Q. How many cases of West Nile disease in humans have occurred in the U.S.?
A. Our Statistics, Surveillance, and Control page contains maps showing the distribution of West Nile virus-related human disease cases, by state, in the U.S. in 2004.

Please see CDC's current case count for the number and nature of human cases of West Nile virus-related disease reported in the U.S. in 2004.

In 2003, there were 9862 human cases of WNV disease reported, including 264 deaths. For a report of cases by clinical syndrome and by state, please see the 2003 human disease cases.

In 2002, there were 4156 human cases of WNV disease, including 284 deaths. Cases were reported throughout much of the US; for a report of cases by each state please refer to the 2002 human case count. In 2001, there were 66 human cases of severe disease and 9 deaths. In 2000, 21 cases were reported, including 2 deaths in the New York City area. In 1999, 62 cases of severe disease, including 7 deaths, occurred in the New York area.  

There are no reliable estimates are available for the number of cases of West Nile encephalitis that occur worldwide.

Q. What proportion of people with severe illness due to West Nile virus die?
A. Among those with severe illness due to West Nile virus, case-fatality rates range from 3% to 15% and are highest among the elderly.

Less than 1% of people who become infected with West Nile virus will develop severe illness -- most people who get infected do not develop any disease at all.