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 with the highest risk of becoming severely ill include people 55 years of age and older, with certain medical conditions, and who have weakened immune systems.
West Nile season in NYC occurs between May and October.
Learn about upcoming mosquito control events.
Transmission
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.
Risk Groups
People 55 years and older are at the greatest risk of severe illness from contracting West Nile. Medical conditions associated with increased risk of severe illness include chronic kidney disease, diabetes, cancer (especially blood cancers), and hypertension. Conditions and treatments that weaken the immune system include organ transplantation, cancer, and cancer and autoimmune disease medications including B cell therapies (such as rituximab and ocrelizumab).
Prevention
Mosquitoes that carry West Nile bite around dusk and dawn. Be sure to protect yourself from mosquitoes by using an EPA-approved 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. Clean and chlorinate swimming pools, outdoor saunas, and hot tubs. Keep them empty or covered when not in use.
Wear longs pants, long sleeve shirts, and socks, in addition to using repellent, especially during dawn and dusk. People with severely compromised immune systems should avoid going outdoors during dusk and dawn when mosquitoes that carry West Nile virus are active and bite.
West Nile is present throughout the U.S. and in other parts of the world. When you travel, check with the local health department or visit the CDC Travelers' Health Page to see if West Nile or any other arboviruses are present.
Symptoms
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 myelitis, 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 55 are at greater risk, with certain medical conditions, and who have weakened immune systems are 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.
Testing
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.
Treatment
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 a pregnant person to their fetus is low. Most infants born to people infected with West Nile while pregnant do not have evidence of infection or disease. However, there have been a small number of cases of West Nile in newborns.
West Nile has been detected in breast milk of people with West Nile infection. However, there are very few reports of transmission through breastfeeding and none of the infants developed illness. 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.
Serious illness from West Nile virus is more common in adults than in children. Most children who get the virus will only have a mild illness. It’s still possible for children to get very sick, but this is very rare. Children with weakened immune systems or who already have a serious illness are more likely to be very sick.
Blood and Organ Donation
In rare cases, people have become infected with West Nile through a blood donation or organ transplant. All donated blood products and some organ donations are tested for West Nile virus to reduce this risk of transmission. 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 start having symptoms.
Pets
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.