Preliminary diagnosis 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 Ixodes species ticks.
Laboratory diagnosis is generally accomplished by testing of serum or cerebrospinal fluid (CSF) to detect Powassan virus-specific IgM and neutralizing antibodies. Immunoassays for Powassan virus IgM antibodies are available commercially and through state public health laboratories and CDC. Initial serological testing is performed using IgM capture enzyme-linked immunosorbent assay (ELISA). 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.
Molecular tests to detect viral RNA (e.g., reverse transcription-polymerase chain reaction [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.
Contact your state or local health department for assistance with diagnostic testing. They can assist you with determining if samples should be sent to the CDC Arbovirus Diagnostic Laboratory for further testing.
- Instructions for Submitting Diagnostic Specimens to the DVBD Arbovirus Diagnostic Laboratory
- CDC Data and Specimen Handling (DASH) Section Form 50.34 for Submission of Laboratory Specimens
ALL RESULTS WILL BE SENT TO THE APPROPRIATE STATE HEALTH DEPARTMENT. Specimens should be submitted to CDC through state health departments.