Public Health

What is West Nile Virus?

West Nile virus (WNV) is a mosquito-borne disease that can cause encephalitis or brain infection. It is historically found in portions of Africa, the Middle East, and Central Europe. In 1999, WNV invaded New York City and has since spread to all but four states in the continental United States. Nationwide last year 4,161 people became ill and 284 people died from WNV infection. However, less than 1 percent of the people infected with WNV become seriously ill. About one-third of the people infected develop flu-like symptoms and the majority of people never get sick. Two non-fatal human cases were reported in Wyoming last year but the number of human infections will likely increase as the virus continues to expand throughout the state, said Terry Creekmore, the West Nile virus surveillance coordinator for the Wyoming Department
of Health.

Mosquitoes spread this virus after they feed on infected birds and then bite people, other birds and animals. WNV is not spread by person-to-person contact and there is no evidence that people can get the virus by handling infected animals.

Surveillance for West Nile virus was initiated in Wyoming in 2001 and currently involves the reporting and testing of dead birds, and the testing of sick horses. Suspected human cases are also tested in the Wyoming Department of Health`s public health lab. People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. This is called West Nile fever. People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, and paralysis. This is called West Nile encephalitis. If you have any of these symptoms, contact your health care provider. Please see your primary care physician for more details.

About Encephalitis

West Nile virus human cases in Wyoming occur primarily in the late summer or early Fall, although the mosquito season is April through October. The majority of people who get infected with the virus have no illness, or at most, have an infection similar to a mild flu with fever, headache and fatigue. Rarely will the virus multiply in the central nervous system and cause the brain disease called encephalitis.

It can occur however. In fact, two-thirds of people who develop encephalitis or meningitis have serious long-term health problems and some people never fully recover.

Wyoming has three kinds of arboviral encephalitis: West Nile
encephalitis, Saint Louis encephalitis, and Western Equine encephalitis.

An arboviral Encephalitis is an infectious disease that affects the brain. The disease is caused by a virus which attacks and destroys some nerve cells and causes brain inflammation and swelling. Encephalitis arboviruses belong to several families of viruses that usually infect birds and are transmitted from bird to bird by mosquitoes.

What is West Nile encephalitis?

West Nile encephalitis is caused by West Nile virus, a flavivirus previously only found in Africa, Eastern Europe, and West Asia. West Nile virus is closely related to St. Louis encephalitis virus (SLEV) which is found in the United States and to the Japanese Encephalitis virus from South East Asia and to Murray Valley fever virus from Australia and New Guinea.

How can I get it?

The principle route of human infection is through the bite of an infected mosquito.

In 2002, additional routes became apparent; however, this represented a very small proportion of cases. These routes include receiving transplanted organs and blood transfusions, transplacental and possibly breast-feeding transmission, and laboratory workers working with West Nile infected products.

Who is most at risk?

Anyone can get the virus; however, people over 50 years of age have the highest risk of developing a severe illness because as we age, our bodies have a harder time fighting off disease. People with compromised immune systems are also at increased risk.

What are the symptoms?

People with mild infections may experience fever, headache, body aches, skin rash and swollen lymph glands. This is called West Nile fever.

People with more severe infections may experience high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, and paralysis. This is called West Nile encephalitis. If you have any of these symptoms, contact your health care provider.

Are there long-term consequences?

While most infections are usually mild, West Nile Encephalitis can result in death or serious brain damage. The CDC notes that neurological effects may be permanent. Some improvements may be seen over time.

Is there treatment or a vaccine?

There is no specific treatment for West Nile virus infection, nor a vaccine. While most people fully recover from the viral infection, in some severe cases hospitalization may be needed.

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How to Protect Yourself

Although mosquitoes are most active at dusk or dawn, some bite during the day. All mosquitoes will bite if you enter an area where they are resting, such as high grass or heavy underbrush. While it is not necessary to limit outdoor activity (unless there is evidence of mosquito-borne disease in the area), you can and should reduce your risk of being bitten by mosquitoes.

Common sense steps you can take to minimize the probability of infection include remembering the 5 D`s of West Nile Virus:

(1) DAWN AND (2) DUSK - When possible, avoid spending time outside at dawn and dusk.

(3) DRESS - Wear shoes, socks, long pants and a long-sleeved shirt when outdoors for long periods of time or when mosquitoes are most active. Clothing should be light colored and made of tightly woven materials to keep mosquitoes away from the skin.

(4) DRAIN - Reduce the amount of standing water in or near your property by draining and/or removing it. Mosquitoes may lay eggs in areas with standing water. See below for more information and tips on reducing the amount of standing water in or near your property.

You can also protect your family from biting mosquitoes by reducing the amount of standing water available for mosquito breeding in or near your property. To reduce standing water, consider the following:

• Repair failed septic systems.
  
• Check and repair screens on windows and doors
  
• Dispose of tin cans, plastic containers, ceramic pots or similar water-holding containers.
  
• If possible, remove old or discarded tires on your property. Used tires have become the most common mosquito breading site in the country. If you cannot dispose of old tires, you can drill holes in them to allow standing water to drain.
  
• For containers that must remain on your property, such as bird baths and wading pools, change the water at least once per week.
  
• Cover trash containers to keep out rainwater.
  
• Repair leaky water pipes and outside faucets.
  
• Aerate ornamental pools or stock them with predatory fish.
  
• Clean and chlorinate swimming pools even if they are not being used.
  
• Keep drains, ditches, and culverts free of grass clippings, weeds and trash so water will drain properly.
  
