Elk Grove Community
West Nile Virus Information
West Nile Virus
Frequently Asked Questions
Overview of West Nile Virus
Q: What are West Nile virus, West Nile fever, and West Nile encephalitis?
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A."West Nile Virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St. Louis encephalitis virus found in the United States. The virus can infect humans, birds, mosquitoes, horses and some other mammals.
"West Nile fever is a case of mild disease in people, characterized by flu-like symptoms. West Nile fever typically lasts only a few days and does not appear to cause any long-term health effects.
More severe disease due to a person being infected with this virus can be "West Nile encephalitis," West Nile meningitis or West Nile meningoencephalitis." Encephalitis refers to an inflammation of the brain, meningitis is an inflammation of the membrane around the brain and the spinal cord, and meningoencephalitis refers to inflammation of the brain and the membrane surrounding it.
Q. Where did West Nile virus come from?
A. West Nile virus has been commonly found in humans and birds and other vertebrates in Africa, Eastern Europe, West Asia, and the Middle East, but until 1999 had not previously been documented in the Western Hemisphere. It is not known from where the U.S. virus originated, but it is most closely related genetically to strains found in the Middle East.
Q. Historically, where has West Nile encephalitis occurred worldwide?
A. See the map describing distribution of flaviviruses, including West Nile virus:
Q. How long has West Nile virus been in the U.S.?
A. It is not known how long it has been in the U.S., but CDC scientists believe the virus has probably been in the eastern U.S. since the early summer of 1999, possibly longer.
Q. I understand West Nile virus was found in "overwintering" mosquitoes in the New York City area in early 2000. What does this mean?
A. One of the species of mosquitoes found to carry West Nile virus is the Culex species which survive through the winter, or "overwinter," in the adult stage. That the virus survived along with the mosquitoes was documented by the widespread transmission the summer of 2000.
Q. Is West Nile virus now established in the Western Hemisphere?
A. The continued expansion of West Nile virus in the United States indicates that it is permanently established in the Western Hemisphere.
Q. Is the disease seasonal in its occurrence?
A. In the temperate zone of the world (i.e., between latitudes 23.5° and 66.5° north and south), West Nile encephalitis cases occur primarily in the late summer or early fall. In the southern climates where temperatures are milder, West Nile virus can be transmitted year round.
Symptoms of West Nile Virus
Q. Who is at risk for getting West Nile encephalitis?
A. All residents of areas where virus activity has been identified are at risk of getting West Nile encephalitis; persons over 50 years of age have the highest risk of severe disease. It is unknown if immunocompromised persons are at increased risk for WNV disease.
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.
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.
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.
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.
Cases of West Nile Encephalitis
Q. How many cases of West Nile disease in humans have occurred in the U.S.?
A.
Year Human Cases Human Deaths
1999 62 7
2000 21 2
2001 66 9
2002 4,161 277
2003 9,122 223
No reliable estimates are available for the number of cases of West Nile encephalitis that occur worldwide.
Q. What proportion of people with severe illness due to West Nile virus die?
A. Among those with severe illness due to West Nile virus, case-fatality rates range from 3% to 15% and are highest among the elderly. Less than 1% of persons infected with West Nile virus will develop severe illness.
Testing and Treating West Nile Encephalitis in Humans
Q. I think I have symptoms of West Nile virus. What should I do?
A. Contact your health care provider if you have concerns about your health. If you or your family members develop symptoms such as high fever, confusion, muscle weakness, and severe headaches, you should see your doctor immediately.
Q. How do health care providers test for West Nile virus?
A. Your physician will first take a medical history to assess your risk for West Nile virus. People who live in or traveled to areas where West Nile virus activity has been identified are at risk of getting West Nile encephalitis; persons older than 50 years of age have the highest risk of severe disease. If you are determined to be at high risk and have symptoms of West Nile encephalitis, your provider will draw a blood sample and send it to a commercial or public health laboratory for confirmation.
Q. How is West Nile encephalitis treated?
A. There is no specific treatment for West Nile virus infection. In more severe cases, intensive supportive therapy is indicated, often involving hospitalization, intravenous fluids, airway management, respiratory support (ventilator), prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.
