Epidemic West Nile encephalitis, New York, 1999: results of a household-based seroepidemiological survey

Cost-effectiveness of West Nile Virus Vaccination

“…The highest seroprevalence published to date is 2.6% ( 1 ). In 2002, during the largest epidemic of WNV neuroinvasive disease ever described in the United States, 2,942 neuroinvasive WNV disease cases were reported from 36 states and the District of Columbia (total population ≈253.4 million).…”

“…In 2002, during the largest epidemic of WNV neuroinvasive disease ever described in the United States, 2,942 neuroinvasive WNV disease cases were reported from 36 states and the District of Columbia (total population ≈253.4 million). If one assumes a ratio of 1 neuroinvasive case for every 140 infections, which was the finding of a 1999 household-based seroepidemiologic survey in New York City ( 1 ), this yields an overall estimate of ≈411,880 infections and an estimated incidence of 0.16 infections per 100 people, or 0.0016 per person per year. Whether WNV epidemics will continue to occur in the United States at a similar frequency or intensity is unknown, but for this analysis we assumed that the risk for WNV infection would be 0.0016 per person per year for 10 years.…”

“…We assumed that symptoms of WNV illness will develop in 20% of infected persons and that neuroinvasive disease will develop in 3.6% of them, which is equivalent to 1 neuroinvasive case for every 140 infections previously described ( 1 ). We also assumed a vaccine effectiveness of 80% in reducing the risk for symptomatic illness.…”

“…West Nile virus (WNV) was first detected in the Western Hemisphere in 1999 during an outbreak of encephalitis in New York City ( 1 ). Over the next 6 years the virus spread across the continental United States, as well as into Canada, Latin America, and the Caribbean islands ( 2 , 3 ).…”

“…In 2002 alone, 2,942 cases of neuroinvasive WNV disease were reported in the United States, which represents the largest epidemic of neuroinvasive WNV disease ever recorded ( 4 ). Approximately 20% of WNV infections in humans result in symptomatic illness, and ≈1% of infections lead to encephalitis, meningitis, or acute flaccid paralysis ( 1 ). A substantial proportion of persons in whom severe neuroinvasive WNV disease develops have long-term disability or die as a result of their infection ( 5 , 6 ).…”