West Nile virus is the most common mosquito-borne virus in the continental United States. West Nile virus can cause anything from a mild asymptomatic infection to a severe, potentially fatal infection.

West Nile virus is the most common virus that spreads through mosquito bites in the continental United States, according to the Centers for Disease Control and Prevention (CDC).

Mosquitoes come in contact with the virus by feeding on birds that have the virus. Humans get the virus when a mosquito bites them and feeds on them.

Only about 1 in 5 people who get West Nile virus develop any symptoms, the CDC says. About 1 in 150 people with the virus develop a serious, potentially life threatening infection.

West Nile virus typically spreads during the summer and into the fall. A person can reduce their risk of exposure by using insect repellents and taking steps to reduce the mosquito population around their home. Steps to reduce mosquitoes can include removing sources of standing water and removing leaves and other debris from the yard.

In this article, we explore the symptoms of West Nile virus, its diagnosis, its treatments, and the outlook for a person with a West Nile virus infection.

Around 8 in 10 people who contract West Nile virus show no symptoms, according to the CDC.

About 1 in 5 will develop mild symptoms that can include:

Though most people recover completely, some may develop fatigue or weakness that can last for weeks to months.

About 1 in 150 people will develop a much more serious infection from West Nile virus, the CDC reports. Symptoms of a more severe infection can include:

  • severe headache
  • muscle weakness
  • high fever
  • neck stiffness
  • tremors
  • stupor
  • numbness
  • disorientation
  • coma
  • convulsions
  • vision loss
  • paralysis

Though anyone can develop a serious infection, people who are over age 60, are living with certain medical conditions, or are immunocompromised have a higher risk of experiencing severe symptoms of West Nile virus.

To diagnose West Nile virus, a doctor will typically need to order tests to check for the virus.

Often, a doctor will order a blood test. The sample will go to a lab, where lab technicians scan for West Nile virus-specific IgM antibodies. The antibodies will typically show up within 3 to 8 days, the CDC says, but they can last for about 30 to 90 days in the body.

If a person has symptoms and gets a test within 8 days, a doctor may not be able to rule out West Nile virus. They may need to repeat the test in a few days.

Because a person cannot obtain a home test without a doctor visit, they should follow up with their doctor following any positive test results if they think they may need to re-test.

Treatment will vary depending on the severity of the infection.

For mild cases, over-the-counter (OTC) pain medications may be enough to manage pain and help reduce fever. A person may find that acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) help with pain and fever reduction.

However, a person may wish to speak with their doctor before taking OTC medications, particularly if they have any underlying health conditions or are taking other medications.

For more severe infections, a person may require hospitalization. Doctors will likely monitor the person’s condition, as well as provide nursing care, intravenous (IV) fluids, and more powerful pain relievers. They can also help prevent death due to the virus.

Currently, there is no human vaccine for West Nile virus. Prevention should focus on using insect repellents, avoiding mosquito-heavy areas, and taking steps to reduce breeding grounds around the home by removing standing water and natural debris or by installing mosquito traps or zappers.

Most people who develop a mild infection will completely recover. Some may develop fatigue and weakness that can last for several weeks to months.

Once they have the virus, a person will likely develop immunity to West Nile virus. In other words, they will not get sick again if they come in contact with the virus a second time.

People with severe infections may need hospitalization and more intense care. Care in the hospital may include the administration of more intense pain medication and IV fluids, neurologic and respiratory support, and general nursing care.

West Nile virus is a mosquito-spread virus present in the entire continental United States. It may cause no symptoms, mild symptoms, or severe symptoms that require hospitalization.

Symptoms can include fever, body aches, and headache. More severe symptoms can include vision loss, paralysis, and coma.

Treatment is nonspecific and often involves pain and fever reducers. In the hospital, doctors will likely administer fluids, conduct intense monitoring, and manage symptoms.

In most cases, a person will fully recover. Some may go on to develop long lasting fatigue or weakness following recovery from the fever and other symptoms.