UW News

July 10, 2003

Virology Division develops new assay for West Nile virus

Researchers and doctors in the Northwest who wonder if a blood or tissue sample has West Nile virus will no longer have to send samples to the East Coast for testing. The Virology Division of the UW Department of Laboratory Medicine has developed an assay to detect the virus.

This assay is based on the polymerase chain reaction (PCR) and can be used to detect West Nile virus in blood, cerebrospinal fluid, and other tissue or bodily fluids. The PCR assay is based upon detecting the virus’ 3′-UTR gene.

“This cutting-edge test will make it easier for people to detect the disease which, unfortunately, is expected to eventually reach the Northwest,” said Dr. Lawrence Corey, director of the UW Virology Division, professor of laboratory medicine and medicine and head of the Program in Infectious Diseases at the Fred Hutchinson Cancer Research Center.

In addition to the PCR assay, the Virology Division offers serologic testing to detect IgG and IgM antibodies to West Nile virus. These serological assays have been the most sensitive method for defining recent or past exposure. The assay uses sera from suspected patients to evaluate antibodies to the West Nile virus. The assay will detect cross-reactive antibodies to dengue and Japanese encephalitis virus and St. Louis encephalitis virus; hence results in persons exposed to such viruses either endemically or by vaccination may require interpretation, Corey said.

West Nile virus, a mosquito-borne flavivirus of the Japanese encephalitis serocomplex, is found in Africa, the Middle East, Southern Europe, parts of Asia, and now the United States. Although infection typically produces a mild dengue-like illness with low mortality, large outbreaks of severe neurological disease have occurred since 1994, apparently related to the emergence of a new genetic strain.

The virus has reached at least 44 states. Physicians and public health officials have already seen evidence of the spread of West Nile virus to the Pacific Northwest. These assays should help physicians make the diagnosis of West Nile infection. Currently, most physicians would have to send a sample to the Centers for Disease Control and Prevention, Corey said.

The test was developed at the Molecular Diagnostic Laboratory of the Division. The Virology Division of the UW School of Medicine was founded in 1968 and has been directed by Dr. Lawrence Corey since 1978. The Division’s mission is to provide diagnostic services and treatment for persons with viral diseases. The Division has research laboratories and clinics at Harborview Medical Center, UW, Children’s Hospital and Regional Medical Center, and the Seattle Cancer Care Alliance.

The West Nile virus assays were developed by faculty members affiliated with the Division, including Drs. Corey, Rhoda Ashley Morrow, Robert Coombs, Meei Li Huang, Keith Jerome and Linda Cook.