Environmental Health - West Nile Virus

What is West Nile virus?
West Nile is a mosquito-borne virus that can cause encephalitis (inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord).

How is West Nile virus spread?
West Nile virus is spread to humans by the bite of an infected mosquito. A mosquito becomes infected by biting a bird that carries the virus. You or your child cannot get West Nile virus from a person who has the disease. West Nile virus is not spread by person-to-person contact such as touching, kissing, or caring for someone who is infected.

Are older adults more at risk for West Nile viral disease?
Yes. While the chance of anyone becoming infected with West Nile virus is very low, most cases have occurred in people older than 50. People in this age group, especially the elderly, are also more likely to develop severe diseases, such as encephalitis or meningitis, if they become infected.

Where did West Nile virus come from?
Outbreaks of West Nile viral disease have occurred in Africa, Egypt, Israel, Asia, Romania, Russia and France. Before 1999, however, West Nile virus had never before been found in the Americas. The most likely explanation for its appearance here is that the virus was introduced by an infected bird that was imported or an infected person returning from a country where the virus is common.

Can you get West Nile virus directly from birds?
There is currently no evidence that West Nile virus can be spread directly from birds to people. However, dead birds can carry a variety of diseases and, therefore, should never be handled with bare hands. Use gloves to carefully place dead birds in double-plastic bags and then place in the outdoor trash.

Besides mosquitoes, can you get West Nile virus directly from other insects or ticks?
Infected mosquitoes are the primary source of West Nile virus. There is no evidence to suggest that ticks or other insects transmit West Nile virus.

What are the symptoms of West Nile viral infection?
Most people who are infected with West Nile virus either have no symptoms or experience mild illness such as a fever, headache and body aches before fully recovering. Some persons also develop a mild rash or swollen lymph glands. In some individuals, particularly the elderly, West Nile virus can cause serious disease that affects brain tissue. At its most serious, it can cause permanent neurological damage and can be fatal. Symptoms of encephalitis (inflammation of the brain) include the rapid onset of severe headache, high fever, stiff neck, confusion, loss of consciousness (coma), or muscle weakness, and may be fatal.

Is a woman's pregnancy at risk if she gets West Nile virus?
There is one documented case of transplacental (mother-to-child) transmission of WNV in humans. Although the newborn in this case was infected with WNV at birth and had severe medical problems, it is unknown whether the WNV infection itself caused these problems or whether they were coincidental. More research will be needed to improve our understanding of the relationship - if any - between WNV infection and adverse birth outcomes.

Nevertheless, pregnant women should take precautions to reduce their risk for WNV and other arboviral infections by avoiding mosquitoes, using protective clothing and repellents containing DEET. When WNV transmission is occurring in an area, pregnant women who become ill should see their health care provider. Those whose illness is consistent with acute WNV infection should undergo appropriate diagnostic testing.

How is West Nile encephalitis treated?
There is no specific therapy. In more severe cases, intensive supportive therapy is indicated, i.e., hospitalization, intravenous (IV) fluids and nutrition, airway management, ventilatory support (ventilator) if needed, prevention of secondary infections (pneumonia, urinary tract, etc.), and good nursing care.

Is there a vaccine against West Nile virus?
A vaccine for humans against West Nile virus does not exist. Horse owners should contact their veterinarian regarding a vaccine that is available for horses.

How long does it take to get sick if bitten by an infected mosquito?
Being bitten by an infected mosquito will not necessarily make you sick. Most people who are infected with West Nile virus have no symptoms or experience only mild illness. If illness were to occur, it would occur within 3 to15 days of being bitten by an infected mosquito.

What should I do if I think I have West Nile encephalitis?
If you develop signs of encephalitis, with fever, muscle weakness, and confusion, you should seek medical care immediately.

What can I do to reduce my risk of becoming infected with West Nile virus?
From May to October, when mosquitoes are most active, take the following precautions:

Avoid being outside during times of high mosquito activity, specifically, around dawn and dusk.
If outside from dusk to dawn when mosquitoes are most active, or during the day in an area where there are weeds, tall grass, or bushes, people should wear protective clothing, such as long pants, loose-fitting, long-sleeved shirts, and socks, and consider the use of an insect repellent containing DEET.

