Transcript West Nile Virus

Fight the Bite!
The West Nile Virus
Updated and current as of 17 July 2003
Infection Area so far in 2003 as of July 16, 2003
Human cases in the U.S. in 2003
Human Cases in the U.S. in 2002
Human cases in Ohio in 2002
Montgomery
County
Background
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Since West Nile virus (WNV) was first isolated in 1937, it has been known to
cause asymptomatic infection and fevers in humans in Africa, West Asia, and
the Middle East.
Human and animal infections were not documented in the Western
Hemisphere until 1999.
In 1999 and 2000, outbreaks of WNV encephalitis (inflammation of the brain)
were reported in persons living in the New York City metropolitan area, New
Jersey, and Connecticut. In these two years, 83 human cases of West Nile
illness were reported; 9 died.
In 2001, human infection with WNV occurred in 10 states with 66 cases and
9 deaths.
In 2002, WNV activity spread to 44 states, with 4,156 human cases and 284
deaths.
Transmission
• WNV is transmitted to humans through
mosquito bites. Mosquitoes become
infected when they feed on infected birds
that have high levels of WNV in their
blood. Infected mosquitoes can then
transmit WNV when they feed on
humans or other animals.
• WNV is not transmitted from person to
person and there is no evidence that a
person can get infected by handling live
or dead infected birds. But, to add a
further level of safety, if birds or other
potentially infected animals must be
handled, a protective barrier (e.g.,
gloves, inverted plastic bags) should be
used.
Symptoms
• Most WNV infected humans have no
symptoms.
• A small proportion develops mild symptoms that
include fever, headache, body aches, skin rash
and swollen lymph glands.
• Less than 1% of infected people develop more
severe illness that includes meningitis
(inflammation of the spinal cord) or encephalitis.
• The symptoms of these illnesses can include
headache, high fever, neck stiffness, stupor,
disorientation, coma, tremors, convulsions,
muscle weakness, and paralysis.
• Of the few people that develop encephalitis, a
small proportion die but, overall, this is
estimated to occur in less than 1 out of 1000
infections.
Treatment
• There is no specific treatment for WNV infection or
vaccine to prevent it.
• Treatment of severe illnesses includes hospitalization, use
of intravenous fluids and nutrition, respiratory support,
prevention of secondary infections, and good nursing
care.
• Medical care should be sought as soon as possible for
persons who have symptoms suggesting severe illness.
Reducing Exposure
• Individuals can reduce their contacts with
mosquitoes by taking these actions:
• When outdoors, wear clothing that covers the
skin such as long sleeve shirts and pants,
• Apply effective insect repellent to clothing and
exposed skin, and
• Curb outside activity during the hours that
mosquitoes are feeding which often includes
dawn and dusk.
• In addition, screens should be applied to doors
and windows and regularly maintained to keep
mosquitoes from entering the home.
Q and A from the CDC
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Symptoms of West Nile Virus
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Q. What are the symptoms of West Nile virus infection?
A. Most people who are infected with the West Nile virus will not have any type of
illness. It is estimated that 20% of the people who become infected will develop West
Nile fever: mild symptoms, including fever, headache, and body aches, occasionally
with a skin rash on the trunk of the body and swollen lymph glands.
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The symptoms of severe infection (West Nile encephalitis or meningitis) include
headache, high fever, neck stiffness, stupor, disorientation, coma, tremors,
convulsions, muscle weakness, and paralysis. It is estimated that 1 in 150 persons
infected with the West Nile virus will develop a more severe form of disease.
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Q. What is the incubation period in humans (i.e., time from infection to onset of
disease symptoms) for West Nile encephalitis?
A. Usually 3 to 14 days.
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Q. How long do symptoms last?
A. Symptoms of mild disease will generally last a few days. Symptoms of severe
disease may last several weeks, although neurological effects may be permanent.
Avoiding Exposure - fight the bite
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When dealing with West Nile virus, prevention is your best bet. Fighting
mosquito bites reduces your risk of getting this disease, along with
others that mosquitoes can carry. Take the commonsense steps below
to reduce your risk, and you'll:
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Avoid bites and illness;
Clean out the mosquitoes from the places where you work and play;
Help your community control the disease.
Reduce your risk 3 ways
Step 1 - Avoiding bites
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Avoid Mosquito Bites
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Apply Insect Repellent Containing DEET
(Look for: N,N-diethyl-meta-toluamide) to exposed skin when you go
outdoors. Even a short time being outdoors can be long enough to get a
mosquito bite. Always follow the manufacturer indications for use, and note
that repellants are recommended for small children.
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Clothing Can Help Reduce Mosquito Bites
When possible, wear long-sleeves, long pants and socks when outdoors.
Mosquitoes may bite through thin clothing, so spraying clothes with
repellent containing permethrin or DEET will give extra protection. Don't
apply repellents containing permethrin directly to skin. Do not spray
repellent containing DEET on the skin under your clothing.
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Be Aware of Peak Mosquito Hours
The hours from dusk to dawn are peak mosquito biting times for many
species of mosquitoes. Take extra care to use repellent and protective
clothing during evening and early morning -- or consider avoiding outdoor
activities during these times.
Step 2 - Mosquito-Proof Your Home
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Mosquito-Proof Your Home
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Drain Standing Water
Mosquitoes lay their eggs in standing
water.Limit the number of places around your
home for mosquitoes to breed by getting rid
of items that hold water.
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Install or Repair Screens
Some mosquitoes like to come indoors. Keep
them outside by having well-fitting screens on
both windows and doors. Offer to help
neighbors whose screens might be in bad
shape.
Step 3 - Help Your Community
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Help Your Community
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Report Dead Birds to Local Authorities
Dead birds may be a sign that West Nile virus is circulating between birds and the
mosquitoes in an area. Over 130 species of birds are known to have been infected with
West Nile virus, though not all infected birds will die. It's important to remember that
birds die from many other causes besides West Nile virus.
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By reporting dead birds to state and local health departments, you can play an important
role in monitoring West Nile virus. Keep in mind that state and local agencies have
different policies for collecting and testing birds. Also be sure to handle dead birds with
gloves.
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Clean Up
Mosquito breeding sites can be everywhere. Neighborhood clean up days can be
organized by civic or youth organizations to pick up containers from vacant lots and
parks, and to encourage people to keep their yards free of standing water. Mosquitoes
don't care about fences, so it's important to control breeding sites anywhere in the
neighborhood.
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Find out more about local prevention efforts
Find out what state and local officials are doing to help control West Nile virus.
Mosquito Control with Pesticides
1. 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.
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Microbial larvicides such as Bacillus thuringiensis var. israelensis and Bacillus sphaericus can
be used successfully in a broad range of freshwater habitats.
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Biochemical larvicides (insect growth regulators - IGRs) such as methoprene can also be used
in a variety of habitats.
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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.
2. 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.
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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.
References
• The U.S. Centers for Disease Control and Prevention
(CDC),
– see website http://www.cdc.gov/westnile/index.htm.
• The U.S. Geological Survey (USGS)
– See website http://westnilemaps.usgs.gov/.
• The Ohio Department of Health
– See website
http://www.odh.state.oh.us/ODHPrograms/ZOODIS/WNV/wnv1.htm.