August 27, 2004
·
A
second human case of West Nile virus infection this year has been identified in
Manitoba. The individual, a resident of
the Assiniboine Regional Health Authority in his forties, has not been
hospitalized. The individual has been
reported to Health Canada as a probable case of West Nile fever.
·
The
likeliest period of exposure to West Nile virus for this individual was during
the last week of July or the first week of August.
·
Usually,
people infected by West Nile virus have no symptoms and do not become
ill. Of those who do become ill, most will develop West Nile fever, an
illness with symptoms such as fever, headache, fatigue and body aches.
Less frequently, the virus can cause more serious illness (West Nile
neurological syndrome) including encephalitis, an inflammation of the brain.
·
Encephalitis
can have serious complications. These complications may include weakness,
paralysis, confusion, coma and death and are more likely to occur among older
adults and people with chronic diseases and weakened immune systems.
·
There
is no vaccine or specific treatment for West Nile virus. Milder symptoms
of West Nile fever usually improve without medical care. Anyone
experiencing severe symptoms (such as persistent high fever, muscle weakness,
headache) should seek medical attention promptly for diagnosis and care.
·
Although
mosquito counts have been low, some infected mosquitoes in southern Manitoba
may become more active, particularly during warmer evenings or during humid,
overcast days. Personal protection should be considered at any time when
mosquito activity is noticed, especially for people over the age of 50 or with
chronic medical conditions or weakened immune systems.
·
Based
on mosquito surveillance, the time of year and the life cycle of the Culex
tarsalis mosquito, the current risk of becoming infected with West Nile
virus in Manitoba is considered low and is expected to decrease.
·
While
it is anticipated that additional human cases of WNV will be identified in
Manitoba this season, it is expected that exposure to the virus in most newly
identified cases will likely have occurred in late July or early August.
·
The
most current mosquito surveillance information for southern Manitoba indicates
that the activity of Culex tarsalis, the main mosquito species that
carries West Nile virus in Manitoba, remained low in all regional health
authorities during the week of Aug. 15 to 21.
·
The
average trap counts for Culex tarsalis in regional health authorities
gathered during the week of Aug. 15 to 21 were: Assiniboine, 11; Brandon,
one; Central, three; Interlake, two; North Eastman, zero; Parkland, one; South
Eastman, 10; and Winnipeg, 32.
·
In
2004, infected mosquitoes have been found in the following communities:
Brandon, Souris, Deloraine, Killarney, Winkler, Winnipeg, West St. Paul
and East St. Paul. The infection rate of trapped mosquitoes remains low,
less than one per 1,000 mosquitoes.
·
At
this time of year and during the rest of this season it is expected that newly
hatched Culex tarsalis mosquitoes will not blood-feed (i.e. bite), and
therefore pose little risk of West Nile virus transmission.
·
Public
information about West Nile virus is available by calling Health Links-Info
Santé at 788-8200 in Winnipeg or toll-free at 1-888-315-9257. Additional
information is available on the Manitoba Health website at http://www.gov.mb.ca/health/wnv,
which is updated with surveillance data weekly.
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