• Remove all leaf debris.
  
• Drill holes in the bottoms of all recycling containers that are kept outdoors.
  
• Make sure roof gutters drain properly. Clean clogged gutters in the spring and fall to remove leaves or other debris that may clog the drains or gutters.
  
• Turn over plastic wading pools and wheelbarrows when not in use.
  
• Clean vegetation and debris from the edge of ponds.
  
• Drain water from pool covers.
  
• Use landscaping to eliminate standing water that collects on your property.
  
• Install or repair screens for windows and doors that stay open, so that mosquitoes cannot get indoors.
  
• Place mosquito netting over infant carriers when you are outdoors with infants.

  If you know of specific mosquito control problems or problem areas, call your local city or county public works director, City Hall, or the Board of Supervisors.

(5) DEET - For additional protection from mosquitoes, use an insect repellent containing DEET (N,N-diethyl-m-toluamide). Spray clothing with repellents containing permethrin or DEET because mosquitoes may bite through thin clothing. Products containing DEET must be used properly. When Using DEET, be sure to Read and follow instructions on the label to avoid excessive use and over-application. In most circumstances products with 25 to 35 percent DEET provide adequate protection for adults.

• Apply DEET repellent to clothes whenever possible. Spray clothing with repellents containing permethrin or DEET since mosquitoes may bite through thin clothing. Apply sparingly to exposed skin, and only then if the label permits.
  
• Do NOT apply repellents containing permethrin directly to exposed skin. If you spray your clothing, there is no need to spray repellent containing DEET on the skin under your clothing.
  
• Use just enough repellent to cover exposed skin and/or clothing.
  
• Do not spray DEET directly on the face. Instead, spray repellent onto the hands and use them to apply it to the face. Remember to avoid sensitive areas like the eyes, mouth and nasal membranes.
  
• Do not apply over cuts, wounds, irritated skin, or under clothing.
  
• To find out if you have a reaction to DEET, apply the repellent to a small area of an arm or leg before general use.
  
• Avoid spraying repellents on plastic (such as watch crystals and eyeglasses), synthetic fabrics, leather, or painted or varnished surfaces. Spraying DEET on these things may cause damage.
  
• Do not spray DEET repellents in enclosed areas as the spray mist is not meant to be inhaled.
  
• Upon returning indoors, wash any treated skin with soap and water.
  
• Wash any DEET treated clothing before wearing them again. DEET products usually repel mosquitoes for several hours. However, repellents are effective only at short distances from the treated surface, so you may still see mosquitoes nearby. As long as you are not being bitten, there is no need to apply more repellant.

Apply insect repellent sparingly to exposed skin. The more DEET a repellent contains the longer time it can protect you from mosquito bites. A higher percentage of DEET in a repellent does not mean that your protection is better - just that it will last longer. DEET concentrations higher than 50% do not increase the length of protection. Choose a repellent that provides protection for the amount of time that you will be outdoors.

Products with 10 to 35 percent DEET will provide adequate protection under most conditions.

When using DEET with children, consider the following:

• Use lower concentrations.
  
• Do NOT allow children to apply DEET repellent themselves.
  
• Do NOT use DEET on infants.
  
• Current CDC Guidelines suggest that if a repellent containing DEET is used on children under 2 years of age, only one application per day should be used.

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Why do we Monitor Dead Birds?

Birds and horses typically become infected with West Nile virus (WNV) before humans, so dead birds and sick and dead horses are an indicator of WNV activity. We use animal surveillance to map the distribution and prevalence of WNV so that health and mosquito control officials are aware of it`s presence and can take whatever measures are available to mitigate the impact of WNV on human and equine populations. The idea is to identify the virus before humans are affected so that public education and mosquito control can reduce the impact.

Dead Bird Reporting

Report only dead crows, ravens, jays, and magpies.

If you find a dead bird on your property, DO NOT SEND it to state or local health agencies. Call the West Nile toll-free number at 1-877-WYO-BITE for instructions. You will be asked to provide the following information: name, phone number, bird species, number dead, address where bird found, and approximate date of death.

If the bird(s) are suitable for testing you will be advised on how to handle and submit the carcasses.

If Asked to Send a Dead Bird

Handle dead bird with gloves or put a plastic bag over your hand to pick up the carcass. Then double-bag the bird and add an ice pack if available. Place the bagged bird in a cool place but not in your refrigerator or freezer.

WNV is transmitted primarily through the bite of an infected mosquito. Persons cannot become infected through contact with an infected bird, horse, or human.

You will be advised by the person you speak with at the toll-free number on how the carcass(es) will be transported to the laboratory for testing.

Not every bird that is submitted will be tested. Reasons include bird is too decomposed, excessive birds have already been submitted from the area, bird is wrong species, etc.

Results

Results are usually available within 3 to 4 weeks. Persons will be notified ONLY IF the bird is positive.

The Wyoming Department of Health will continue to test jays, magpies, crows, and ravens from the state between May 1 and Oct. 30, 2003.

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For more information, contact:

Gus Lopez, City/County Health Director, (307) 633-4011

Terry Creekmore, Wyoming Department of Health West Nile Virus Surveillance Coordinator, (307) 742-6681, ext. 105

Scott Seys, Wyoming Department of Health Deputy State Epidemiologist, (307) 777-5596

Ross Doman, Wyoming Department of Health Public Information Officer, (307) 777-6420

Ross Doman, Public Information Officer, Wyoming Department of Health, (307) 777-6420