Nile virus (WNV) has emerged in recent years in temperate regions
of Europe and North America, presenting a threat to public and
animal health. The most serious manifestation of WNV infection
is fatal encephalitis (inflammation of the brain) in humans and
horses, as well as mortality in certain domestic and wild birds.
WNV has also been a significant cause of human illness in the
United States in 2002 and 2003.
Nile virus was first isolated from a febrile adult woman in the
West Nile District of Uganda in 1937. The ecology was characterized
in Egypt in the 1950s. The virus became recognized as a cause
of severe human meningitis or encephalitis (inflammation of the
spinal cord and brain) in elderly patients during an
outbreak in Israel in 1957. Equine disease was first noted in
Egypt and France in the early 1960s. WNV first appeared in North
America in 1999, with encephalitis reported in humans and horses.The
subsequent spread in the United States is an important milestone
in the evolving history of this virus.
Nile virus has been described in Africa, Europe, the Middle East,
west and central Asia, Oceania (subtype Kunjin), and most recently,
of WNV encephalitis in humans have occurred in Algeria in 1994,
Romania in 1996-1997, the Czech Republic in 1997, the Democratic
Republic of the Congo in 1998, Russia in 1999, the United States
in 1999-2003, and Israel in 2000. Epizootics of disease
in horses occurred in Morocco in 1996, Italy in 1998, the United
States in 1999-2001, and France in 2000, and in birds in Israel
in 1997-2001 and in the United States in 1999-2002.
the U.S. since 1999, WNV human, bird, veterinary or mosquito activity
have been reported from all states except Hawaii, Alaska, and
Human Case and Virus Distribution Information
case information and maps
1999 through 2001, there were 149 cases of West Nile virus human
illness in the United States reported to CDC and confirmed,
including 18 deaths.