Mosquito-Borne Disease Prevention Tips for Older Adults

Written by:

Jason Kolkey

8 min read

Key Takeaways

Certain mosquitoes can spread diseases, like the West Nile virus and eastern equine encephalitis, to humans.
Take precautions to prevent mosquito bites, such as using insect repellent and wearing long sleeves outside.
Medicare coverage can help you access care for mosquito-borne diseases.

During the summer of 2024, many people in the U.S. realized that the mosquito buzzing in your ear can be far more than just an annoyance. The diseases carried by the blood-drinking insects attracted wide attention in August, when a New Hampshire resident died from eastern equine encephalitis and Dr. Anthony Fauci, formerly the nation’s top infectious disease expert, was hospitalized with West Nile virus.

There’s a variety of illnesses spread by mosquitoes, and some are especially problematic for older adults. By learning about how these little insects can pose big health concerns, you’ll be better prepared to take precautions and, if necessary, seek treatment.

Mosquito-borne Diseases in the U.S.

Not every mosquito is dangerous to humans. According to the Centers for Disease Control and Prevention (CDC), out of the more than 200 types of mosquitoes found in the U.S., around a dozen are capable of spreading germs to people.

When mosquitoes feed on a person or animal, they may take blood that contains a virus or bacteria. Some of those germs are able to grow or reproduce in the insect’s body and eventually move into its salivary glands. Then, the mosquito spreads the infection or virus when it bites another person or animal.

The illnesses transmitted by mosquitoes in the U.S. include:

West Nile virus
Eastern equine encephalitis
Cache Valley virus
Jamestown Canyon virus
La Crosse encephalitis
St. Louis encephalitis

In addition, there have been outbreaks of dengue, chikungunya, and Zika in U.S. states and territories. You are at greatest risk of catching an illness from a mosquito in the summer or early fall, when the insect population is at its peak.

Preventing Mosquito Bites

For several of the mosquito-borne illnesses found in the U.S., there’s no vaccine available. However, you can lower your chances of getting sick by taking precautions to minimize bug bites:

Use an EPA-registered insect repellent with ingredients like DEET or picaridin.
Wear pants and a long-sleeved shirt.
Treat clothes with the insecticide permethrin.
Remove any potential mosquito habitats such as standing water in buckets, trash cans, tree holes, gutters, or fountains from around your home.
Repair any holes in the screens on windows and doors.

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What Is West Nile Virus?

West Nile virus is the disease most commonly spread from mosquitoes to humans in the continental U.S.

Before this virus reaches a person, it passes between birds and mosquitos: An insect may catch it by feeding on one infected bird and then pass it to a different bird. Certain species of birds might also catch West Nile when they eat either an infected mosquito or another bird that has the virus.

A human can catch the disease from a mosquito bite, but not from a bird (the CDC nonetheless advises always wearing gloves if you handle a dead bird due to the risk of avian flu). Once a person has the virus, they can’t infect another mosquito, but in rare cases the virus can be passed between people through a blood transfusion, organ transplant, pregnancy, or breastfeeding.

What Are the Symptoms of West Nile Virus?

For most people who catch West Nile virus, there are no apparent signs of the infection. However, about one in five people experience symptoms like:

Fever
Body aches
Headache
Rash
Swollen lymph glands

Especially for older adults, there’s a possibility for West Nile virus to cause more serious illnesses such as encephalitis (Inflammation of the brain) or meningitis (inflammation of the membranes that cover the brain and spinal cord). Symptoms may include:

Headache
High fever
Neck stiffness
Extreme tiredness
Disorientation
Coma
Tremors or convulsions
Muscle weakness or paralysis

There’s no vaccine or specific treatment against West Nile virus, though most people who recover gain immunity against catching the disease again. Those who have meningitis symptoms might need rehydration and pain medication to manage their headaches. Patients who develop signs of encephalitis may be admitted to a hospital in case of seizures or breathing problems.

What Is Eastern Equine Encephalitis?

The virus that causes eastern equine encephalitis (EEE) is another that travels between mosquitoes and birds, usually in swamp areas. It’s called “equine” because it can also infect horses and a variety of other animals. People and animals who catch EEE do not transmit it to others.