West Nile Virus and Breast-feeding
Q. Can West Nile virus be transmitted through breast milk?
A. Based on a recent case in Michigan, it appears that West Nile virus can be transmitted through breast milk. A new mother in Michigan contracted West Nile virus from a blood transfusion shortly after giving birth. Laboratory analysis showed evidence of West Nile virus in her breast milk. She breastfed her infant, and three weeks later, her baby's blood tested positive for West Nile virus. Because of the infant's minimal outdoor exposure, it is unlikely that infection was acquired from a mosquito. The infant was most likely infected through breast milk. The child is healthy, and does not have symptoms of West Nile virus.
Q. Should I continue breast-feeding if I am symptomatic for West Nile virus?
A. Because the health benefits of breast-feeding are well established, and the risk for West Nile virus transmission through breast-feeding is unknown, the new findings do not suggest a change in breast-feeding recommendations. The American Academy of Pediatricians and the American Academy of Family Physicians recommend that infants be breastfed for a full year of life.
Lactating women who are ill or who are having difficulty breast-feeding for any reason, as always, should consult their physicians.
Q. Should I continue breast-feeding if I am not symptomatic for West Nile virus?
A. Yes. Because the health benefits of breast-feeding are well established, and the risk for West Nile virus transmission through breast-feeding is unknown, the new findings do not suggest a change in breast-feeding recommendations.
Q. If I am breast-feeding, should I be tested for West Nile virus?
A. No. There is no need to be tested just because you are breast-feeding.
Q. Are infants at higher risk than other groups for illness with West Nile virus?
A. No. West Nile virus illnesses in children younger than 1-year-old are infrequent. During 1999-2001, no cases in children younger than one year of age were reported to CDC. Of the over 2500 total West Nile Virus cases in 2002, only four were less than one year of age. We know that one of these infants was not breast-feeding, and investigation of the other infants is underway.
Q. If I am breast-feeding, should I use insect repellent containing DEET?
A. Yes. 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. There are no reported adverse events following use of repellents containing DEET in pregnant or breast-feeding women.
Transmission
Q. How do people get infected with West Nile virus (WNV)?
A. The principle route of human infection with West Nile virus is through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. The virus eventually finds its way into the mosquito's salivary glands. During subsequent blood meals, the virus may be injected into humans and animals, where it can multiply and possibly cause illness.
Additional routes of infection have become apparent during the 2002 West Nile epidemic. It is important to note that these other methods of transmission represent a very small proportion of cases. A recent investigation has confirmed WNV transmission through transplanted organs. Investigations of other patients who developed WNV infection within several weeks of receiving blood products or organs are ongoing to determine whether WNV was transmitted by transfusion or transplantation in any of these cases.
There is one reported case of transplacental (mother-to-child) WNV transmission. This case is detailed in MMWR Dec 20, 2002. Although transmission of WNV and similar viruses to laboratory workers is not a new phenomenon, two recent cases of WNV infection of laboratory workers have been reported. These cases are detailed in MMWR Dec 20, 2002.
Q. What is the basic transmission cycle of West Nile virus?
A. Mosquitoes become infected when they feed on infected birds, which may circulate the virus in their blood for a few days. Infected mosquitoes can then transmit West Nile virus to humans and animals while biting to take blood. The virus is located in the mosquito's salivary glands. During blood feeding, the virus may be injected into the animal or human, where it may multiply, possibly causing illness.
Q. If I live in an area where birds or mosquitoes with West Nile virus have been reported and a mosquito bites me, am I likely to get sick?
A. No. Even in areas where the virus is circulating, very few mosquitoes are infected with the virus. Even if the mosquito is infected, less than 1% of people who get bitten and become infected will get severely ill. The chances you will become severely ill from any one mosquito bite are extremely small.
Q. Can you get West Nile encephalitis from another person?
A. No. West Nile encephalitis is NOT transmitted from person-to-person. For example, you cannot get West Nile virus from touching or kissing a person who has the disease, or from a health care worker who has treated someone with the disease.
Q. Is a woman's pregnancy at risk if she gets infected with West Nile virus?
A. There is one documented case of transplacental (mother-to-child) transmission of WNV in humans. Although the newborn in this case was infected with WNV at birth and had severe medical problems, it is unknown whether the WNV infection itself caused these problems or whether they were coincidental. More research will be needed to improve our understanding of the relationship - if any - between WNV infection and adverse birth outcomes.
