How To Protect Yourself From Mosquito-Borne Illnesses

Mosquitoes, ticks and fleas may be small, but they can spread diseases that cause serious health problems.

As rain continues to fall, temperatures rise and insects move into new areas, health experts are seeing more insect-borne illnesses across the United States.

From West Nile virus and Zika to diseases spread by ticks and fleas, understanding how these illnesses spread — and how to protect yourself — can help you stay healthy year-round.

Climate Change Makes Insect-Borne Illness More Common

Dr. Jason Bowling is the chief epidemiologist at University Health and a former president of the Texas Infectious Disease Society. He says warmer temperatures are helping disease-carrying insects, known as vectors, survive and spread. These insects pick up germs from people or animals and pass them on through bites.

“As the climate continues to change, we may see these diseases spread to new areas,” Dr. Bowling said. “The vectors start to move from where they were before, because the (warming) climate makes it more favorable for them.”

Mosquito Season Is Getting Longer

Fleas and ticks can spread disease, but Dr. Bowling says mosquitoes are the “number one bad actor.” If it feels like mosquitoes are around for more months each year, you're not imagining it.

A non-profit that tracks the effects of warmer weather reports that from 1979 to 2022, about 71% of U.S. locations saw the average mosquito season last longer — by an average of 16 days.

Diseases Spread by Mosquitoes

West Nile

West Nile virus is the most common mosquito-borne disease in the U.S.

Many people who get West Nile virus do not feel sick. About 20% will recover quickly after developing mild symptoms like a fever, headache, body aches or a skin rash. In some cases, the virus can affect the brain and spinal cord. This can cause muscle weakness, paralysis or death. In 2003, a West Nile outbreak caused more than 40 deaths in Texas.

What Are the Odds of Getting West Nile Virus?

“West Nile virus is found every year in Bexar County and across Texas,” said Dr. Bowling. “In fact, mosquitoes in our area have already tested positive for the virus this year.”

Dr. Bowling explained that the chances of getting West Nile virus are usually low. However, your risk is higher if you are exposed to more mosquito bites. “People who are older or have weakened immune systems are also more likely to get very sick if they are infected,” Dr. Bowling said.

Malaria

Malaria is a serious disease caused by a parasite that spreads through mosquito bites. It can make people feel very sick with flu-like symptoms and, in some cases can be deadly.

In the United States, most people who get malaria were infected while traveling or living in another country where the disease is common.

What Are the Odds of Getting Malaria?

Dr. Bowling said, “your chances of getting malaria depend on where you travel.”

Some countries have a higher risk because malaria is more common there.

If you plan to travel to one of these areas, like South America, it is important to talk to a healthcare provider first. They may recommend medicine to help prevent malaria before, during, and after your trip.

Zika

Zika is a virus that usually causes mild flu-like symptoms. However, it can be very dangerous for someone who is pregnant because it can cause serious brain and birth defects in an unborn baby.

Zika spreads mainly through the bite of an infected mosquito. It can also be passed to a partner during sex.

Other mosquito-borne diseases tracked by the Texas Department of State Health Services include chikungunya, dengue, St. Louis encephalitis and western equine encephalitis.

What Are the Odds of Getting Zika?

“The risk of getting Zika in the U.S. is very low,” said Dr. Bowling. “There have been no confirmed cases of Zika virus infection in the U.S. since 2019.”

Illnesses Spread by Fleas and Ticks

Many diseases spread through tick bites, including Lyme disease and Rocky Mountain spotted fever. These illnesses are rare in South Texas.

Here, fleas are a bigger concern because they can spread murine typhus.

Rodents, opossums and domestic cats often carry fleas that can spread to people. A flea bite can lead to a bacterial infection. In some cases, this infection may require hospitalization. If not treated quickly, it can cause serious illness, including life-threatening sepsis.

Diagnosing and Treating Diseases Transmitted by Insects

Many insect-borne illnesses have similar symptoms. They often feel like the flu and may include:

• Fever
• Headaches
• Muscle aches
• Nausea
• Rash

Dr. Bowling says patients need to see their primary care provider to get the right diagnosis and treatment.

“Many of these generally don't respond to standard antibiotics,” Dr. Bowling said. “For example, if you get penicillin, it's not going to treat murine typhus. Malaria requires anti-malaria medication. You need a provider to make the diagnosis so you can get the right treatment.”

Treating Minor Mosquito Bites

A typical mosquito bite usually causes redness, itching and mild swelling.

You can help reduce itching by:

• Applying an anti-itch cream or hydrocortisone cream
• Using a cold compress
• Taking an antihistamine, if recommended by your healthcare provider
• Avoiding scratching, which can increase irritation

Most mosquito bites improve on their own within a few days. Dr. Bowling recommends seeing a doctor if a bite does not improve or if you develop:

• Fever
• Severe swelling
• Signs of infection
• A spreading rash

“If you get a mosquito bite or flea bite, that doesn't mean you are going to get these things. But, if you start to develop symptoms, after you have a bunch of mosquito or flea bites, get it checked out,” Dr. Bowling said.

Prevention is Key

Avoiding insect bites is the best way to prevent insect-borne illnesses. 

The Centers for Disease Control and Prevention recommends these steps to protect against mosquito bites:

• Use insect repellent that works
• Wear long sleeves and long pants when possible
• Empty standing water in outdoor containers where mosquitoes can breed
• Keep mosquitoes outside by closing doors and windows, using screens and running air conditioning

How To Choose the Best Insect Repellent

Not all insect repellents work the same. Dr. Bowling recommends using EPA-registered insect repellents with proven active ingredients, such as:

• DEET
• Picaridin
• Oil of lemon eucalyptus

“These ingredients are shown to provide effective protection,” said Dr. Bowling. “Some products sold in stores may not work well, so it’s important to check the label.”

Preventing Flea-Borne Illness

To help prevent murine typhus and other flea-related illnesses:

• Use flea prevention products for pets
• Remove food sources and nesting areas near your home that attract wild animals
• Do not feed or shelter wild or stray animals

Dr. Bowling says there’s no reason to panic if you are bitten by mosquitoes or fleas. Just be aware of any symptoms.

Infectious Disease Care at University Health

Find care for infectious diseases like malaria, Zika, West Nile and more at University Health in San Antonio.