| West Nile
Virus |
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| General Information |
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West Nile Virus (WNV)
is a member of the family Flaviviridae and is closely related to
several mosquito-transmitted flaviviruses that cause human disease
on different continents, including St. Louis encephalitis (SLE)
virus, a native North American arbovirus. Both WNV and SLE viruses
are maintained in a transmission cycle involving birds and
mosquitos.
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WNV was first isolated
in 1937 in the West Nile district of Uganda, Africa. Outbreaks of
WNV have occurred in a number of countries including Egypt, Israel,
South Africa, and countries in parts of Asia and Europe. Recent
outbreaks, outside of North America, have occurred in France and
Israel in 2000, Russia in 1999, and Romania in 1996-97.
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WNV was first detected
in the United States in September 1999 during the investigation of
an outbreak of encephalitis in humans in New York City.
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WNV is spread to
humans by the bite of an infected mosquito. A mosquito becomes
infected by feeding on the blood of a bird that carries the virus.
Approximately two weeks must elapse after a mosquito has fed on an
infected bird before it is capable of transmitting the virus to a
human or animal. There is no evidence to suggest that an individual
could get WNV from another person. For example, WNV cannot be spread
through touching or kissing an infected person, or from exposure to
a health care worker who has treated someone infected with WNV.
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| Surveillance |
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The number of bird
species in North America that play a role in the transmission of WNV
is not known at this time, although the virus has been identified in
more than 100 species of birds in the USA between 1999-2001. High
mortality rates occur in some bird species, particularly the
Corvidae (American crows [Corvus
brachyrhynchos], blue jays [Cyanocitta
cristata], gray jays [Perisoreus
canadensis], magpies [Pica
hudsonia], and ravens [Corvus
corax]). The
Canadian Cooperative Wildlife Health Centre is currently involved in collecting dead birds for
surveillance of West Nile Virus in Canada. See visit their
website for further details.
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For general information on WNV, visit
Health Canada's website.
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For recent updates on WNV surveillance by province and
general information provided by Health Canada, click
here.
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In British Columbia between
2007 and 2014, WNV has been reported in:
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25 people, of which 21
cases are suspected of being contracted outside of the province;
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5 horses, 6 birds (corvids)
as well as in mosquitos.
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For information on WNV in
jurisdictions surrounding BC, see the following:
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| Further Reading |
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