Nevertheless, pregnant women should take precautions to reduce their risk for WNV and other arboviral infections by avoiding mosquitoes, using protective clothing and repellents containing DEET (See Using Repellents Safely) When WNV transmission is occurring in an area, pregnant women who become ill should see their health care provider. Those whose illness is consistent with acute WNV infection (see Symptoms) should undergo appropriate diagnostic testing.
For more details regarding the case described above, please see: MMWR Dec 20, 2002.
Q. Can West Nile virus be transmitted through blood transfusions?
A. Please refer to Blood Transfusions and Transmission: Questions and Answers.
Q. Are laboratory workers in contact with WNV-positive specimens at risk for WNV infection?
A. Yes, and approximately 20 laboratory-acquired WNV infections have been reported in the medical literature over many decades. In the two most recently reported cases, WNV infection of two microbiologists working with WNV-positive samples resulted from percutaneous inoculation (pierced through the skin). Both persons had mild, self-limited illnesses.
As more laboratories are have recently become involved in WNV diagnostic and reference activities, the risk for laboratory acquired WNV infections has probably increased. Laboratory workers handling materials that are potentially infected with WNV should use every precaution to minimize their risk for exposure. For more details, please see: MMWR, Dec 20, 2002.
Q. Besides mosquitoes, can you get West Nile virus directly from other insects or ticks?
A. Infected mosquitoes are the primary source for West Nile virus. Although ticks infected with West Nile virus have been found in Asia and Africa, their role in the transmission and maintenance of the virus is uncertain. However, there is no information to suggest that ticks played any role in the cases identified in the United States.
Q. How many types of animals have been found to be infected with West Nile virus?
A. Although the vast majority of infections have been identified in birds, WN virus has been shown to infect horses, cats, bats, chipmunks, skunks, squirrels, and domestic rabbits.
Q. Can you get West Nile virus directly from birds?
A. There is no evidence that a person can get the virus from handling live or dead infected birds. However, persons should avoid bare-handed contact when handling any dead animals and use gloves or double plastic bags to place the carcass in a garbage can.
Q. Can you get infected with West Nile virus by caring for an infected horse?
A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of West Nile virus. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
Q. Can you get WNV from eating game birds or animals that have been infected?
A. There is no evidence that WNV virus can be transmitted to humans through consuming infected birds or animals. In keeping with overall public health practice, and due to the risk of known food-borne pathogens, people should always follow procedures for fully cooking meat from either birds or mammals.
Q. How does West Nile virus actually cause severe illness and death in humans?
A. Following transmission by an infected mosquito, West Nile virus multiplies in the person's blood system and crosses the blood-brain barrier to reach the brain. The virus interferes with normal central nervous system functioning and causes inflammation of brain tissue.
Q. How long does the West Nile virus remain in a person's body after they are infected?
A. There is no scientific evidence indicating that people can be chronically infected with West Nile virus. What remain in a person’s body for long periods of time are antibodies and "memory" white blood cells (T-lymphocytes) that the body produces to the virus. These antibodies and T-lymphocytes last for years, and may last for the rest of a person’s life. Antibodies are what many diagnostic tests look for when clinical laboratories testing is performed. Both antibodies and "memory" T-lymphocytes provide future protection from the virus.
Q. If a person contracts West Nile virus, does that person develop a natural immunity to future infection by the virus?
A. It is assumed that immunity will be lifelong; however, it may wane in later years.
Blood Transfusions and Organ Donations
Q. Is West Nile virus (WNV) transmitted by blood transfusion or organ donation?
A. A recent investigation has identified transplanted organs as the source of WNV infection in four recipients of organs from a single donor. How the organ donor became infected is unknown. The organ donor might have become infected from a mosquito bite or possibly acquired the infection through transfusion; an investigation of the numerous transfusions received by the organ donor is ongoing. Since the report of these cases, CDC has been informed of other patients who developed WNV infection within several weeks of receiving blood products or organs. Investigations are ongoing to determine whether WNV was transmitted by transfusion or transplantation in any of these cases.
Q. What is being done about the possibility of transfusion-related WNV transmission?
A. CDC, FDA, blood collection agencies, and state and local health departments are investigating possible cases of WNV transmission through blood transfusion and organ transplantation. For cases currently under investigation, any remaining blood products from donors whose blood was transfused to patients with confirmed or suspected WNV infection have been withdrawn and efforts are underway to contact these donors as well as other recipients of blood products from these donors for follow up.
