What
You Need To Know About West Nile virus
West
Nile virus (WNV) is a new disease in Manitoba. The virus is
transmitted by mosquitoes. Most people who are bitten by an
infected mosquito do not become ill and for those who do,
the symptoms are usually mild. In some cases, the virus causes
serious illness and sometimes death.
Human cases of West Nile virus were first detected
in (southern) Manitoba in summer 2003, when 143 cases were
identified. Of these 143 cases, 35 people suffered a serious
illness, including two deaths.
In 2004, there were three human cases and no
deaths; in 2005, 58 cases were identified, including one death.
Most mosquitoes do not carry WNV. In Manitoba,the
main carrier of the virus is the Culex mosquito,
which is usually less common than other mosquito types.
The risk of WNV varies from year to year. The
risk is influenced by precipitation, temperature, mosquito
populations and many other factors. Manitobans are at highest
risk of being bitten by a WNV-infected mosquito in July, August
and early September. Mosquito traps are monitored throughout
the summer to help provide regular, ongoing information on
the risk of West Nile virus.
How new is WNV?
West Nile virus was first identified in Africa
in 1937 and after that, in Europe. It was reported in North
America in New York City in 1999. Since then it has been identified
in most of the U.S. and many parts of Canada. In Manitoba,
WNV was first detected in birds of the crow family, horses
and mosquitoes in July 2002.
What are
the symptoms?
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. People with pre-existing medical
conditions and older adults are more at risk for severe illness.
However, illness has occurred in all age groups. Encephalitis
can have serious complications. These complications may include
weakness, paralysis, confusion, coma or death.
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 (ex: persistent
high fever, muscle weakness, headache) should seek medical
attention promptly for diagnosis and care.
For specific advice regarding medical care, contact your
health care provider. Or, you can call Health Links-Info Santé
at 788-8200 (in Winnipeg) or toll-free 1-888-315-9257.
How is it
spread?
People can become infected if they are bitten by mosquitoes
that have previously bitten infected birds. Even when WNV
has been identified in an area, most mosquitoes do not
carry the virus.
There are other less common ways that WNV maybe spread. Cases
from blood transfusions and tissue transplants have been observed,
but are rare. All donated blood is tested for the presence
of WNV.
There is also evidence to suggest that pregnant women can
pass the virus to their unborn babies, and that it may also
be passed on through breast milk. There is some evidence that
poultry workers exposed to a WNV outbreak among turkeys may
have become infected with WNV.
What can I do about
West Nile virus?![You can help reduce mosquito numbers by getting rid of mosquito habitats around your home.](/web/20061121072219im_/http://www.gov.mb.ca/health/wnv/images/birdbath.jpg)
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You can protect yourself by minimizing your
exposure to mosquito bites.
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You can help reduce mosquito numbers by
getting rid of mosquito habitats around your home.
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You can help detect West Nile virus in your
area by assisting with bird surveillance efforts
How can I protect myself?
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Reduce the time you
spend outdoors between dusk and dawn. The peak mosquito
hours are around dusk and dawn, but Culex mosquitoes
will also bite during the night.
![Check that door and window screens fit tightly and are free of holes.](/web/20061121072219im_/http://www.gov.mb.ca/health/wnv/images/window.jpg)
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Wear light-coloured,
loose-fitting, long-sleeved
tops and long pants when
outside, especially between dusk and dawn.
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Apply insect repellent
containing DEET, according to Health Canada Guidelines.
(DEET is not recommended
for children under the age of 6 months). For more
information, see the fact sheet Safety
Tips on Using Personal Insect Repellents.
- Check that door and window screens fit tightly and are
free of holes.
How can I reduce mosquito
habitats?
The
fewer Culex mosquitoes that hatch, the lower the
risk of WNV. Culex mosquitoes lay their eggs on standing water.
Even small amounts of water allowed to stand for a week or
more may produce adult mosquitoes.
To reduce the places around your home where
Culex mosquitoes may lay their eggs, eliminate unnecessary
standing water:
- Regularly clean and empty your eavestroughs, pool covers
and other items that might collect water.
- Clean and empty bird baths weekly.
- Ensure that openings in rain barrels are covered with
mosquito screening or tightly sealed around the downspout.
- Make sure your yard is clear of old tires or other debris
that collect water.
Adult mosquitoes like to rest in long grass and sheltered
shady areas. You may reduce your exposure to mosquitoes by
regularly maintaining these areas around your home. Steps
you can take include:
- cutting the grass around your home ; and
- trimming hedges and trees around doorways and outdoor
seating areas (ex: decks, patios, etc.)
For more information, see the fact sheet Reducing
Mosquito Numbers Around Your Home.
What is bird surveillance?
Birds from the crow family (corvids) are not
the main source of WNV in Manitoba. However, these birds are
very susceptible to the virus. Many die soon after becoming
infected. Testing dead crows and other corvids provides an
early indication of the presence of infected mosquitoes in
an area.
In Manitoba, dead corvids are no longer required
as an early indicator of WNV because information collected
over the past four years has confirmed when and where the
virus will appear. Manitoba Health will
continue to use other indicators, such as mosquito surveillance,
to determine the human health risk of WNV in the province.
If you need to dispose
of a dead bird, take the follow precautions:
- Don’t touch the
dead bird with your bare hands.
- Take care not to scratch
or puncture your skin while handling the bird. Use a shovel
or a plastic bag to pick it up.
- Dispose of the dead
bird with your usual household trash.
- Promptly wash your
hands well with soap and water.
For more information on
how to dispose a dead bird, see the fact sheet Disposing
of Dead Birds and Small Animals.
For photos and descriptions of corvids and maps,
see the website for the
Canadian Cooperative Wildlife Health Centre (CCHWC).
What about
outdoor recreation and work?
People
who spend a lot of time outdoors for recreation (ex: camping,
golfing) or work (ex: farming, construction) can follow the
same basic preventive measures as anyone else (see How
Can I Protect Myself?). These precautions are especially
important in back country areas where there are large amounts
of shallow, standing water.
Which pets and
livestock are at risk?
Horses bitten by infected mosquitoes can become
seriously ill and die. Younger domestic birds have also been
affected by WNV.
Disease due to WNV has not been reported among
cattle. Research has shown that weaning pigs may be susceptible
to the virus. Cases of infected dogs and cats have been reported
rarely.
For more detailed information on the West Nile
virus and livestock operations, contact the Veterinary Services
Branch of Manitoba Agriculture and Food in Winnipeg at (204)
945-7652.
What else do
I need to know?
West Nile virus is an emerging disease. New information about
the virus, and how to protect and control against it, continues
to evolve.
Ongoing efforts to detect the presence of the virus in mosquitoes
and people, combined with information and research from other
jurisdictions, will help guide public health recommendations
for mosquito control and other actions. For information about
specific mosquito control activities in your area, contact
your local municipality. For general information about mosquito
control, call HealthLinks-Info Santé (see below).
Summer in Manitoba is an opportunity to enjoy all kinds of
healthy outdoor activities. To protect yourself and your family
from exposure to mosquito bites, you can follow the basic
preventive measures outlined in this brochure when planning
outdoor activities.
For brochures and factsheets
related to West Nile virus, visit our Fact Sheets section.
For up-to-date information
about WNV in Manitoba:![mosquito](/web/20061121072219im_/http://www.gov.mb.ca/health/wnv/images/mosquito2.gif)
Health Links-Info Santé
Winnipeg: 788-8200
Elsewhere in Manitoba: toll-free 1-888-315-9257.
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