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Medical Conditions

Mosquito-borne Diseases

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What are mosquito-borne diseases?

  • Diseases spread by infected mosquitoes—in the United States, most are caused by viruses.

  • Examples of viruses spread by mosquitoes include West Nile virus, eastern equine encephalomyelitis (EEE), St. Louis encephalitis (SLE), La Crosse encephalitis, western equine encephalomyelitis (WEE), dengue, chikungunya, and Zika.

  • West Nile virus and EEE are discussed in detail because they get the most media attention; however, in children, most of these infections produce no signs or symptoms or mild headache and fever. In outbreaks, more severe illness (including central nervous system involvement) can occur, especially among adults.

  • Malaria is a mosquito-borne disease caused by a parasite that occurs commonly in tropical areas of the world. It is extremely uncommon in the United States, except among international travelers

  • Dengue and chikungunya are mosquito-borne viruses that have recently been introduced into the United States. Dengue has caused illness in certain southern states in the past 2 to 3 years and is common in Puerto Rico, the Virgin Islands, and American Samoa, where children may vacation with parents. Chikungunya is another recent virus spread by mosquitos that has come to the United States. There were more than 1,500 cases in the United States in 2014.

  • Zika is a mosquito-borne disease that usually causes mild illness that lasts from several days to a week. Outbreaks of Zika have occurred in Africa, Southeast Asia, the Pacific Islands, and the Americas. The mosquito that spreads Zika virus is everywhere in the world. So it is likely the Zika virus will spread to new countries, including the continental United States. So far, the reports are from Puerto Rico and from returning travelers from countries where Zika is already occurring. Information and recommendations regarding Zika are rapidly evolving at the time of this writing. Please visit the CDC Zika updates page for the most recent information: http://www.cdc.gov/zika/index.html. When Zika virus infects a pregnant woman, it can spread to her unborn baby. Researchers are investigating the evidence that infection with this virus is associated with problems with pregnancy and damage to the baby. The Centers for Disease Control and Prevention (CDC) recommends pregnant women consider putting off travel to areas where Zika virus is spreading, use repellents and other measures to avoid mosquito bites if they do travel to these areas, and use condoms for sexual activity of any type while pregnant.

What are the signs or symptoms?

  • Many people have few signs or symptoms.

  • Fever.

  • Headache.

  • Body aches.

  • Nausea.

  • Vomiting.

  • Rash.

  • Convulsions.

  • Coma.

  • Paralysis (in West Nile disease, paralysis of the facial muscles [Bell palsy] has been noted).

  • Joint pain and conjunctivitis (pinkeye [conjunctivitis] or red eyes) for Zika.

What are the incubation and contagious periods?

  • Incubation periods

    — West Nile virus 2 to 14 days
    — EEE 3 to 10 days
    — SLE 4 to 14 days
    — La Crosse encephalitis 5 to 15 days
    — WEE 2 to 10 days

  • Contagious period: These infections are not contagious.

How are they spread?

Through the bite of an infected mosquito. West Nile virus may also be spread by blood transfusion and organ donation.

How do you control them?

  • By avoiding mosquito bites and getting rid of standing water where mosquitoes lay their eggs.

  • Do not wear products that have an odor. They attract mosquitoes.

  • Protect the skin by wearing clothing that puts a barrier over the skin, like long sleeves, long pants, socks, shoes, and hats.

  • Use insect repellents containing diethyltoluamide (DEET). Repellents make the user unattractive to mosquitoes. They do not kill the insects.

    • DEET is safe and is the most studied and effective mosquito repellent. Generally, higher concentrations of DEET provide longer protection times, but concentrations of more than 50% provide minimal additional benefit. The CDC recommends 20% to 30% DEET concentrations, which provide at least 3 hours of protection.

    • DEET should not be used in a product that combines the repellent with a sunscreen. Sunscreens are often applied repeatedly because they can be washed off. DEET is not water-soluble and will last up to 8 hours. Repeated application of this combination product may increase the potential toxic effects of DEET.

    • DEET may be applied to exposed intact skin according to CDC instructions (www.cdc.gov/westnile/faq/ repellent.html) and the US Environmental Protection Agency (EPA) (www.epa.gov/insect-repellents/deet).

    • Apply DEET sparingly on exposed skin; do not use under clothing. If repellent is applied to clothing, wash or dry-clean treated clothing before wearing again.

    • Do not use DEET on the hands of young children; avoid getting DEET in the eyes and mouth, as DEET irritates these tissues.

    • Do not use DEET over cuts, wounds, or irritated skin. Wash treated skin with soap and water after returning indoors; wash treated clothing.

    • Avoid spraying in enclosed areas; do not use DEET near food.

    • Do not use DEET in infants younger than 2 months.

  • Non-DEET products containing icaridin or picaridin and IR3535 have been shown to be effective mosquito repellents, although less so than DEET. Some plant-based products, such as oil of lemon, eucalyptus, and citronella, show some benefit, although also not as effective as DEET.

  • Many other products claim they prevent mosquito bites, but objective evaluation of them finds they are of little or no value. Among the products that have been found to be ineffective in objective tests are catnip oil, essential plant oils, garlic, vitamin B1, wearing sound-producing devices, or wearing impregnated wrist bands.

  • Mosquito traps, bug zappers, ultrasonic repellers, and other devices to prevent mosquito bites are not very effective. Spatial repellent devices that release a repellent material into an area in the form of a vapor are becoming widely available. These products release volatile active ingredients, such as pest repellants metofluthrin and allethrin, and are approved by the EPA for use outdoors. Although many of these products have documented repellent activity, their ability to provide protection from mosquito bites has not been evaluated thoroughly.

  • If possible, stay inside during dusk and dawn, when mosquitoes are most active. When outside at these times, wear long sleeves and long pants.

  • Check windows to make sure there are no holes in the screens to allow mosquitoes to get indoors.

  • Empty or remove standing water from wading pools, buckets, pet dishes, flowerpots, areas where gutter drains leave standing water, and other sources that can attract mosquitoes.

  • Some mosquitoes that spread certain viral diseases are active during the day (eg, Zika virus, which seems to be able to damage a pregnant woman’s unborn baby). Where Zika is known to be spreading, pregnant women should use the measures described to prevent mosquito bites at any time of day.

What are the roles of the teacher/caregiver and the family?

  • Follow public health recommendations about preventing mosquito bites.

  • Share information about the disease.

Exclude from group setting?

No, unless

  • The child is unable to participate and staff members determine they cannot care for the child without compromising their ability to care for the health and safety of the other children in the group.

  • The child meets other exclusion criteria.

Readmit to group setting?

Yes, when all the following criteria have been met:

When exclusion criteria are resolved, the child is able to participate, and staff members determine they can care for the child without compromising their ability to care for the health and safety of the other children in the group


  • Mosquitoes become infected with West Nile virus after biting infected birds. If you find a dead bird (especially blue jays, crows, or wrens), report it to your local health department and ask for instructions on disposing of the bird’s body. Do not handle the body with your bare hands.

  • Most cases of mosquito-borne infection are caused by West Nile virus. West Nile virus infections in children are usually mild.

Listing of resources does not imply an endorsement by the American Academy of Pediatrics (AAP). The AAP is not responsible for the content of external resources. Information was current at the time of publication.

The information contained in this publication should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.

Quick Reference Sheet from Managing Infectious Diseases in Child Care and Schools: A Quick Reference Guide.

© 2017 American Academy of Pediatrics. All rights reserved.