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What is West Nile Virus (WNV)
Encephalitis?
West Nile virus (WNV)
encephalitis is a rare disease caused by a virus.
In a small percentage of people infected by the virus, the
disease can be serious, even fatal.
The virus that causes WNV encephalitis occurs in Europe, Africa
and Asia. It was first
identified in the United States during the summer of 1999.
It is not known how WNV got to the U.S.
WNV grows in birds, and it is transmitted from bird to bird and
from birds to humans by mosquitoes.
Horses bitten by mosquitoes carrying WNV can also become sick.
What are the symptoms of
WNV Encephalitis?
Mild WNV infections cause
fever, headache and body aches, often with a skin rash and swollen lymph
glands. More severe
infections can cause headache, high fever, neck stiffness, stupor,
disorientation, coma, tremors, convulsions, paralysis and, sometimes,
death.
Is there treatment for WNV
Encephalitis?
There is no treatment for WNV
infection. Doctors can
treat the symptoms of WNV encephalitis.
However, about 7% of people who become sick enough from the
infection to be hospitalized die from it.
How is WNV spread?
WNV is spread only by adult
mosquitoes that are infected with the virus.
People and horses that have WNV infection cannot spread the
disease without mosquitoes. The risk of getting WNV encephalitis is
highest from late July through September.
There is no evidence that a person can get WNV from handling live
or dead infected birds. Still,
you should avoid barehanded contact when handling dead animals,
including birds. If you
must handle dead birds, use gloves or double plastic bags.
If you notice unusual numbers of dead birds in your area, call
your local board of health or the Massachusetts Department of Public
Health.
What can you do to
protect yourself?
There is no vaccine for WNV.
The only way to protect yourself is to keep mosquitoes from
biting you. Follow these
steps every summer if you live in or visit an area with mosquitoes:
- Avoid outdoor activities between dusk and dawn, if possible, as
this is the time of greatest mosquito activity.
- If you must be outdoors when mosquitoes are active, wear a
long-sleeved shirt and long pants. Use a mosquito repellent that
contains DEET (the chemical N-N-diethyl-meta-toluamide) and follow
the directions on the label. DEET can be poisonous if
overused. Never use DEET on infants. Avoid using repellents
with DEET concentrations above 10-15% for children and with
concentrations above 30-35% for adults. Cream, lotion or stick
formulas are best. Avoid products with high amounts of alcohol.
- Take special care to cover up the arms and legs of children
playing outdoors. When you bring a baby outdoors, cover the baby’s
carriage or playpen with mosquito netting.
- Fix any holes in your screens and make sure they are tightly
attached to all your doors and windows.
What can you do to reduce the number of mosquitoes around your home
and neighborhood?
To reduce mosquito populations
around your home and neighborhood, get rid of any standing water that is
available for mosquito breeding. Mosquitoes will breed in any puddle or
standing water that lasts for more than four days.
Here are some simple steps you can take:
- Dispose of or regularly empty any metal cans, plastic containers,
ceramic pots and other water holding containers (including
trashcans) on your property.
- Pay special attention to discarded tires that may have collected
on your property. Tires are a common place for mosquitoes to breed.
- Drill holes in the bottom of recycling containers that are left
outdoors, so that water can drain out.
- Clean clogged roof gutters; remove leaves and debris that may
prevent drainage of rainwater.
- Turn over plastic wading pools and wheelbarrows when not in use.
- Do not allow water to stagnate in birdbaths; aerate ornamental
ponds or stock them with fish.
- Keep swimming pools clean and properly chlorinated; remove
standing water from pool covers.
- Use landscaping to eliminate standing water that collects on your
property.
What is Massachusetts
doing to protect people from WNV?
The Massachusetts Department of
Public Health (MDPH) has had a long-standing program to look for another
virus carried by mosquitoes, Eastern Equine Encephalitis virus.
Every year from May until the first frost, MDPH field staff
collects mosquitoes and bring them to the State Laboratory for testing.
MDPH has expanded this mosquito surveillance program to look for
WNV throughout Massachusetts. Under
this expanded program, mosquito collections will be increased and more
sites will be sampled. Also,
a system is in place to test dead birds to look for the presence of WNV.
The State Laboratory can also test for WNV infection in horses
and humans. If WNV is
detected in Massachusetts, MDPH will alert local boards of health,
hospitals, and people who live in the area.
Steps You Can Take To Prevent West Nile Virus
Massachusetts Department of Public Health
Division of Epidemiology and Immunization
April 2000
How
can I protect myself and my family from mosquito bites?
There is no vaccine for West Nile virus (WNV). The only way to
protect yourself is to keep mosquitoes from biting you. Follow these
steps every summer if you live in or visit an area with mosquitoes:
- Avoid outdoor activities between dusk and dawn, if possible, since
this is the time when mosquitoes are most active.
- If you must be outdoors when mosquitoes are active, wear a
long-sleeved shirt and long pants.
- Use a mosquito repellent that contains DEET (the chemical
N-N-diethyl-meta-toluamide) and follow the directions on the label.
DEET can be toxic if overused. Never use DEET on infants. Avoid
using repellents with DEET concentrations above 10-15% for children
and with concentrations above 30-35% for adults. Cream, lotion or
stick formulas are best. Avoid products with high amounts of
alcohol.
- Most mosquito repellents will remain effective for many hours, so
it is not necessary to reapply the repellent. Once inside, wash off
insect repellents thoroughly with soap and water.
- Take special care to cover up the arms and legs of children
playing outdoors. When you bring a baby outdoors, cover the baby’s
carriage or playpen with mosquito netting.
- Fix any holes in your screens and make sure they are tightly
attached to all your doors and windows
How can I reduce the number of mosquitoes around my
home and neighborhood?
To reduce mosquito populations around your home and neighborhood, get
rid of any standing water that is available for mosquito breeding.
Mosquitoes will breed in any puddle or standing water that lasts for
more than four days. Here are some simple steps you can take:
- Dispose of or regularly empty any metal cans, plastic containers,
ceramic pots, and other water-holding containers (including
trashcans) on your property.
- Pay special attention to discarded tires that may have collected
on your property. Tires are a common place for mosquitoes to breed.
- Drill holes in the bottom of recycling containers that are left
outdoors, to let water drain out.
- Clean clogged roof gutters; remove leaves and debris that may
prevent drainage of rainwater.
- Turn over plastic wading pools and wheelbarrows when not in use.
- Do not allow water to stagnate in birdbaths; aerate ornamental
ponds or stock them with fish.
- Keep swimming pools clean and properly chlorinated; remove
standing water from pool covers.
- Use landscaping to eliminate standing water that collects on your
property.
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