Cases
of West Nile Human Disease
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.