West Nile

west nile mosquito

West Nile virus is one of the more common mosquito-borne illnesses in the United States. Originally discovered in humans in the West Nile region of Uganda in 1937, the disease is now commonly found in Africa, Europe, the Middle East, North America and West Asia.

According to the Centers for Disease Control and Prevention (CDC), cases of the disease in the United States occur during mosquito season, which runs from spring to fall (and in some parts of the U.S, year-round), and cases have been reported in all of the continental United States. In 2017, there were 2,002 cases reported to the CDC.

Learn more about the causes and symptoms of West Nile virus and how you can help prevent exposure.

What is West Nile Virus?

West Nile virus is a viral infection spread to humans through the bite of infected mosquitoes. These mosquitoes contract the disease from infected birds. They then spread West Nile to humans and animals.

The most common vectors of West Nile in the United States are mosquitoes of the Culex species. These include Culex pipiens, or the house mosquito, and Culex quinquefasciatus, or the southern mosquito./p>

Culex pipiens are common in the northern United States. They are pale brown with white stripes and are found in areas of standing water.

Culex quinquefasciatus are typically found in tropical and sub-tropical regions. In the United States, they are common in the South, particularly Florida. They are similar in appearance to Culex pipiens.

Both these species of mosquitoes are nighttime feeders.

Related: Different Types of Mosquitoes

West Nile Virus Symptoms

While the West Nile virus can lead to serious infection, the Mayo Clinic notes that most people infected with the disease do not experience any symptoms. The disease has an incubation period ranging from 2 to 14 days.

Roughly 20 percent of people infected develop a mild infection known as West Nile Fever. Symptoms of West Nile Fever include:

  • Fever
  • Headache
  • Body aches
  • Vomiting
  • Diarrhea
  • Fatigue
  • Skin rash

The CDC states that most patients with these symptoms recover completely, although fatigue and weakness can last for weeks or months.

In less than 1 percent of cases, West Nile virus can lead to a serious neurological infection, including brain swelling. Symptoms include:

  • High fever
  • Severe headache
  • Stiff neck
  • Disorientation or confusion
  • Stupor or coma
  • Tremors or muscle jerking
  • Seizures
  • Partial paralysis or muscle weakness

While mild symptoms of West Nile virus usually resolve on their own, brain swelling can last for weeks or months, and muscle weakness may be permanent. The Mayo Clinic recommends that anyone experiencing severe West Nile virus symptoms seek medical attention right away.


According to the CDC, there is no vaccine or specific antiviral medications for West Nile virus. However, over-the-counter pain relievers can be used to reduce fever and alleviate symptoms. Severe West Nile infections may require hospitalization and additional treatments such as IV fluids and pain medication.

Mosquito Bite Prevention

You can try to avoid being bitten by mosquitoes by helping prevent their activity in the first place. Primarily, you should eliminate standing water around your house, as mosquitoes use this for breeding. Tips include:

  • Unclogging gutters to prevent debris and water from accumulating
  • Emptying unused swimming pools
  • Changing water in bird baths and pet bowls regularly
  • Removing containers or old tires that may trap water

Related: Four Tips to Help You Prepare for Mosquito Season

You can also help reduce your chances of being bitten by:

    Avoiding outdoor activities during dawn and dusk, when mosquitoes are most active
    • Wearing long sleeves and pants
    • Using a mosquito repellent recommended by the CDC