Clinical Testing and Diagnosis for Powassan Virus Disease

Considerations

Preliminary diagnosis of Powassan virus disease is based on the patient's clinical signs and symptoms, location where infection likely occurred (including places and dates of travel), and activities leading to risk of possible exposure to the virus primarily through Ixodes species ticks or rarely, blood transfusions.

Powassan virus disease is a nationally notifiable condition. All Powassan virus disease cases should be reported to local public health authorities. Reporting can assist local, state, and national authorities in recognizing outbreaks of this disease and instituting control measures to limit future infections.

Recommended tests

Laboratory diagnosis of Powassan virus infection is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect Powassan virus-specific IgM and neutralizing antibodies.

• Initial serological testing is performed using IgM capture enzyme-linked immunosorbent assay (ELISA). Powassan virus IgM testing is available commercially, at some state health departments, and at CDC.
• A positive Powassan virus IgM antibody test result should be confirmed by neutralizing antibody testing (plaque-reduction neutralization test [PRNT]) of serum specimens at a state public health laboratory or CDC.

Some patients who are immunocompromised might require molecular testing for diagnosis.

• Molecular tests to detect viral RNA (e.g., RT-PCR) can be performed on serum, CSF, and tissue specimens that are collected early in the course of illness and, if positive, can confirm an infection.
• Immunohistochemistry (IHC) can detect Powassan virus antigen in formalin-fixed tissue.
• Negative results of these tests do not rule out Powassan virus infection.
• RT-PCR and IHC is performed at CDC and some state public health or reference laboratories.

To submit specimens for testing, please contact your state or local health department. They can assist you with determining if samples should be sent to the CDC Arbovirus Diagnostic Laboratory for further testing. Specimens should be submitted to CDC through state health departments. All results will be sent from CDC to the appropriate state health department.