Human cases are rare in the U.S., mostly appearing in the eastern states and along the Gulf of Mexico. However, when people do catch EEE, it’s extremely dangerous. The symptoms include:

Fever
Headache
Drowsiness
Vomiting
Diarrhea
Seizures
Behavioral changes

About 30% of people with this form of encephalitis die, often within 10 days. Around half of those who survive have long-term neurological effects that may require long-term care and shorten their lives, such as intellectual disabilities, seizures, paralysis, personality disorders, and cranial nerve dysfunction.

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U.S. Cases of Malaria

Malaria is caused by a parasite carried in the Anopheles mosquito. It’s a major global health problem that mainly affects residents of tropical countries: The World Health Organization reported that more than 600.000 people die annually of malaria.

The most common malaria symptoms are fever, headache, and chills. People with severe cases may experience:

Extreme fatigue
Impaired consciousness
Convulsions
Difficulty breathing
Dark or bloody urine
Yellowing eyes and skin
Abnormal bleeding

Malaria has been rare in the U.S. since the 1950s. There are about 2,000 cases reported a year, but most are in people who traveled outside the country; only a small fraction are transmitted locally. If you do need to travel to an area where malaria is common, consult with your doctor about medications you can take before and during your trip to lower the chances of infection.

Other Mosquito-borne Diseases

Mosquitoes in the U.S. sometimes carry a variety of other diseases with the potential to damage your health. These include rare viruses that can trigger serious inflammation, so it’s vital to seek medical help if you feel symptoms.

What Is Cache Valley Virus?

Cache Valley virus passes between mosquitoes and various types of animals, like cows, deer, horses, and sheep. It can cause encephalitis or meningitis with symptoms like:

Neck stiffness
Loss of coordination
Confusion
Speech problems
Seizures

Cache Valley virus is rare in the U.S., but a few cases have been reported in the late spring and early fall.

What Is Jamestown Canyon Virus?

Jamestown Canyon virus circulates between mosquitoes and other animals like deer. Cases have been reported across the U.S., especially in the upper Midwest. The primary symptoms are fever, headache, and fatigue, but like other mosquito-borne viruses, it can cause encephalitis.

What Is La Crosse Encephalitis?

The La Crosse virus is another mosquito-borne illness with the potential to cause encephalitis, particularly for children under 16 years old. Usually there are no symptoms, but infected people may experience fever, headache, nausea, vomiting, and fatigue.

The La Crosse virus is carried by mosquitoes that breed in tree holes and by small mammals such as squirrels. Cases have been reported in the upper Midwest, mid-Atlantic, and Southeast regions of the U.S.

What Is St. Louis Encephalitis?

The St. Louis virus, which appears in both North and South America, can be deadly for up to 15% of people diagnosed. Like West Nile virus, this illness circulates between humans and birds and usually causes no symptoms. However, there are rare cases of encephalitis and meningitis, and the effects tend to be especially bad for older adults.

Symptoms usually begin between four and 14 days after the bite, including fever, headache, nausea, dizziness, and muscle weakness. Over the following several days, the symptoms usually worsen, but then many people recover. Those who develop infections in their central nervous system can experience confusion and disorientation, a stiff neck, dizziness, tremors, and a loss of control over their movements. In the most severe cases, they may fall into a coma.

While people with mild cases can get better with some rest, fluids, and pain medication, those with severe disease need to be hospitalized.

Medicare Coverage and Mosquito-Borne Illness

Most U.S. citizens or permanent residents who are over 65 — as well as those with certain disabilities — rely on Medicare for their health insurance. Either the federally administered Original Medicare program (also called Medicare Parts A and B) or a Medicare Advantage plan from a private insurance carrier can cover outpatient treatment and inpatient hospital stays for illnesses caused by a mosquito bite.

If you’re prescribed medications to take at home, you’ll need coverage from a Medicare Part D prescription drug plan. People on Original Medicare can choose a standalone Part D plan from a private insurance carrier. Most Medicare Advantage plans include Part D prescription drug coverage.

Certain Medicare Advantage plans may provide additional benefits that can help to prevent mosquito-borne illness. For example, some feature a credit to pay for over-the-counter items like insect repellent.

Protecting yourself from mosquito bites could prevent serious health consequences. Take precautions when you’re enjoying the outdoors, and make sure you have the right insurance coverage in case of an unexpected illness.