West Nile virus (WNV) is primarily transmitted to humans by infected mosquitoes.
More than 2,400 people have died of West Nile virus in the United States since it was first detected in New York City in 1999.
West Nile virus is usually spread through the bite of infected mosquitoes.
It is not spread person-to-person through casual contact.
In rare cases, WNV can be spread through blood transfusions, organ transplants, exposure in a lab setting or from mother to infant.
Symptoms of West Nile infection include: fatigue, fever, headache, body aches, rash and swollen lymph nodes.
80% of infected people do not display any symptoms.
According to the CDC, less than 1% of infected people develop a serious neuroinvasive illness, such as encephalitis (inflammation of the brain) or meningitis (inflammation of the protective membranes covering the brain and spinal cord).
There is no vaccine or specific treatment for WNV.
The most effective method of prevention is to avoid mosquito bites, by using insect repellent and by wearing protective clothing when outdoors.
1937 - The first case of West Nile virus is reported in Uganda. It is common throughout Africa, Central Asia and the Middle East.
August 1999 - The first cases of West Nile encephalitis in the Western Hemisphere are reported in the Bronx and Queens boroughs of New York. It is not known how the virus arrived in the United States.
2020 (preliminary) - As of May 25, 2021, 664 cases reported with 52 deaths.
2019 - 971 cases reported with 60 deaths.
2018 - 2,647 cases reported with 167 deaths.
2017 - 2,097 cases reported with 146 deaths.
2016 - 2,149 cases reported with 106 deaths.
2015 - 2,175 cases reported with 146 deaths.
2014 - 2,205 cases reported with 97 deaths.
2013 - 2,469 cases reported with 119 deaths.
2012 - 5,674 cases reported with 286 deaths.
2011 - 712 cases reported with 43 deaths.
2010 - 1,021 cases reported with 57 deaths.
2009 - 720 cases reported with 32 deaths.
2008 - 1,356 cases reported with 44 deaths.
2007 - 3,630 cases reported with 124 deaths.
2006 - 4,269 cases reported with 177 deaths.
2005 - 3,000 cases reported with 119 deaths.
2004 - 2,539 cases reported with 100 deaths.
2003 - 9,862 cases reported with 264 deaths.
2002 - 4,156 cases reported with 284 deaths.
2001 - 66 cases reported with 10 deaths.
2000 - 21 cases reported with two deaths.
1999 - 62 cases reported with seven deaths.