As part of the investigation, CDC has asked that physicians notify public health authorities of any patients who develop symptoms of WNV infection within 4 weeks of receiving a blood transfusion or organ transplantation. In addition, patients with WNV infection whose symptoms begin in the weeks preceding blood or organ donation should also be reported. Prompt reporting of these persons will help facilitate withdrawal of potentially infected blood components.
Q. Should people avoid donating blood or getting blood transfusions or organ transplants?
A. Blood is lifesaving and is currently in short supply. Donating blood is safe, and we encourage blood donation now and in the future. Approximately 4.5 million persons receive blood or blood products annually. Although persons needing blood transfusions or organ transplants should be aware of the risk for WNV infection, the benefits of receiving needed transfusions or transplants outweigh the potential risk for WNV infection.
Q. How can blood banks avoid collecting blood from donors who may have West Nile virus?
A. On August 17, FDA issued an alert to blood banks and organizations to be vigilant in excluding individuals who may have early symptoms of West Nile virus from donating blood. Most people who have West Nile virus do not show symptoms, making it difficult to defer them from donation. However, some individuals develop minor symptoms of fever and headache. Blood banks need to be vigilant to defer all of those who may have minor illnesses, especially in areas where West Nile virus is most active.
Q. If a person has had West Nile virus, can they still donate blood?
A. With West Nile virus infection, the viremia usually is transient, and people clear the virus very quickly. Blood centers will take precautions (see preceding question and answer) to be sure that donors who have been diagnosed with West Nile virus have fully recovered before donating.
Q. If I recently had a transfusion or transplant, should I be concerned about getting West Nile virus?
A. You should be aware of the potential risk for WNV infection and the need to monitor your health. If you have symptoms of West Nile virus or other concerns you should contact your physician. However, it is important to remember that a large number of WNV infections due to mosquito bites have occurred among persons in the United States this year. By chance alone, some of these persons will have received blood transfusions and/or organ transplantations. Recent receipt of a blood transfusion or organ transplantation by a person with WNV infection does not necessarily implicate the transfusion/transplantation as the source of infection.
Prevention
Q. What can I do to reduce my risk of becoming infected with West Nile virus?
A. 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 and Safety questions.
- 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.
Note: Vitamin B and "ultrasonic" devices are NOT effective in preventing mosquito bites.
New! Kids can learn how to protect themselves from mosquito bites on "The Buzz-z-z-z on West Nile Virus" (on BAM!, the CDC site for kids).
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. Details about effective prevention and control of West Nile virus can be found in CDC's Guidelines for Surveillance, Prevention, and Control(286 KB, 111 pages).
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 and Safety
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. (For more information, see Table 1: Fradin and Day, 2002. See Publications page.)
Q. Why does CDC recommend using DEET?
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.(Fradin and Day, 2002. See Publications page.)
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%) (Fradin and Day, 2002. See Publications page.).
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-diethly-3-methylbenamide. 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. (From the National Pesticide Information Center [NPIC], EPA re-registration eligibility decision. See http://npic.orst.edu/factsheets/DEETgen.pdf
.)
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. No serious illness has arisen from use of DEET when used according the manufacturer’s recommendations. 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.
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. Children and adults can wear clothing with long pants and long sleeves while outdoors. DEET or other repellents such as permethrin can also be applied to clothing (don’t use permethrin on skin), as mosquitoes may bite through thin fabric. Mosquito netting can be used over infant carriers. Finally, it may be possible to reduce the number of mosquitoes in the area by getting rid of containers with standing water that provide breeding places for the mosquitoes.
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.
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
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/index.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.
West Nile Virus and Birds
Q. Do birds infected with West Nile virus die or become ill?
A. In the 1999 New York area epidemic, there was a large die-off of American crows. Since then, West Nile virus has been identified in more than 100 species of birds found dead in the United States. Most of these birds were identified through reporting of dead birds by the public.
Q. How can I report a sighting of dead bird(s) in my area?
A. State and local health departments may start collecting reports of dead birds at different times in the year. Some wait until the weather becomes warm before initiating their surveillance program. For information about reporting dead birds in your specific area, please contact your state or local health department.
