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West
Nile Virus: Q & A
Q. What can I do to reduce my risk of becoming infected with West Nile
virus? |
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 Here
are preventive measures that you and your family can take:
Protect yourself
from mosquito bites:
- Apply insect
repellent sparingly to exposed skin. The more DEET a repellent
contains the longer time it can protect you from mosquito bites. A
higher percentage of DEET in a repellent does not mean that your
protection is better—just that it will last longer. DEET
concentrations higher than 50% do not increase the length of
protection. Choose a repellent that provides protection for the
amount of time that you will be outdoors.
- Repellents
may irritate the eyes and mouth, so avoid applying repellent to
the hands of children.
- Whenever
you use an insecticide or insect repellent, be sure to read and
follow the manufacturer's DIRECTIONS FOR USE, as printed on the
product.
- For
detailed information about using repellents, see the Insect
Repellent Use below.
- Spray clothing
with repellents containing permethrin or DEET since mosquitoes may
bite through thin clothing. Do not apply repellents containing
permethrin directly to exposed skin. If you spray your clothing,
there is no need to spray repellent containing DEET on the skin
under your clothing.
- When possible,
wear long-sleeved shirts and long pants whenever you are outdoors.
- Place mosquito
netting over infant carriers when you are outdoors with infants.
- Consider
staying indoors at dawn, dusk, and in the early evening, which are
peak mosquito biting times.
- Install or
repair window and door screens so that mosquitoes cannot get
indoors.
Help reduce the
number of mosquitoes in areas outdoors where you work or play, by
draining sources of standing water. In this way, you reduce the number
of places mosquitoes can lay their eggs and breed.
- At least once
or twice a week, empty water from flower pots, pet food and water
dishes, birdbaths, swimming pool covers, buckets, barrels, and cans.
- Check for
clogged rain gutters and clean them out.
- Remove
discarded tires, and other items that could collect water.
- Be sure to
check for containers or trash in places that may be hard to see,
such as under bushes or under your home.
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Q. What can be done to
prevent outbreaks of West Nile virus?
A. Prevention and control of West Nile virus and other arboviral diseases is
most effectively accomplished through integrated vector management programs.
These programs should include surveillance for West Nile virus activity in
mosquito vectors, birds, horses, other animals, and humans, and implementation
of appropriate mosquito control measures to reduce mosquito populations when
necessary. Additionally, when virus activity is detected in an area, residents
should be alerted and advised to increase measures to reduce contact with
mosquitoes.
Q. Is there a vaccine
against West Nile encephalitis?
A. No, but several companies are working towards developing a vaccine.
Q. Where can I get
information about the use of pesticide sprays that are being used for mosquito
control?
A. The federal agency responsible for pesticide evaluation is the
Environmental Protection Agency (EPA). See
the EPA Web site
for detailed answers to the questions about pesticides used for mosquito
control.
Insect
Repellent Use
Q. Why should I use
insect repellent?
A. Insect repellents help people reduce their exposure to mosquito bites
that may carry potentially serious viruses such as West Nile virus, and allow
them to continue to play and work outdoors.
Q. When should I use
mosquito repellent?
A. Apply repellent when you are going to be outdoors and will be at risk
for getting bitten by mosquitoes.
Q. What time of day
should I wear mosquito repellent?
A. Many of the mosquitoes that carry the West Nile virus are especially
likely to bite around dusk and dawn. If you are outdoors around these times of
the day, it is important to apply repellent. In many parts of the country, there
are mosquitoes that also bite during the day, and these mosquitoes have also
been found to carry the West Nile virus. The safest decision is to apply
repellent whenever you are outdoors.
Q. How often should
repellent be reapplied?
A. Follow the directions on the product you are using in order to
determine how frequently you need to reapply repellent. Sweating, perspiration,
or getting wet may mean that you need to re-apply repellent more frequently. If
you are not being bitten, it is not necessary to re-apply repellent. Repellents
containing a higher concentration of active ingredient (such as DEET) provide
longer-lasting protection.
Q.
Should I wear repellent while I am indoors?
A. Probably not. If mosquitoes are biting you while you are indoors,
there are probably better ways to prevent these bites instead of wearing
repellent all the time. Check window and door screens for holes that may be
allowing mosquitoes inside. If your house or apartment does not have screens, a
quick solution may be to staple or tack screening (available from a hardware
store) across the windows. In some areas community programs can help older
citizens or others who need assistance.
