan/diagnostic-testing.html. Published 2021. Updated 2021-06-23T09:12:05Z.
8.         Ebel GD, Kramer LD. Short report: duration of tick attachment required for transmission of powassan virus by deer ticks. Am J Trop Med Hyg. 2004;71(3):268-271.
9.         Statistics & Maps | Powassan | CDC. https://www.cdc.gov/powassan/statistics.html. Published 2021. Updated 2021-06-23T09:05:57Z. 
10.       Symptoms, Diagnosis, and Treatment | Powassan | CDC. https://www.cdc.gov/powassan/symptoms.html. Published 2021. Updated 2021-08-20T05:34:32Z. 
11.       Cdcgov. Preventing tick bites | Ticks | CDC. @CDCgov. https://www.cdc.gov/ticks/avoid/on_people.html. Published 2020. Updated 2020-07-01T01:58:08Z.

DATE: DECEMBER 14th, 2021    |   TIME: 11:00 AM EDT