West Nile virus (WNV) is an infection caused by a virus that you can get from a mosquito bite. Most of the time the illness is mild, but sometimes it can cause inflammation (swelling) of the brain (encephalitis) or inflammation of the membranes that cover the brain and spinal cord (meningitis). The risk of serious infection is greatest for people who are over 60 years old or who have a weakened immune system.
Wild and domestic birds, mainly crows, carry the WNV. Mosquitoes get infected when they bite infected birds. The infected mosquito can then pass the virus to you when it bites you.
The virus does not spread directly from an infected bird to a human, or from person to person. Rarely, WNV can be spread by contact with infected blood, such as through blood transfusion, organ transplant, or the sharing of needles or syringes contaminated with blood. WNV may also be spread from a mother to her unborn baby. The virus might also be spread through breast milk. However, the risk of spread of the virus to the baby is believed to be very low.
The risk of WNV is seasonal in the northern states of the US and usually starts in the spring. The peak time for infection is middle to late August. In milder southern climates, the risk for infection is year-round.
Often there are no symptoms. Children are more likely to have symptoms than adults. When symptoms do occur, they usually start 3 to 14 days after a mosquito bite.
They are usually mild and last a few days. Symptoms may include:
In rare cases, when WNV affects the brain, it can be life threatening. The symptoms may include:
Your healthcare provider will ask about your child's symptoms and medical history and examine your child. Tests may include:
There is no medicine that cures WNV, and there is no vaccine to prevent it. If your child’s symptoms are mild, they will usually go away on their own. In most cases, you can care for your child at home. If the infection is serious, your child may need to stay at the hospital. At the hospital, your child may be given IV fluids, pain relievers, or other treatments.
Most people infected with WNV, including nearly all children, don’t get seriously ill, and they recover fully. Symptoms usually last 3 to 6 days, but they can last as long as several weeks or months.
If your child has a serious infection, your child may be sick for weeks or months. In the most serious cases, the nervous system or brain may be injured.
Follow the full course of treatment prescribed by your healthcare provider. In addition:
Ask your provider:
Make sure you know when your child should come back for a checkup.
Take precautions to avoid mosquito bites: