First Isolation of West Nile Virus from a Patient With Encephalitis in the United States

Cinnia Huang, Brett Slater, Robert Rudd, Nandakishore Parchuri, Rene Hull, Michelle Dupuis, Alexander Hindenburg


Emerging Infectious Diseases. 2002;8(12) 

In This Article

Abstract and Introduction

West Nile virus (WNV) was isolated from a patient who developed encephalitis while undergoing treatment with CHOP (cyclophosphamide, hydroxydoxorubicin, vincristine [Oncovin], predisone) and rituximab for a non-Hodgkin B-cell lymphoma. Both standard reverse transcription-polymerase chain reaction (RT-PCR) and Taqman RT-PCR established the diagnosis of WNV infection from cerebrospinal fluid (CSF). Several whole blood samples and one serum sample underwent further testing. CSF and serum samples were negative for WNV antibody; however, all samples were positive by both RT-PCR assays. Infectious virus was recovered from a blood sample, and its identity was confirmed by using a WNV-specific immunofluorescence assay. The complete WNV genomes determined from CSF and from the virus isolate adapted from cell culture were the same. The results represent the first complete WNV genome sequence obtained directly from human CSF and the first time that infectious WNV has been recovered from a patient with encephalitis in North America.

West Nile virus (WNV), an arthropod-borne virus, is a member of the Japanese encephalitis virus serocomplex of the genus Flavivirus, family Flaviviridae[1], discovered in Uganda in 1937[2]. Although WNV infections are usually mild or asymptomatic, in some instances, a severe and fatal encephalitis is produced, typically in the elderly[3]. This virus was first recognized in the Western Hemisphere in an outbreak in New York in 1999[4]. As of October 2, 2002, a total of 2,671 cases of human illness in the United States have been reported to the Centers for Disease Control and Prevention (CDC). Although WNV has been recovered from mosquitoes, birds, and horses, no isolations from humans have been reported in the Western Hemisphere. Thus, all prior data regarding the virus responsible for human illness in North America have come from nucleic acid sequencing of the viral genome in either cerebrospinal fluid (CSF) or brain tissue. We describe the first isolation of WNV from a human case-patient associated with the U.S. outbreak. Because the virus was also directly detected by reverse transcription-polymerase chain reaction (RT-PCR) in specimens from the same patient, we were able to compare the entire genomic sequence of the directly detected virus with that of the cell-culture isolate.