Development of a Novel, Rapid, and Sensitive Immunochromatographic Strip Assay Specific for West Nile Virus (WNV) IgM and Testing of Its Diagnostic Accuracy in Patients Suspected of WNV Infection

Abstract

The West Nile virus (WNV), detected in the Western hemisphere in 1999, has since spread rapidly across North America into all 48 continental states of the US, 7 Canadian provinces, many Latin American countries, and throughout Mexico. More than 24 000 people in the US have tested positive for WNV infection; 9845 of these cases resulted in serious neuroinvasive disease and more than 959 were fatal (1). Guidelines for surveillance, prevention, and control of WNV are available(2). WNV, a member of the Flaviviridae family, belongs to the Japanese encephalitis serocomplex that includes Japanese encephalitis and St. Louis encephalitis viruses (3). WNV is transmitted to humans by mosquitoes. The transmission cycle involves mosquitoes and birds. In rare instances, the virus may be transmitted from human to human through organ donation or blood transfusion or from pregnant mother to fetus(4)(5)(6). WNV infections in a pediatric population have also been reported(7). Many patients remain asymptomatic or have only mild symptoms. Others report having fatigue, rash, fever, headache, and muscle weakness and may require hospitalization(8). The more severe form of the disease is meningoencephalitis manifested by typical signs of central nervous system infection and, in a minority of cases, development of a flaccid paralysis(9). Symptomatic patients will demonstrate an early antibody response of the IgM type during the 1st 4 days of illness, and nearly all patients will have detectable IgM antibodies by 7 to 8 days after the onset of illness (10). WNV-specific serum IgG is detectable by 3 weeks postinfection(11). The virus itself is usually no longer detectable by the time WNV-specific serum IgM appears, although both IgM and IgG may persist for more than a year(12). Laboratory-based ELISAs designed to detect WNV-specific IgM are now accepted as a …