Last year alone, the mosquito-borne West Nile Virus infected over 9,000 Americans and killed over 250. Already this year there have been seven deaths. And we are just entering the peak time for transmission of the disease, which is late summer, early fall. But how can you avoid a mosquito bite? Should you stay in doors at all costs? Medical contributor Dr. Judith Reichman was invited to appear on “Today” to discuss the virus, how it spreads, the symptoms, and how to prevent an infection. Here are her thoughts:
How did this virus get to the United States?
The virus has probably been around a long time, but was officially identified from an infected person in Uganda in 1937. It was later found in other countries in Africa, as well as Asia, the Middle East, and Europe, but usually caused just a mild, flu-like illness. Since the mid-Nineties, however, a more virulent strain appeared to cause outbreaks in Eastern Europe and Israel. The first known case of human infection, in this country, occurred in New York in 1999.
The virus’ life cycle involves two hosts: the mosquito and birds. Mosquitoes bite infected birds which act as the reservoir for the virus, allowing the virus to live and multiply. The infection can be fatal to the birds. It’s now found in over 170 species of birds in the U.S., but is most common in ravens, crows and jays. The virus is spread to humans by mosquitoes that bite both humans and birds. These mosquitoes are more apt to become infected in late summer, and that’s when they pose the greatest threat to us. There are now more than 43 North American mosquito species known to harbor the West Nile Virus. The virus can also live in, and cause illness or death in, chickens and horses, and has also been found in other animals, including dogs, cats, squirrels, and alligators.
Are mosquito bites the only way a person can get infected with West Nile Virus?
No. Rarely, the virus can be transmitted through blood transfusions, organ transplantation, via the placenta (if a pregnant woman is infected), and breast milk. Our blood banks currently test for the virus before donated blood is transfused.
What happens when a person is infected?
The incubation period is two to 14 days. The good news is that, for 80 percent of those infected, there will be no symptoms. But 20 percent develop a febrile (fever) illness, which may include headaches, eye pain, nausea, vomiting, diarrhea, and extreme fatigue, usually lasting only three to five days. The fatigue, however, may persist for weeks. There can also be a rash that develops on the chest, stomach, and back, and spreads outward. The most serious complication of West Nile Fever is infection of the nervous system and brain. This is most likely to occur in older individuals, or in those whose immune system is depressed from disease or cancer therapies. When this happens, mortality rates can be as high as 10 percent, and about 40 percent develop long-term neurologic problems, such as tremor disturbed balance, or Parkinson’s Disease.
Age seems to be an important contributing factor for West Nile Fever (WNF). In general, children don’t develop symptoms. The median age for WNF is the 40s, and nervous system infection increases with age. It’s 25 percent for persons older than 80.
How is WNF diagnosed?
Infection can be detected by testing for antibodies to the virus, in cerebral spinal fluid or blood. The antibodies will usually be present within eight days of onset of the symptoms.
Can West Nile infections be treated or cured?
Currently, there is no medication that has been shown to effectively treat WNF. Researchers are testing anti-viral medications and immunoglobulins, but so far the results have been neither good nor consistent. They are also working on a vaccine. If a person is severely ill, they may require “supportive care”, with intravenous fluids, ventilating machines, and prevention of secondary infection.
How can we prevent WNF infection?
There are three ways to control infection:
Mosquitoes breed in pools of stagnant water. The larvae (eggs) and/or mosquitoes, themselves, can be destroyed with products that are U.S. Environmental Protection Agency approved. These are usually sprayed or added to water by municipal authorities, once they have identified mosquito breeding grounds. Each of us can also help with mosquito control by emptying stagnant water in flowerpots, rain gutters, pet bowls, buckets, barrels, and cans. We should alert local authorities to potential mosquito-breeding sites, such as sewers, ditches, and abandoned properties, with standing water.
Mosquito bite prevention
- Avoid mosquito-infested locations.
- Wear long-sleeved clothing and pants.
- Use mosquito repellent.
There are a lot of products that claim to help prevent bites. What are the most effective?DEET products, containing 10 to 50 percent DEET are still the best. This concentration is sufficient, under most conditions, to prevent bites and WNV infections. Read the instructions carefully, and re-apply as directed. Pregnant woman should use repellent on their skin and clothes, if and when they are exposed. As for children, the American Academy of Pediatrics recommends that repellants containing no more than 10 percent DEET should be used. DEET can also be applied or sprayed onto clothing, tents, bedrolls, and screens.
Botanical repellants have, in general, shown very little, or no protection. Repellant impregnated wristbands have not been shown to work, and the popular Skin-So-Soft Bath Oil has, in a study published in the New England Journal of Medicine, been found to provide less than 10 minutes of protection from a certain type of mosquito bite.
Since there is no current treatment for WNF, we all have to stand guard (or use some form of guard), to prevent and control its spread. We need to be good citizens, and report breeding grounds, as well as suspicious deaths of birds and animals, to our local authorities… birds falling out of the sky are not a normal occurrence! (You can go online for the Center for Disease Control, or CDC, to find out where to make these reports.)
Remember: Any mosquito may harbor a virus that originated in a far off land, knows no boundaries, and has no cure. Precaution and prevention are paramount.
Dr. Judith Reichman, the “Today” show's medical contributor on women's health, has practiced obstetrics and gynecology for more than 20 years. You will find many answers to your questions in her latest book, "Slow Your Clock Down: The Complete Guide to a Healthy, Younger You," published by William Morrow, a division of .
PLEASE NOTE: The information in this column should not be construed as providing specific medical advice, but rather to offer readers information to better understand their lives and health. It is not intended to provide an alternative to professional treatment or to replace the services of a physician.