A man opening a mosquito net.Share on Pinterest
As temperatures heat up and mosquitoes multiply, it’s important to be aware of the potential health risks of mosquito-borne illnesses. Chalffy/Getty Images
  • Mosquitoes can carry viruses or parasites that cause a number of diseases in people.
  • In the U.S., mosquito-borne diseases like West Nile virus are common, but most cases are mild.
  • The best way to protect yourself against West Nile virus and other mosquito-borne illnesses is to avoid getting bitten by mosquitoes.

More than just a nuisance, mosquitoes can spread disease. When mosquitoes bite and drink blood from a person or animal, they can pick up a virus or parasite. If they bite another person or animal, they can pass on that microbe.

Over 200 types of mosquitoes live in the continental United States and U.S. territories, yet only about 12 can spread a virus or parasite that makes people sick, such as West Nile virus disease.

“Most mosquito bites are not going to result in West Nile virus because the vast majority of mosquitoes are not infected with West Nile virus,” said Marc Siegel, MD, a professor of medicine in the Division of Infectious Diseases at the George Washington School of Medicine and Health Sciences.

Climate change, though, has led to a rise in mosquito-borne illnesses in other parts of the world, which will increase human exposure to these diseases.

As temperatures heat up and mosquitoes multiply, it’s important to be aware of the potential health risks of mosquito-borne illnesses and take precautions to avoid getting bitten.

“Minimizing excessive mosquito exposure is probably the only thing people can do to protect themselves,” Siegel told Healthline. “So avoid the times that mosquitoes tend to feed more, which is dusk to dawn.

If you do have to be outside, Siegel said, wear pants and a long-sleeved shirt or jacket and mosquito repellent, especially in wooded or swampy areas.

Here’s what you need to know about the four most common types of mosquito-borne illnesses, the risks they can pose, and how to protect yourself.

Birds are the natural hosts of West Nile virus. Mosquitoes that become infected by biting and drawing blood from a bird can pass on the virus when they bite a person.

West Nile virus disease is the most common mosquito-borne illness in the United States. Its season typically runs from June through September.

Mosquito-borne illnesses like West Nile are currently low, but they may increase later this summer.

As of June 17, the Centers for Disease Control and Prevention (CDC) reports just 16 human cases of West Nile virus disease. So far, 11 states have confirmed West Nile cases, mostly in the Southeastern U.S., such as Louisiana, with other cases recently confirmed in the Midwest, such as Illinois.

While as many as 1 in 5 people who contract West Nile virus may develop symptoms like fever or headache, more serious or fatal outcomes are less common, affecting around 1 in 150 people.

“There are probably a higher number of total infections, many of which are not diagnosed,” said David Sullivan, a professor in the Department of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health.

However, “this is still less than the chance of being hit by lightning,” he told Healthline.

There are no specific medications to treat West Nile virus disease or vaccines that can prevent it.

People of any age can develop severe illness if they contract West Nile virus. But those 60 years of age or older are at greater risk for more serious disease.

Other people with a higher risk for severe illness from West Nile include those with certain health conditions, including:

  • cancer
  • diabetes
  • high blood pressure

Immunocompromised people and those with other medical conditions may also face higher risks.

Eastern equine encephalitis, or EEE, is a rare but potentially deadly disease caused by a virus passed onto people through the bite of an infected mosquito.

EEE passes between mosquitoes and birds found in freshwater hardwood swamps. Another mosquito species is needed to pass the virus from infected birds to people or horses.

Most people who contract the virus don’t develop symptoms. Those who do become infected may develop mild symptoms such as:

  • fever
  • chills
  • body aches
  • joint pain

Some people may develop more serious inflammation of the membranes surrounding the brain and spinal cord. About one-third of people who develop severe eastern equine encephalitis die from their illness.

“In worse cases, the virus infects the tissue of the brain, and that’s when we call it encephalitis,” said Siegel. “That is more serious and is much more likely to lead to death or long-term neurological deficits in patients who survive.”

Sullivan said both very young children and older adults are at higher risk of severe illness from eastern equine encephalitis. In contrast, West Nile virus tends to affect older adults more than young children, he said.

Most cases of eastern equine encephalitis occur in eastern or Gulf Coast states. In 2025, no cases have yet been reported to the CDC, and only 19 cases were reported in 2024.

There is no vaccine treatment for eastern equine encephalitis. People with severe symptoms will be given medications and other therapies to manage their symptoms.

The World Health Organization (WHO) estimates that around 263 million malaria cases occurred globally in 2023, with around 597,000 deaths resulting from the disease.

Malaria is caused by a parasite that infects a certain type of mosquito. Cases typically occur in tropical parts of the world, particularly in Africa.

Malaria was once common in parts of the United States but was declared eliminated during the mid-1950s. However, around 600 malaria cases were imported into the United States in 2020 by people traveling to other parts of the world.

In 2023, several locally acquired malaria cases occurred in Florida and Texas for the first time since 2003.

Symptoms of malaria, which can include flu-like illness and headache, range from mild illness to severe disease.

Prescription drugs are available to treat and cure malaria. Antimalarial medications are available as a preventive option for those traveling to regions where malaria is endemic. A malaria vaccine is also available in parts of the world where malaria regularly occurs, such as in parts of Africa.

According to the CDC, up to 400 million people worldwide are infected with the dengue virus each year.

Not everyone who contracts dengue develops symptoms, which may include:

  • aches
  • eye pain
  • muscle or joint pain
  • nausea
  • vomiting
  • rash

Dengue is most commonly found in tropical and subtropical areas of the world, but cases do occur in the United States.

So far this year, the CDC has confirmed 2,096 dengue cases in 39 U.S. jurisdictions.

However, most cases reported in the continental United States occurred in travelers who contracted the virus in other areas.

There is no specific treatment for dengue, but people may be given medication to relieve pain.

In the United States, a dengue vaccine is available for use in children ages 9 through 16 who live in an area where dengue is common and have laboratory confirmation of a previous dengue infection.