Q. How does mosquito
repellent work?
A. Female mosquitoes bite people and animals because they need the
protein found in blood to help develop their eggs. Mosquitoes are attracted to
people by skin odors and carbon dioxide from breath. Many repellents contain a
chemical, N,N-diethyl-m-toluamide (DEET), which repels the mosquito, making the
person unattractive for feeding. DEET does not kill mosquitoes; it just makes
them unable to locate us. Repellents are effective only at short distances from
the treated surface, so you may still see mosquitoes flying nearby. As long as
you are not getting bitten, there is no reason to apply more DEET.
Q. Which mosquito
repellent works the best?
A. The most effective repellents contain DEET (N,N-diethyl-m-toluamide),
which is an ingredient used to repel pests like mosquitoes and ticks. DEET has
been tested against a variety of biting insects and has been shown to be very
effective. The more DEET a repellent contains the longer time it can protect you
from mosquito bites. A higher percentage of DEET in a repellent does not mean
that your protection is better—just that it will last longer. DEET
concentrations higher than 50% do not increase the length of protection.
Q.
How does the percentage of DEET in a product relate to the amount of protection
it gives?
A. Based on a recent study:
- A product containing
23.8% DEET provided an average of 5 hours of protection from mosquito bites.
- A product containing
20% DEET provided almost 4 hours of protection
- A product with 6.65%
DEET provided almost 2 hours of protection
- Products with 4.75%
DEET and 2% soybean oil were both able to provide roughly 1 and a half hour
of protection.
Choose a repellent that
provides protection for the amount of time that you will be outdoors. A higher
percentage of DEET should be used if you will be outdoors for several hours
while a lower percentage of DEET can be used if time outdoors will be limited.
You can also re-apply a product if you are outdoors for a longer time than
expected and start to be bitten by mosquitoes.
Q. Why is DEET
recommended?
A. DEET is the most effective and best-studied insect repellent
available. (Fradin, 1998). Studies using humans and mosquitoes report that only
products containing DEET offer long-lasting protection after a single
application.
Q. Are non-DEET
repellents effective (e.g. Skin-So-Soft, plant-based repellents)?
A. Some non-DEET repellent products which are intended to be applied
directly to skin also provide some protection from mosquito bites. However,
studies have suggested that other products do not offer the same level of
protection, or that protection does not last as long as products containing DEET.
A soybean-oil-based product has been shown to provide protection for a period of
time similar to a product with a low concentration of DEET (4.75%)
People should choose a
repellent that they will be likely to use consistently and that will provide
sufficient protection for the amount of time that they will be spending
outdoors. Product labels often indicate the length of time that protection that
can be expected from a product. Persons who are concerned about using DEET may
wish to consult their health care provider for advice. The National Pesticide
Information Center (NPIC) can also provide information through a toll-free
number, 1-800-858-7378 or http://npic.orst.edu/
.
Q. I'm confused. None
of the products in the store says "DEET".
A. Most insect repellents that are available in stores are labeled with
the chemical name for DEET. Look for N,N-diethyl-m-toluamide or, sometimes,
N,N-diethyl-3-methylbenzamide. Choose a repellent that offers appropriate
protection for the amount of time you will be outdoors. A higher percentage of
DEET should be used if you will be outdoors for several hours while a lower
percentage of DEET can be used if time outdoors will be limited.
Using Repellents Safely
Q. Is DEET safe?
A. Yes, products containing DEET are very safe when used according to the
directions. Because DEET is so widely used, a great deal of testing has been
done. When manufacturers seek registration with the U.S. Environmental
Protection Agency (EPA) for products such as DEET, laboratory testing regarding
both short-term and long-term health effects must be carried out. Over the long
history of DEET use, very few confirmed incidents of toxic reactions to DEET
have occurred when the product is used properly.
Q. What are some
general considerations to remember in order to use products containing DEET
safely?
A. Always follow the recommendations appearing on the product label.
- Use enough repellent
to cover exposed skin or clothing. Don't apply repellent to skin that is
under clothing. Heavy application is not necessary to achieve protection.
- Do not apply repellent
to cuts, wounds, or irritated skin.
- After returning
indoors, wash treated skin with soap and water.
