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West Nile Virus Information
History
West Nile Virus is a mosquito-borne virus that can cause encephalitis
(inflammation of the brain) or meningitis (inflammation of the lining of the
brain and spinal cord). Outbreaks of the West Nile Virus have occurred before in
Egypt, Asia, Israel, South Africa, and in some parts of Europe. West Nile Virus
was first found in the United States in New York City in the fall of 1999. In
2001, Ohio had birds and mosquitos that tested
positive for West Nile Virus. In 2002, Ohio had its first human case of West
Nile Virus and eventually had a total of 441 human cases of West Nile Virus.
There were 39 states that had human cases of West Nile Virus in 2002. While we
are uncertain how West Nile Virus first arrived in the USA, the most likely
explanation is that the virus was introduced by an infected bird that was
imported or an infected human returning from a country where the virus is
common, or a mosquito hitchhiking on an airplane.
Transmission Cycle
West Nile Virus
is spread to humans by the bite of an infected mosquito. When a mosquito bites a
bird that carries the virus, the mosquito becomes infected. It is believed that
people cannot get West Nile Virus directly from another person, or animal, that
has the disease. It is believed that this disease is only transmitted by
mosquitoes.
Being bitten by an
infected mosquito will not necessarily make you sick, since most people who are
infected with West Nile Virus either have no symptoms or experience mild
illness. If illness were to occur, it would occur within 5 to 15 days of being
bitten by an infected mosquito.
In 2003, the first
positive birds were found in Ohio on June 12. There have been 1,493 birds tested
and 119 were positive. As of August 29, there were 276,149 mosquitoes tested for
West Nile Virus with 235 positive pools of mosquitoes. There were 151 horses
tested and 5 have tested positive. The first human case was confirmed on July 18
in Fulton County. There have been 12 human cases in Ohio so far, four of which
are West Nile Fever and the remainder are West Nile Encephalitis/Meningitis. One
person has died.
In 2002, the first two
human cases of West Nile Virus (WNV) in Ohio were reported on August 14, 2002,
one from Cuyahoga County and one from Franklin County. That year, there were 299
probable and 142 confirmed cases of WNV in Ohio. Confirmatory tests are
conducted by the Centers for Disease Control and Prevention in Fort Collins,
Colorado. There were 31 deaths.
In
2002, ODH's Vector borne Disease Program tested
5,152 dead and live birds. Among these, there were 1,002 birds with WNV. These
positive birds include: blue jays, American crows and other birds. There
were over 185,372 mosquitoes tested for West Nile Virus and 1,976 positive pools
of mosquitoes were found. Of 1,308 horses tested by the Ohio Department of
Agriculture's Animal Disease Diagnostic Laboratory for WNV, 645 were positive
and about one third have died or were euthanized.
West Nile Virus was found in all 88 of Ohio's counties in 2002.
In
2001, ODH's Vector borne Disease Program tested
1,848 live birds. Among these, there were six birds with WNV from three
counties. There were 942 dead birds submitted for testing to the Ohio Department
of Agriculture. Of these, 54 blue jays and 226 crows have tested positive. There
were 91,590 mosquitoes tested for WNV and 26 positive pools of Culex
sp. mosquitoes were found. Of 969 horses tested, all were negative.
There were 274 humans tested at the Ohio Department of Health laboratory for
West Nile Virus in Ohio and all were negative.
Maps of West Nile Virus
What you can do to prevent West Nile Virus
Mosquitoes lay their eggs in standing
water, which includes puddles, stagnant ditches, and containers such as old
tires, buckets, cans, neglected swimming pools, etc. Storm sewers, culverts, and
catch-basins, etc. provide an outdoor resting place for adult Culex pipiens
mosquito (the common house mosquito) which is most commonly associated with West
Nile virus. This mosquito often enters homes through unscreened windows or
doors, or broken screens.
 | Make sure that doors and windows have tight-fitting screens. Repair or
replace all torn screens in your home.
| Remove all discarded tires from your property.
| Dispose of tin cans, plastic containers, ceramic pots, or similar
water-holding containers.
| Make sure roof gutters drain properly. Clean clogged gutters in the spring
and fall.
| Clean and chlorinate swimming pools, outdoor saunas and hot tubs. If not
in use, keep empty and covered.
| Drain water from pool covers.
| Change the water in bird baths at least once a week.
| Turn over plastic wading pools, and wheelbarrows, etc. when not in use.
| Clean ditches of obstructions so they drain properly.
| Eliminate any standing water that collects on your property.
| Check trees for cavities that hold water and fill them with soil, gravel,
or sand.
| Remind or help neighbors to eliminate breeding sites on their properties. |
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Repellents
If you will be outside during evening, nighttime and dawn hours, consider
the use of an insect repellant containing 10% or less DEET (N,
N-diethyl-methyl-meta-toluamide) for children and no more than 30% DEET for
adults. DEET is effective for approximately four hours. Avoid prolonged or
excessive use of DEET and use it sparingly to cover exposed skin and clothing.
Do not use DEET on infants or pregnant women and do not apply DEET directly to
children. Apply it to your own hands and then put it on the child. Always use
DEET according to the manufacturer’s instructions.
Remember that Vitamin B, ultrasonic devices, incense and bug zappers have not
been shown to be effective in preventing mosquito bites.
Mosquito Control with Pesticides
- Larvicides can be used to control mosquitoes in the aquatic stage before
they become biting adults. This type of control generally has the least
effect on non-target species and the environment.
| Microbial larvicides such as Bacillus thuringiensis var. israelensis
and Bacillus sphaericus can be used successfully in a broad range of
freshwater habitats. |
| Biochemical larvicides (insect growth regulators - IGRs) such as
methoprene can also be used in a variety of habitats. |
| Mono-molecular surface film larvicides can be used in polluted or
artificial habitats, but should not be used where non-target insects are
important resources. |
- Mosquito adulticides should be considered the least desirable method of
control and only used when isolations of virus and/or evidence of disease
has been established. These materials have strengths and drawbacks that will
influence which material is most appropriate for a given situation, and all
must be applied according to label directions. Currently available
adulticides include organophosphates, pyrethrins, and pyrethroid-based
insecticides. These may be applied by hand-held, or backpack, foggers, or
fixed-wing or rotary-wing aircraft.
Application of adulticides by truck-mounted foggers, fixed-wing or
rotary-wing aircraft is usually done by government agencies or private
contractors. Those who apply pesticides in these ways must be licensed, have
their equipment properly calibrated, and adhere to the label directions.
The staff of the Fayette County Health District is monitoring West Nile Virus
activity in Fayette and surrounding counties.
Follow the link below for
information on this virus:
Centers For
Disease Control: West Nile Virus
The staff of the Fayette County Health District is monitoring West Nile Virus
activity in Fayette and surrounding counties. For more information call the Fayette County Health District, Division of
Environmental Health 740 333-3590 |