Q. Why have some areas stopped collecting dead birds?
A. Some states and jurisdictions are no longer collecting dead birds because they have sufficiently established that the virus is in an area, and additional testing will not reveal any more information. Shifting resources away from testing of dead birds allows those resources to be devoted elsewhere in surveillance and control.
West Nile Virus and Horses
Q. Has West Nile virus caused severe illness or death in horses?
A. Yes, while data suggest that most horses infected with West Nile virus recover, results of investigations indicate that West Nile virus has caused deaths in horses in the United States. In 2003, there were 4,636 deaths.
Q. How do the horses become infected with West Nile virus?
A. The same way humans become infected—by the bite of infectious mosquitoes. The virus is located in the mosquito's salivary glands. When mosquitoes bite or "feed" on the horse, the virus is injected into its blood system. The virus then multiplies and may cause illness. The mosquitoes become infected when they feed on infected birds or other animals.
Q. How does the virus cause severe illness or death in horses?
A. Following transmission by an infected mosquito, West Nile virus multiplies in the horse's blood system, crosses the blood brain barrier, and infects the brain. The virus interferes with normal central nervous system functioning and causes inflammation of the brain.
Q. Can I get infected with West Nile virus by caring for an infected horse?
A. West Nile virus is transmitted by infectious mosquitoes. There is no documented evidence of person-to-person or animal-to-person transmission of West Nile virus. Normal veterinary infection control precautions should be followed when caring for a horse suspected to have this or any viral infection.
Q. Can a horse infected with West Nile virus infect horses in neighboring stalls?
A. No. There is no documented evidence that West Nile virus is transmitted between horses. However, horses with suspected West Nile virus should be isolated from mosquito bites, if at all possible.
Q. My horse is vaccinated against eastern equine encephalitis (EEE), western equine encephalitis (WEE), and Venezuelan equine encephalitis (VEE). Will these vaccines protect my horse against West Nile virus infection?
A. No. EEE, WEE, and VEE belong to another family of viruses for which there is no cross-protection.
Q. Can I vaccinate my horse against West Nile virus infection?
A. A West Nile virus vaccine for horses was recently approved, but its effectiveness is unknown.
Q. How long will a horse infected with West Nile virus be infectious?
A. We do not know if an infected horse can be infectious (i.e., cause mosquitoes feeding on it to become infected). However, previously published data suggest that the virus is detectable in the blood for only a few days.
Q. What is the treatment for a horse infected with West Nile virus? Should it be destroyed?
A. There is no reason to destroy a horse just because it has been infected with West Nile virus. Data suggest that most horses recover from the infection. Treatment would be supportive and consistent with standard veterinary practices for animals infected with a viral agent.
Q. Where can I get more information on horses and West Nile virus?
A. Visit the USDA Web site Animal and Plant Health Inspection Service (APHIS).
West Nile Virus and Squirrels
Q. Can squirrels infected with West Nile virus transmit the virus to humans?
A. A small number of squirrels have tested positive for the West Nile virus. There is no evidence that people could become infected with the West Nile virus by being near an infected squirrel or in the yard with a dead one. However, the presence of an infected squirrel does mean that there could be infected mosquitoes nearby, and people should use protective clothing and repellent, and avoid maintaining mosquito-breeding sites on their property.
West Nile Virus and Wild Game Hunters
Q. Are duck and other wild game hunters at risk for West Nile virus infection?
A. Because of their outdoor exposure, game hunters may be at risk if they become bitten by mosquitoes in areas with West Nile virus activity. The extent to which West Nile virus may be present in wild game is unknown.
Q. What should wild game hunters do to protect against West Nile virus infection?
A. Hunters should follow the usual precautions when handling wild animals. If they anticipate being exposed to mosquitoes, they should apply insect repellents to clothing and skin, according to label instructions, to prevent mosquito bites. Hunters should wear gloves when handling and cleaning animals to prevent blood exposure to bare hands and meat should be cooked thoroughly.
Q. Who should wild game hunters contact for information about the risk for West Nile virus infection in specific geographic areas?
A. Hunters should check with their local area department of wildlife and naturalist resources, state epidemiologist at the state health department, or the US Geological Survey (USGS) National Wildlife Health Center, Madison, WI, 608-270-2400 for information on local area risk
Last updated: 8/3/09 4:52 PM