Products with a low concentration of DEET may be appropriate for situations where exposure to mosquitoes is minimal. Higher concentrations of DEET may be useful in highly infested areas or with species that are more difficult to repel. An effective repellent will contain 35% DEET (N,N-diethyl-meta-toluamide). DEET in high concentrations (greater than 35%) provides no additional protection. The American Academy of Pediatrics recommends that repellents used on children contain no more than 10% DEET. Where appropriate, consider using non-chemical ways to deter biting insects such as protective clothing (as outlined above), window- and door screens, and wearable netting when camping.

use DEET according to manufacturer's directions on the label.
As with chemical exposure in general, pregnant women should take care to avoid exposure to DEET whenever practical.
Do not allow children to handle mosquito repellent.
Do not apply DEET directly to children. Apply to your own hands and then put it on the child. The American Academy of Pediatrics recommends that repellents used on children contain no more than 10% DEET.
DEET is effective for approximately 4 hours. Avoid prolonged or excessive use of DEET. Use sparingly to cover exposed skin and clothing. Do not apply to skin covered by clothing.
Wash all treated skin and clothing with soap and water after returning indoors.
Never use repellents over cuts, wounds, or irritated skin.
Store DEET out of reach of children.
Note that vitamin B, ultrasonic devices, and incense have not been shown to be effective in preventing mosquito bites.

What can I do around my home to help reduce exposure to mosquitoes?
Mosquitoes lay their eggs in standing or slow-moving (such as streams or creeks) water. Weeds, tall grass, and bushes provide an outdoor home for mosquitoes. They can enter homes through unscreened windows or doors, or broken screens.

Make sure that doors and windows have tight-fitting screens. Repair or replace all screens that have tears or holes.
Remove all discarded tires from your property.
Dispose of tin cans, plastic containers, ceramic pots, or similar water-holding containers.
Make sure roof gutters drain properly. Clean clogged gutters in the spring and fall.
Clean and chlorinate swimming pools, outdoor saunas and hot tubs. If not in use, keep empty and covered.
Drain water from pool covers.
Change the water in bird baths every 3 to 4 days.
Turn over plastic wading pools and wheelbarrows when not in use.
Eliminate any standing water that collects on your property.
Remind or help neighbors to eliminate breeding sites on their properties.

If I live in an area where birds or mosquitoes with West Nile virus have been reported, and I am bitten by a mosquito, am I likely to get sick?
Evidence indicates that the chance of human infection and illness resulting from West Nile virus is very low. People older than 50, especially the elderly, are those most likely to get seriously ill if they become infected, and should, therefore, take the greatest care to prevent exposure to mosquito bites.

I've gotten a mosquito bite. Should I be tested for West Nile virus?
No. Illnesses related to mosquito bites are still uncommon. However, you should see a doctor immediately if you develop symptoms such as high fever, confusion, muscle weakness, severe headaches, stiff neck, or if your eyes become sensitive to light. Patients with mild symptoms should recover completely, and do not require any specific medication or laboratory testing.

Should I report dead birds to the Health Department?
State officials are interested in sick and dead crows and blue jays, - the species most often infected. These are the only species that will be tested. Birds must not be badly damaged or long dead. The bird carcass should be free of maggots and strong odor, and have intact eyes. Wear rubber gloves when handling sick or dead birds. If you have no gloves, insert your hand into a clean plastic bag, pick up the bird with the bagged hand, invert the bag over the bird and seal the bag. (Birds should be frozen as soon as possible after collection). Individuals can drop the bird(s) off at the following locations:

Kenosha County Division of Health Lab - 8600 Sheridan Road, Suite 600, 8:00am to 4:30pm. Monday - Friday.

Once 1 West Nile Virus positive bird is detected in Kenosha County, additional birds from Kenosha County will no longer be collected. However, reports of sick/dead crows and blue jays should continue to be reported to the Kenosha County Division of Health at 262-605-6700 or the West Nile Virus Hotline at 1-800-433-1610.

If a dead bird is not going to be collected, how should it be disposed of?
Dead birds can be placed in a plastic bag and be placed in the trash or garbage for disposal. Wear rubber gloves when handling the dead bird. If you have no gloves, insert your hand into a clean plastic bag, pick up the bird with the bagged hand, invert the bag over the bird and seal the bag. A shovel or other tool could be used to pick up the bird and place in a plastic bag.

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Environmental Health - West Nile Virus