3 Things You Need to Know About West Nile Virus

What and Where is West Nile Virus?

West Nile Virus (WNV) is an arthropod-borne virus (arbovirus) spread most frequently through the bite of infected mosquitoes (Culex sp.). Mosquitoes become carriers of WNV after feeding on infected birds and can then transmit the virus to humans through subsequent bites. WNV is found worldwide, and is considered endemic in the United States. While previously rare, it is now the most common arboviral infection in the United States. ArboNET, a national arboviral surveillance network managed by the CDC and state health departments, can provide up-to-date information on cases of WNV in the United States. 

WNV may also be transmitted through blood transfusions, organ transplantation, or very rarely from mother to baby during pregnancy, delivery, or breastfeeding. WNV is not spread through casual person-to-person contact.

What are the symptoms?

Most people (about 80%) infected with WNV do not show any symptoms and recover completely as their immune systems fight off the virus. However, for those who do develop symptoms, they may appear within 2-14 days (generally 2-6 days) after infection. These symptoms often resemble those of a mild flu, including fever, headache, nausea, fatigue, and possibly a transient blanching rash. While WNV can affect any age, children are less likely to have the severe forms of presentation, unless they have other risk factors (immune compromise from cancer or organ transplantation). 

In rare cases (less than 1% of infections), severe illness can occur, affecting the brain or spinal cord, resulting in conditions like meningitis or encephalitis. Symptoms of severe WNV infection may include sudden high fever, severe headache, stiff neck, confusion, muscle weakness, tremors, seizures, or nausea and vomiting. Rarely, WNV may cause acute flaccid myelitis (a paralysis-like syndrome) or other facial nerve palsies (weakness in the facial muscles). 

Call your child’s doctor right away if you notice any of these symptoms. Hospitalization may be needed for supportive treatment including intravenous fluids, pain medication and nursing care.

How can I prevent it?

Currently, there is no vaccine or specific antiviral treatment for WNV, so prevention is key:

• Use mosquito repellent: Using a protective barrier on skin such as an insect repellant with 30 percent DEET (American Academy of Pediatrics) can help to repel mosquitoes. This strong protective barrier requires extra precautions. Avoid application of DEET on the hands of children, over cuts or wounds, or on clothing. Apply sunscreen before repellents, and avoid combination products as sunscreen needs to be replied more frequently. Bathe your child with soap and water and rinse with clean water to remove repellent before he or she goes to bed. The EPA provides updated guidance on insect repellents, and information can be found here. 

• Dress for protection: Encourage your child to wear protective clothing to prevent mosquito bites while playing outside. If weather permits, wearing long sleeves, long pants and socks can add an additional barrier of protection. An additional protection is application of permethrin to clothes, effective through multiple washes (avoid application to skin). Both DEET and permethrin have been proven to repel ticks (and to kill ticks in the case of permethrin). 

• Reduce mosquito exposure: The mosquitoes that spread WNV are most active from dusk to dawn, especially 1-2 hours before sunset. During these times, parents should take extra precautions and consider keeping children indoors if possible. Use screens on windows and doors to keep mosquitoes out of the house. Eliminate standing water around the home (e.g., in flowerpots, buckets, birdbaths) as these are breeding grounds for mosquitoes.

For additional bug repellent tips, click here or to learn more about mosquito-borne diseases, click here.