The Hidden Dangers of Mosquito Season

West Nile virus is carried by mosquitoes and can pose health risks

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

Ah, summer ... picnics, barbecues, swimming, vacations and West Nile virus. Yes, unfortunately, West Nile can go along with all those fun things.

Don’t let West Nile virus be your summer spoiler. Get educated and protect yourself and your loved ones.

A Bit of History

West Nile virus is an insect-carried virus most commonly spread by infected mosquitoes. West Nile virus can cause fever, inflammation of the brain (encephalitis), or inflammation of the lining of the brain and spinal cord (meningitis), according to the Centers for Disease Control and Prevention (CDC).

Most patients infected with the virus either don't experience any signs or symptoms or experience only minor ones. However, some patients infected with West Nile can develop life-threatening illnesses.

According to a 2003 historical review in The Oschner Journal, the first known case of West Nile virus was found in Uganda in 1937. Outbreaks in the Mediterranean occurred periodically for about 60 years.

In 1996, a large West Nile outbreak occurred in an urban area of Romania. The Romanian outbreak was the first in which most patients showed severe illness and neurological symptoms, such as meningitis.

By 1999, the virus had been found in the US. According to the CDC, West Nile virus has been found in all US states except Alaska, Hawaii and Maine. New Hampshire and Vermont have only reported infections in animals.

“The worst epidemic we’ve ever had [of West Nile virus in the US] was in 2012," said David Winter, MD, chief clinical officer, president and chairman of the board of Baylor Health Care System's HealthTexas Provider Network, in an interview with dailyRx News. "286 people in Texas died with that."

It’s the Mosquitoes

West Nile virus is spread by infected mosquitoes. Mosquitoes get the virus by feeding on infected birds.

Those who live in an area where West Nile virus is present can become infected if they are bitten by an infected mosquito.

In very rare cases, West Nile virus has been spread between humans through procedures like blood transfusions or organ transplants, according to the CDC. Infected mothers can also spread the virus to babies during pregnancy, delivery or breastfeeding.

You May Not Know It

Once a person is bitten by an infected mosquito, the signs of West Nile usually appear within two to 14 days. However, the majority of those who do develop an infection have no symptoms.

According to Dr. Winter, about 20 percent will develop a fever, headache, extreme fatigue or muscle aches. Other symptoms may include vomiting, diarrhea or rash.

When West Nile Is Bad News

A very small number of people can develop serious neurological problems, according to Dr. Winter.

“Less than 1 percent get those terrible neurological symptoms — encephalitis (infection of the brain) or meningitis (infection of the lining of the brain)," Dr. Winter said. "You can even get a polio-like syndrome where you get paralysis."

In severe West Nile virus infections, symptoms may include severe headache, stiff neck, high fever, confusion, coma, seizures or paralysis. According to the CDC, of those patients who develop the neurological form of the disease, about 10 percent will die.

According to the CDC, recovery may take weeks to months, and some neurological effects may be permanent. Those who have chronic medical conditions, such as cancer or diabetes, are also more likely to develop the severe form of West Nile.

Diagnosis and Treatment

Doctors may diagnose West Nile based on a patient’s symptoms, or with blood or spinal fluid tests. Patients may receive medicines to reduce fever and supportive care to help the body fight the infection, such as intravenous fluid.

No specific medication or vaccine currently exists for West Nile virus.


Prevention is the best way to avoid West Nile virus, according to Dr. Winter.

“The main treatment is to try to prevent contact with mosquitoes,” Dr. Winter said.

The time of the year when infection risk is highest is June to September, when mosquitoes are most active. Many factors can affect outbreaks, such as climate, the number of infected birds and the size of a mosquito population.

Dr. Winter recommends using a mosquito repellent when outside and wearing long sleeves and pants during the periods when mosquitoes are most active (shortly after dawn and at dusk). The screens on windows and doors should also be in good repair to keep mosquitoes out of the home.

You can decrease possible mosquito breeding areas by getting rid of standing water in buckets, puddles and birdbaths. If you have a birdbath or pet water dishes outside, empty and refill them daily.

If you think you or a family member has West Nile virus, contact your doctor immediately.

Review Date: 
June 10, 2015
Last Updated:
June 18, 2015