West Nile Virus: An Emerging Virus in North America

Extract

West Nile virus is an emerging virus that first appeared in North America during the summer of 1999 in New York City. There were seven deaths associated with this event. Surveillance reports indicate that the virus had been spreading south and west and in 2002, had been reported in 42 states and the District of Columbia. As of September 2002, there were 2121 total human cases reported, including 104 deaths. The fatality rate for the West Nile virus is very low and the majority of individuals will have no clinical symptoms; however, individuals at most risk for more serious form of the disease are the elderly, the immunocompromised, and young individuals. The virus is spread by certain mosquito species and certain populations of birds serve as the reservoir hosts. Because person-to-person transmission does not occur, humans are therefore considered dead-end hosts. Confirmation of cases West Nile virus infections in humans are determined based on clinical and laboratory findings.

West Nile virus (WNV) was first isolated in 1937 from the blood of an ill woman in the West Nile region of Uganda. The original investigators noted at the time that the virus caused encephalitis in rhesus monkeys. During the next 15 years, the disease was found to be endemic in Egypt and had caused sporadic summertime epidemics in Israel. In the 1950s, attack rates in Israel were at times greater than 60%. Since, infection has been found in Africa, the Middle East, parts of Europe, the Indian subcontinent, and the former…

ABBREVIATIONS: CDC = Centers for Disease and Control; CSF = cerebrospinal fluid; EEE = Eastern Equine Encephalomyelitis; ELISA = enzyme-linked-immunosorbent assay; PCR = Polymerase Chain Reaction; PRNT = plaque reduction neutralization test; VEE = Venezuelan equine encephalitis; SLE = St Louis encephalitis; WNV = West Nile virus