What to Know About Mosquito-Borne Diseases

With the U.S. in peak mosquito season, health officials are warning people to take extra precautions against mosquito-borne diseases. While the risk of becoming seriously ill from a mosquito bite is low, it can happen.

Every year, cases of West Nile virus are reported across the country. As of this week, 33 states have reported human cases of West Nile, according to the Centers for Disease Control and Prevention (CDC), and Dr. Anthony Fauci, the nation’s former top infectious disease expert, recently shared he is recovering after being hospitalized from the virus. In addition, rare cases of Eastern equine encephalitis (EEE) in the Northeast have prompted some health officials to close public parks from dusk until dawn when the mosquitoes are most active.

“Mosquito bites can be more than a mere annoyance, so it’s important to focus on deterring mosquitoes and preventing bites,” says Dr. Laura Kirkman, an infectious disease doctor at NewYork-Presbyterian/Weill Cornell Medical Center. “Apply mosquito repellant before you go outside and consider wearing clothes that will keep the bugs away, like long sleeves or light pants. If you have a baby under 2 months old, you can put mosquito netting or a light blanket over the stroller.”

Dr. Kirkman shared more with Health Matters about mosquito-borne diseases, including why mosquitoes bite, and what to do if you get bitten.

How worried should we be about West Nile virus?
Dr. Kirkman: West Nile virus is the most common mosquito-borne disease in the U.S. It is seen all over the country, including urban areas, because the mosquitoes that carry it can thrive in any stagnant water. Most people — approximately 80% — who get infected do not develop symptoms, but for those that do it can be quite serious and require medical care.

There is no person-to-person transmission of West Nile. Mosquitoes carry the virus to humans after they bite a bird or another animal. Also, there are no vaccines, so bite prevention is the only way to avoid infection.

What about Eastern equine encephalitis?
Eastern equine encephalitis (EEE) is more often seen closer to forested wetland or swamp environments, primarily in the Southeast, Northeast and the Great Lakes regions. It is transmitted by a different kind of mosquito which likes to live mostly around bogs and swamps.

EEE is rare, but it can be quite serious. There have been sporadic cases every year with periodic outbreaks that drive up the numbers. Like West Nile, mosquitos that feed on birds and other animals are the ones transmitting EEE — it is not contagious from person to person. And taking precautions to prevent bites is the best way to stay safe because there are no vaccines.

What are the symptoms of West Nile or EEE?
The vast majority of people who are bitten by a mosquito with West Nile or EEE will not become seriously ill.

People who do become ill will start to have symptoms four to 15 days after a bite. The early signs are fever, chills, headache, and muscle and joint aches. The more worrisome symptoms are seizures, behavioral changes, drowsiness and coma, which could mean that the virus has moved into the central nervous system and can cause encephalitis or meningitis (inflammation of the membrane around the brain or of the spinal cord). But this is extremely rare.

What normally happens after a mosquito bites you?
When mosquitoes probe around in your skin, they’re putting saliva into your body, and you react to the protein in the saliva. Usually a puffy and red bump will appear a few minutes after the bite. How big the welt is varies from person to person, especially because some people have allergic reactions. If the welt continues to get bigger, redder, and hot after five to seven days, it could be a sign of a bacterial infection called cellulitis, and antibiotics might be needed to treat it.

Which repellents do you recommend?
Most of the products you find in the store contain DEET or picaridin. Both are safe to use. The sprays work for ticks as well, so if you live in an area with ticks, it’s doubly beneficial. You can learn more about different repellents through the Environmental Protection Agency (EPA) search tool. There’s a lot of fear about repellents, particularly with DEET, but if you don’t apply them when you go outside, you are going to have an increased risk of bug bites. Try to stick to the EPA-approved repellants so that you can have long-lasting protection.

What other advice do you have for reducing risk when it comes to mosquitoes?
Eliminating standing water around your home — for example in birdbaths or empty planters — is a good idea, as it can serve as a breeding ground for mosquitoes. Using screened windows and doors is also very important.

What is the best way to treat a mosquito bite?
Most mosquito bites will swell and itch for a day or two and then get better over time. Try not to scratch them, as you do not want to break the skin. To reduce the swelling, apply an ice pack to the site, and for itching, a mixture of baking soda and water will help, or you can apply an over-the-counter anti-itch or antihistamine cream.

Is it true that some people are mosquito magnets?
There is scientific evidence that mosquitoes are drawn to certain chemicals present in human body odor. A significant new study on the African malaria mosquito found that mosquitoes are sensitive to the scent of organic compounds on the skin. The study also found that mosquitoes are repelled by eucalyptol, which is present in a variety of plants we eat (for example, rosemary, sage, and cardamom), toothpaste, and cough medicines. However, eucalyptol is not the optimal repellant. To prevent bites, use the EPA-approved repellants and other prevention methods like staying indoors during prime biting hours.