Arboviral Serology Testing

Arboviral serology testing is generally available from many commercial laboratories. As a result, the Michigan Department of Community Health's Bureau of Laboratories is no longer offering IgG testing of serum for routine diagnosis of WNV infection.

Patients presenting in the months of May-October with 1) viral encephalitis or meningitis, 2) Guillain-Barre syndrome, especially with atypical features, such as fever, altered mental status, and/or a pleocytosis and 3) febrile illness of sudden onset often accompanied by malaise, anorexia, nausea, vomiting, headache, myalgia, rash, lymphadenopathy and eye pain may need testing for arboviruses.

Cerebral spinal fluid (CSF): CSF is the preferred specimen for testing. The initial testing takes two days to perform. After an initial positive test in all the positive samples are repeated. A confirmed positive result is dispatched after repeat testing within 5 days of the receipt of the specimen. Please submit 2.5 ml of CSF for testing. IgM is performed several times per week as needed.

Serum: The presence of IgM antibodies in a single serum sample will not confirm a recent infection because IgM antibodies can persist in serum for up to 500 days post illness onset. Patients who have been recently vaccinated against or recently infected with related arboviruses (e.g., yellow fever, Japanese encephalitis, dengue, St. Louis encephalitis) or those who had a WNV infection in the previous year might have positive WNV IgM ELISA results that are unrelated to a recent illness. Therefore, patients being tested for WNV infection should submit a paired serum sample for examination.

Paired Serum samples: Both an acute serum sample drawn at least 8 days post onset of symptoms and a convalescent serum specimen drawn at least 22 days post onset should be submitted. In areas like Michigan where WNV has circulated in the recent past, testing of serially collected paired serum specimen is the only way to differentiate between a past and a recent infection. Such paired sera, which show a four-fold increase or a rising titers of IgG antibody enzyme-linked immunosorbent assay (IgG-ELISA) are indicative of a recent infection. Positive sera may be further tested by Plaque Reduction Neutralization Test (PRNT) to rule out the cross- reactions between WNV and other arbovirus infections (SLE, EEE and CGV). The results of this test are reported out as neutralizing antibody present or absent for the respective arbovirus. Please submit 2.5 ml of each serum for testing. Due to reductions in federal funding for WNV surveillance, IgG testing will not be performed at MDCH beginning in 2007.  All serum samples must be submitted to MDCH with a completed CDC form for forwarding and testing at CDC.

Specimen Submission: Submit specimens to the Michigan Department of Community Health (MDCH) via U.S. postal service, FedEx, UPS, or courier. Transportation may be at ambient temperatures. Submit specimens in plastic tubes only. Glass tubes are not accepted. For specific information on specimen submission, contact MDCH at 517-335-8063.