- Do not spray aerosol
or pump products in enclosed areas.
- Do not apply aerosol
or pump products directly to your face. Spray your hands and then rub them
carefully over the face, avoiding eyes and mouth.
Q. How should products
containing DEET be used on children?
A. No definitive studies exist in the scientific literature about what
concentration of DEET is safe for children. The American Academy of Pediatrics
has recommended that a cautious approach is to use products with a low
concentration of DEET, 10% or less, on children aged 2 - 12. Most guidelines
cite that it is acceptable to use repellents containing DEET on children over 2
years of age. Other experts suggest that it is acceptable to apply repellent
with low concentrations of DEET to infants over 2 months old. It is recommended
that for children under 2 years of age only one application per day of repellent
containing DEET should be used.
Repellent products that
do not contain DEET are not likely to offer the same degree of protection from
mosquito bites as products containing DEET. Non-DEET repellents have not
necessarily been as thoroughly studied as DEET, and may not be safer for use on
children.
Parents should choose the
type and concentration of repellent to be used by taking into account the amount
of time that a child will be outdoors, exposure to mosquitoes, and the risk of
mosquito-transmitted disease in the area. Persons who are concerned about using
DEET or other products on children may wish to consult their health care
provider for advice. The National Pesticide Information Center (NPIC) can also
provide information through a toll-free number, 1-800-858-7378 or http://npic.orst.edu.
Always follow the
recommendations appearing on the product label when using repellent.
- When using repellent
on a child, apply it to your own hands and then rub them on your child.
Avoid children's eyes and mouth and use it sparingly around their ears.
- Do not apply repellent
to children's hands. (Children tend to put their hands in their mouths.)
- Do not allow young
children to apply insect repellent to themselves; have an adult do it for
them. Keep repellents out of reach of children.
- Do not apply repellent
to skin under clothing. If repellent is applied to clothing, wash treated
clothing before wearing again.
Using repellents on the
skin is not the only way to avoid mosquito bites. See the
Prevention
of West Nile Virus questions for details.
Q. Is DEET safe for
pregnant or nursing women?
A. There are no reported adverse events following use of repellents
containing DEET in pregnant or breastfeeding women.
Q. Are there any risks
due to using repellents containing DEET?
A. Use of these products may cause skin reactions in rare cases. If you
suspect a reaction to this product, discontinue use, wash the treated skin, and
call your local poison control center. There is a new national number to reach a
Poison Control Center near you: 1-800-222-1222.
If you go to a doctor,
take the product with you. Cases of serious reactions to products containing
DEET have been related to misuse of the product, such as swallowing, using over
broken skin, and using for multiple days without washing skin in between use,
for example. Always follow the instructions on the product label.
Q.
Can I put DEET on my pets to protect them from mosquito bites?
A. It is recommended that you do not apply repellents with DEET to
animals, because they may lick themselves and therefore "eat" the
product. You may want to check with your veterinarian for suggestions if a pet
is being bothered by mosquitoes.
See also the
West
Nile Virus and Animals page to learn more about pets and West Nile
virus.
Repellents and Schools
Q. Should parents
spray insect repellent on their children before they go to school?
A. Whether children spend time outside during the school day should
determine the need for applying repellent. Because most schools in the United
States have air conditioning, children's exposure to mosquitoes during the
school day is not likely to be high. If children will be spending time outdoors
(for example, in recreational activities, walking to and from school), parents
may wish to apply repellent. Mosquito repellent containing DEET is the most
effective in providing long-lasting protection from mosquito bites.
Q. Should children be
given repellent to use during the day?
A. The age and maturity of the child should be taken into account before
giving repellent to children for their own use. As with many other chemicals,
care should be taken that DEET is not misused or swallowed. Parents should find
out if a child will be outside during the school day, and should discuss proper
use of the product with their children. Parents should also consult local
officials to obtain policies and procedures specific to bringing repellent to
school.
More Information About
Repellents
Q. Where can I get
more information about repellents?
A. For more information about using repellents safely please consult the
EPA Web site: http://www.epa.gov/pesticides/citizens/insectrp.htm
or consult the National Pesticide Information Center (NPIC), which is
cooperatively sponsored by Oregon State University and the U.S. EPA. NPIC can be
reached at: http://npic.orst.edu/
or 1-800-858-7378.
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