by M. Shendrikar MD MPH
What is it?
West Nile Virus (WNV) is a virus that was originally discovered in Uganda, west of the Nile River. It is a common viral illness in Europe, Africa, Asia and Australia. It made its way to the United States in 1999 when the first known cases were documented in New York City. It has since moved its way westward across the US. Cases have been reported in almost all contiguous states, including California.
How is it spread?
WNV is carried by mosquitoes and birds. The only way to transmit WNV is via a mosquito bite. The mosquito must bite a bird that has WNV in order to be infected. Then, that mosquito must bite a human or horse in order to pass the infection along. It is not contagious amongst humans or horses. The only other ways to get WNV is from a blood transfusion (although the blood banks are aware of it and are screening the blood), organ transplantation, via mother to fetus and from breastmilk.
What does it cause?
For the most part, people infected with WNV will develop a flu-like illness between 3 to 10 days after a suspected mosquito bite. Most people will not know that the cause of their “flu” is due to West Nile. Actually, only 1 in 5 people will have symptoms of infection. Symptoms of infection include fever, muscle aches, fatigue, nausea, vomiting, chills, cough, headache, and possibly joint aches. This illness is called West Nile Fever. It may last up to 2 weeks, just like any viral syndrome.
Only 1 in 150 infected people will have severe disease. Those who have severe disease will have persistent fever, headache, neck stiffness, paralysis of their arms or legs, and may not be easily arousable. This is a serious version of the illness and patients should be taken to the hospital to have more tests done. People with severe disease may have an inflammation of the brain and/or spinal cord called encephalitis or meningitis. This illness is called West Nile Encephalitis. Reports in the news of deaths from WNV are from progression of the illness to the encephalitis stage.
When am I at risk?
The late summer months and early fall are the times that infection is most likely, although it has been reported in the spring in some states. WNV will likely become a part of the numerous other diseases that we have on a regular basis.
Young, healthy people under age 50 are at risk for WNV and West Nile Fever, but are very unlikely to develop West Nile Encephalitis. Elderly, immuno-suppressed people (such as those with cancer, HIV, lymphomas) are at higher risk of developing more severe illness once they have WNV.
What can I do to protect myself and my children from it?
Always use mosquito repellent when outdoors and mosquito nets or screens if you are at risk when you are indoors. The most effective mosquito repellants contain DEET, which is safe for pregnant/breastfeeding mothers and children over 2 months (read the labels). There are different brands that contain varying amounts of DEET, use the smallest amount of DEET for infants and children. If you need to use sunscreen and DEET, put the sunscreen on first. Always use as directed, you may need to reapply the repellant. Skin So Soft by Avon and other non-DEET repellants are not as effective as DEET preparations.
Limit outdoor activity at dusk which seems to be the time that mosquitoes begin to look for a blood meal! Remove all stagnant water around your property since the mosquito’s life cycle depends on still water. Place pets’ water bowls indoors during primetime mosquito season.
What tests and treatments are available?
Unless you have the encephalitis, there is no need to check the blood for WNV. There are experimental clinical studies underway for treating West Nile Encephalitis, but so far, there are no FDA approved treatments.
Just like any viral illness, people who have West Nile Fever should take plenty of salt and sugar-containing fluids, such as chicken broth, Gatorade, water, pedialyte. For headache and fever, medications such as acetaminophen (Tylenol) or ibuprofen (Motrin/Advil) should be taken. If someone is extremely dehydrated, intravenous fluids may be needed. If someone has West Nile Encephalitis, stronger pain medication may be needed to control headache. If the illness worsens, they may require hospitalization.
What about the birds?
You may notice more dead birds in the area. Many birds may have the virus and many of them will die from the infection. If you see a dead bird in your area, contact your local health department. In the county of Los Angeles, you may call (213) 620-2380 for the Health Department.