West Nile Virus

West Nile virus is spread through the bite of an infected mosquito. West Nile virus can infect humans, birds, horses and other mammals.

Most people infected with West Nile either have no symptoms or experience a mild to moderate illness. People who are older than 60 have the highest risk of becoming severely ill. There is increasing evidence that people with weakened immune systems are also at higher risk.

West Nile season in NYC occurs between May and October.

Learn about upcoming mosquito control events.


West Nile cannot be spread person-to-person through casual contact. In rare cases, the virus has been spread through transfusions of infected blood or transplantations of infected organs.

It is not possible to become infected simply by handling dead birds. If you are disposing of dead birds or other small animals, use gloves and put the carcass in double plastic bags before placing them in a garbage can.


Mosquitoes that carry West Nile bite around dusk and dawn. Be sure to protect yourself from mosquitoes by using insect repellent. You can also take steps to reduce mosquitoes around your home.

Standing water may allow mosquitoes to breed. From April through October, you can report standing water in NYC.

West Nile is present throughout the U.S. and in other parts of the world. When you travel, check with the local health department to see if West Nile — or any other arboviruses — are present.


Most people infected with West Nile do not develop any symptoms. For those who do become ill, symptoms usually appear between three and 15 days after you are bitten by an infected mosquito.

Mild to Moderate Illness

Some people experience a mild to moderate illness. Symptoms include:

  • Fever
  • Headache
  • Tiredness/weakness
  • Body aches and joint pain
  • Vomiting
  • Diarrhea
  • Rash

Severe Illness

In rare cases, West Nile can cause a severe illness that can affect the brain and spinal cord. This can lead to encephalitis, meningitis or acute flaccid paralysis, which is a polio-like syndrome where muscles become weak or paralyzed.

Symptoms of this illness include:

  • High fever
  • Headache
  • Neck stiffness
  • Muscle weakness
  • Tremors or shakes
  • Confusion
  • Numbness and paralysis
  • Coma

Severe illness can occur at any age, though people older than 60 are at greater risk. People with certain medical conditions, such as cancer, diabetes, high blood pressure, kidney disease, and people who have received organ transplants, are also at greater risk.

Recovery from severe illness might take several weeks or months. Some patients will have long-term symptoms that affect their lives daily.


Contact your doctor if you develop West Nile symptoms. Your doctor can conduct a blood test to determine if you are infected with West Nile.


There is no treatment for West Nile. Most people who become infected will get better on their own.

People with mild or moderate symptoms should recover completely. Some symptoms may last for weeks. Generic medicine, like acetaminophen, can help relieve symptoms. Speak with your health care provider about what’s best for you.

Pregnant Women and Children

The risk of transmission from mother to fetus is low. There have only been a few reported cases of West Nile in newborns.

In one case, an infant likely became infected through breast milk. The health benefits of breastfeeding have been well established and there are no recommendations to stop breastfeeding because of West Nile. Repellents registered with the EPA are safe for pregnant and breastfeeding women.

Children who attend school, camp or go on trips outdoors during the daytime are at low risk for mosquito bites. Ticks and some types of mosquitoes can still be active during the day. If your child will be around areas where mosquitoes are active, take precautions to protect them from mosquito bites.

Blood and Organ Donation

In rare cases, people have become infected with West Nile through a blood donation or organ transplant. Routine testing of donated blood products reduces this risk of transmission and is mandatory in NYC. If you have symptoms of West Nile virus or other concerns after a blood transfusion or organ transplant, talk to your health care provider.

People infected with West Nile virus should not donate blood for 120 days after they started having symptoms.


Pets can get West Nile. Most will not get sick and cannot spread the virus to people. Repellents recommended for humans are not approved for pet use. Speak with your veterinarian about appropriate products to use on your pets to prevent mosquitoes and other insects.

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