Understanding West Nile Virus, WNV Symptoms & WNV Treatment
What is West Nile Virus?
West Nile Virus (WNV) is the most common mosquito-borne virus in the United States that affects humans, primarily when transmitted through mosquito bites. Mosquitos get the virus from infected birds. West Nile Virus can cause serious illness and even death in humans.
The virus is named for the West Nile district in Uganda where it was first identified in 1937. West Nile Virus is an arbovirus, meaning it is transmitted to humans through anthropods (animals without a backbone, including the mosquito).
Effects of West Nile Virus
Many times, people with WNV won’t experience any symptoms. If they do, the symptoms are usually minor, such as a slight fever or a mild headache.
But once the virus is in the bloodstream, it can enter the central nervous system (CNS). If the virus enters the CNS, this neuroinvasive form of WNV can cross the blood-brain barrier, which is a border of cells preventing disease-causing pathogens from entering the brain.
This can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the tissue that surrounds the brain and the spinal cord). Roughly 1 in 10 people with neuroinvasive virus die from the disease.
WNV facts
- There is no vaccine or cure for WNV.
- Most people’s immune system fights off West Nile, with recovery in 1-3 weeks.
- The virus does not spread person-to-person.
- Incubation period from transmission to symptoms is generally 3 to 14 days.
- Rarely, WNV can be transmitted through organ transplants, blood transfusions, during pregnancy from mother to fetus, and in breastfeeding.
- Severe cases of WNV can have long-term effects such as hearing loss, memory loss, gait disorders, depression and reflex problems.
ID Care has more than 50 highly skilled infectious disease physicians, a broad medical support staff of nurse practitioners and physician assistants, and a commitment to patient-centric, empathetic care. Make us your source for excellent infectious disease care.
West Nile Virus in New Jersey & the U.S.
Although West Nile Virus is commonly found in Africa, Europe, the Middle East and western Asia, it has also been seen throughout the United States. The virus first appeared in the U.S. in 1999.
To combat WNV, the New Jersey Department of Health (NJDOH) advised residents in July of 2025 to take steps to reduce pools of standing water that can support mosquito larva. In the summer of 2025, the state detected 143 mosquito pools that tested positive for WNV.
In 2024, 41 cases of WNV were reported in the state, resulting in three deaths. At the time of this webpage’s publication, NJDOH says no New Jersey cases of WNV have been recorded in 2025.
The Centers for Disease Control and Prevention (CDC) reports 60,992 total cases and 3,134 deaths in the U.S. from 1999-2024. The total West Nile cases in the U.S. for 2025 thus far total 98. Of those cases, 53 entered the central nervous system.
Anyone can get West Nile, which is most prevalent in summer and early fall months when more mosquitos are present. People over 60 years of age with weak immune systems are most at risk for severe illness.
West Nile Virus questions & answers:
What is West Nile Virus?
West Nile Virus is the most common mosquito-borne virus in the U.S., usually causing no symptoms or flu-like symptoms that clear in 1-3 weeks.
Is West Nile Virus deadly?
Yes. WNV can enter the central nervous system and become deadly in 1 out of 10 such cases, which equates to about 1 death per 1,500 of all WNV cases.
How is West Nile Virus transmitted?
Humans get the virus when bitten by a mosquito carrying the virus, which it acquires from feeding on infected birds. Rarely, it can be transmitted in organ transplants, blood infusions & in pregnancy.
Is West Nile Virus curable?
No, there are currently no vaccines or treatments to cure WNV. Our doctors can alleviate symptoms and treat aspects of WNV in the central nervous system such as encephalitis and meningitis.
Who is at risk of becoming ill from West Nile Virus?
Those at risk of severe effects of the virus include:
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- People over age 60.
- Organ transplant or blood transfusion recipients.
- Patients with cancer, diabetes, high blood pressure and kidney disease.
West Nile Virus symptoms, including West Nile fever
According to the World Health Organization, approximately 80% of people who are infected with WNV will not show any symptoms. Only about 1% of those with WNV experience severe symptoms.
Those who do have symptoms may experience flu-like symptoms, which are often referred to as West Nile fever.
West Nile fever symptoms
Neuroinvasive WNV symptoms (West Nile encephalitis, meningitis or poliomyelitis)
- High fever.
- Muscle weakness.
- Intense headaches.
- Tremors and convulsions.
- Coma.
- Paralysis.
Diagnosing WNV
Confirming whether a patient has WNV at ID Care requires a variety of laboratory tests, the most common being a blood test. These tests look for antibodies or other signs of the virus. Typically, we only do these tests in patients who are very ill.
In some cases we may recommend that the patient has a spinal tap or radiological imaging at one of our affiliated hospitals to confirm the presence of WNV or another related illness, such as meningitis or encephalitis.
West Nile Virus treatment
Unfortunately, no specific vaccines or treatments for WNV exist today. But our team of ID Care researchers is working with government agencies to help develop one in the future.
We recommend treating the flu-like symptoms with over-the-counter medications. For fever and body aches, these include acetaminophen (Tylenol), ibuprofen (Advil) and naproxen (Aleve). Medications for cough and colds can also help.
Those with neuroinvasive West Nile can require hospitalization. Our providers and physicians can provide treatments in the hospital such as respiratory support, intravenous fluids and antibiotics to prevent secondary infections (antibiotics are not effective against WNV itself).
Additional hospital treatments for symptoms and brain swelling can involve anti-seizure medications, corticosteroids and other measures.
WNV prevention
Prevention of WNV by the individual comes down to preventing being bitten by mosquitos. Follow NJDOH’s advice to eliminate pools of standing water at your home that can be breeding grounds for mosquitos.
Other measures involve preventing mosquito bites.
- Avoid areas with heavy mosquito activity.
- Use insect repellent when outdoors.
- Wear long sleeve shirts and pants outdoors.
- Control mosquitos inside your house.
