St. Louis encephalitis (SLE) virus is spread to people primarily through the bite of an infected mosquito. Mosquitoes bite during the day and night. There is no vaccine to prevent SLE virus infection. The best way to prevent SLE is to protect yourself from mosquito bites. Use insect repellent, wear long-sleeved shirts and pants, treat clothing and gear, and take steps to control mosquitoes indoors and outdoors.
Protect Yourself and Your Family from Mosquito Bites
Use insect repellent
Use Environmental Protection Agency (EPA)-registered insect repellents with one of the active ingredients below. When used as directed, EPA-registered insect repellents are proven safe and effective, even for pregnant and breastfeeding women.
- Picaridin (known as KBR 3023 and icaridin outside the US)
- Oil of lemon eucalyptus (OLE)
- Para-menthane-diol (PMD)
Find the right insect repellent for you by using EPA’s search tool.
Tips for babies and children
- Dress your child in clothing that covers arms and legs.
- Cover strollers and baby carriers with mosquito netting.
- When using insect repellent on your child:
- Always follow label instructions.
- Do not use products containing oil of lemon eucalyptus (OLE) or para-menthane-diol (PMD) on children under 3 years old.
- Do not apply insect repellent to a child’s hands, eyes, mouth, cuts, or irritated skin.
- Adults: Spray insect repellent onto your hands and then apply to a child’s face.
Tips for everyone
- Always follow the product label instructions.
- Reapply insect repellent as directed.
- Do not spray repellent on the skin under clothing.
- If you are also using sunscreen, apply sunscreen first and insect repellent second.
Natural insect repellents (repellents not registered with EPA)
- We do not know the effectiveness of non-EPA registered insect repellents, including some natural repellents.
- To protect yourself against diseases spread by mosquitoes, CDC and EPA recommend using an EPA-registered insect repellent.
- Choosing an EPA-registered repellent ensures the EPA has evaluated the product for effectiveness.
- Visit the EPA website to learn more.
Wear loose-fitting, long-sleeved shirts and pants
Treat clothing and gear
- Use 0.5% permethrin to treat clothing and gear (such as boots, pants, socks, and tents) or buy permethrin-treated clothing and gear.
- Permethrin is an insecticide that kills or repels mosquitoes.
- Permethrin-treated clothing provides protection after multiple washings.
- Read product information to find out how long the protection will last.
- If treating items yourself, follow the product instructions.
- Do not use permethrin products directly on skin.
- Watch the video, What You Need to Know About Permethrin.
Take steps to control mosquitoes indoors and outdoors
- Use screens on windows and doors. Repair holes in screens to keep mosquitoes outdoors.
- Use air conditioning, if available.
- Stop mosquitoes from laying eggs in or near water.
- Once a week, empty and scrub, turn over, cover, or throw out items that hold water, such as tires, buckets, planters, toys, pools, birdbaths, flowerpots, or trash containers.
- Check for water-holding containers both indoors and outdoors.
Prevent Mosquito Bites When Traveling Overseas
Remember to pack the following items
- EPA-registered insect repellentsexternalexternal
- Long-sleeved shirts and long pants. Mosquitoes may bite through thin clothing.
- Clothing and gear (such as boots, pants, socks, tents) treated with 0.5% permethrin. You can treat your own items or purchase permethrin-treated clothing and gear.
- Mosquito net if you will be sleeping outside or when screened rooms are not available.
Keep mosquitoes out of your hotel room or lodging
- Choose a hotel or lodging with air conditioning or window and door screens.
- Use a mosquito net if you are unable to stay in a place with air conditioning or window and door screens or if you are sleeping outside.
Sleep under a mosquito net
Sleep under a mosquito net if you are outside or when screened rooms are not available. Mosquitoes can live indoors and bite during the day and night.
- Buy a mosquito net at your local outdoor store or online before traveling overseas.
- Choose a mosquito net that is compact, white, rectangular, with 156 holes per square inch, and long enough to tuck under the mattress.
- Permethrin-treated mosquito nets provide more protection than untreated nets.
- Permethrin is an insecticide that kills mosquitoes and other insects.
- To determine if you can wash a treated mosquito net, follow the label instructions.
Use mosquito nets correctly
Mosquito nets can be hung above a bed or crib to protect against mosquito bites. Adults and children should sleep under a mosquito net if air conditioned and screened rooms are not available.
When using a mosquito net:
- Tuck the net under the mattress to keep the mosquitoes out.
- Tuck netting under the crib mattress or select a mosquito net long enough to touch the floor.
- Pull the net tightly to avoid choking hazards for young children. Check label instructions for additional information.
- Hook or tie the sides of the net to other objects if they are sagging in towards the sleeping area.
- Check for holes or tears in the net where mosquitoes can enter.
- DO NOT hang the net near any candles, cigarettes, or open fires, as it can catch on fire.
- DO NOT sleep directly against the net, as mosquitoes can still bite through holes in the net.