Street/Park
Department

Public Works Administration

Street/Park Department

Courtesy of

Communicable Disease Division of the Oklahoma State Department of Health

                   AND                    

The City of Midwest City

Public Health Fact Sheet West Nile Virus

 

·         What is West Nile virus?

West Nile virus is one of a group of viruses called arboviruses that are spread by mosquitoes and may cause illness in birds, animals, and humans. West Nile virus was not known to be present in the United States until the summer of 1999. Previously, West Nile virus was only found in Africa , western Asia , the Middle East , and Eastern Europe .

·         Where is West Nile virus in the United States ?

West Nile virus was first identified as a disease threat in the United States during the summer of 1999 and was limited to the northeastern states through 2000. However, the virus rapidly expanded its geographic range. In 2002, the largest epidemic and epizootic of West Nile ever reported occurred in the U.S. causing illness in over 4,000 people with 284 deaths. West Nile virus activity has now been detected in 44 states and the District of Columbia .

·         How is it spread?

West Nile virus is primarily spread through the bite of an infected mosquito (usually a Culex species). Mosquitoes pick up the virus when they feed on infected birds. The virus must then circulate in the mosquito for a few days before they are capable of transmitting the infection to animals or humans while biting. The virus is found in the salivary gland of the mosquito. During feeding, the virus may be injected into a human or animal where it may multiply and possibly cause disease.

·         What is the incubation period (i.e. time from exposure to time of disease)?

The incubation period ranges from 3 to 15 days for both human and equine (horse, mule, or donkey) illness.

·         What are the symptoms in humans?

The majority of persons who are infected with West Nile virus will have a flu-like illness lasting 2-6 days. Common symptoms include headache, fever, and extreme muscle weakness, occasionally accompanied by vomiting or skin rashes. In some cases, the infection will be more severe and cause meningitis, paralysis, or encephalitis (swelling and inflammation of the brain).

·         Who is at greatest risk?

Individuals are at risk of acquiring West Nile virus infection if they travel to or live in an area where West Nile Virus is known to occur. People whose work and hobbies take them outdoors for extended periods of time are at increased risk of being infected due to the increased exposure to mosquitoes. Persons over the age of 50 years appear to be at greatest risk of developing severe disease

·         How is West Nile Encephalitis treated?

There is no specific treatment. Severe cases often require hospitalization and intensive supportive care.

·         What is the state doing to monitor the spread of West Nile virus in Oklahoma ?

The Oklahoma State Department of Health (OSDH) established a statewide West Nile virus surveillance and testing program in 2001. West Nile virus was first detected in the state during July 2002. The OSDH is continuing to monitor West Nile Virus through a variety of mechanisms, including dead wild bird reporting and testing in 19 counties, equine case tracking statewide, and mosquito trapping and testing in six communities. The OSDH Laboratory offers West Nile testing for human patients through consultation with their physician.

·         Do all birds infected with West Nile Virus die?

No. The severity of the disease in birds appears to vary with the species of bird infected. Birds belonging to the Corvidae family (crows, jays, magpies, and ravens) appear to be very sensitive to West Nile viral infection and suffer a high death rate. Although mortality in a wide variety of birds has been a hallmark of West Nile virus in the U.S. , many species of birds tend to survive West Nile virus infection.

What animals besides birds and horses may develop illness from West Nile virus infection?

Birds and equine animals (horses, donkeys, mules, zebras) are most susceptible to disease caused by West Nile virus. Although numerous animals are bitten by infected mosquitoes, illness caused by West Nile virus is uncommon in domestic pets or other wildlife. West Nile virus infection coupled with disease has been rarely diagnosed in a variety of animals, including squirrels, bats, dogs, cats, goats, skunks, domestic rabbits, and even alligators. However, West Nile virus is NOT considered a significant health threat for dogs and cats.

·         Can a person become infected from handling a sick bird or horse?

There is no documented evidence of animal-to-person transmission of West Nile virus resulting from simply Continued on other side... touching an infected animal or its excretions. Because rabies may be clinically indistinguishable from West Nile encephalitis, precautions should be taken to avoid bare-handed contact with a sick horse’s saliva. Gloves or inverted plastic bags are advised to cover the hands when picking up a dead bird.

What can I do to reduce the risk of becoming infected with mosquito-borne viruses?

¨       Apply insect repellant containing 10-30% DEET (N,N-diethyl-m-toluamide) to exposed skin and clothing when outdoors, especially during  the evening and early morning hours. (Always follow labeled directions for proper use.)

¨       Prevent items such as buckets and tarps from holding standing water.

¨       If rainwater is collected, cover and seal containers when not collecting rain.

¨       Empty your outdoor pet's water bowl and refill daily.

¨       Rinse, scrub, and refill birdbaths weekly.

¨       Empty plastic wading pools weekly and store indoors when not in use.

¨       Regularly maintain swimming pools and outdoor hot tubs.

¨       Store boats covered or upside down.

¨       For a water garden or ornamental body of water, use an environmentally safe product to kill the larvae, e.g. BTI, or stock with fish that eat mosquito larvae.

¨       Regularly clean fallen leaves and debris from roof gutters.

¨       Trim grass and weeds and dismantle brush to deprive mosquitoes of a habitat.

¨       Repair or replace all broken or torn window and door screens.

·         What type of mosquitoes are in my area?

Research has shown that there is not one type of mosquito in the Oklahoma County , but several species. Each species has different breeding habits. One type may breed after heavy rains, while another becomes more abundant during droughts. All species require water for their eggs to hatch. The water may result from rain filling a debris-clogged ditch, from a swampy area near a creek, or from an artificial container like a birdbath or an old tire.

·         Where do mosquitoes live and when do they bite?

The first few days of a mosquito's life must be spent in the water, whether it is in a rusty tin can or a hole in the ground. The adult mosquitoes emerge after this larval stage. Mosquitoes like to live in moist shady places, such as tall grass or dense shrubbery, where they are protected from sun and wind and can suck plant nectars for food. The female mosquito needs protein from blood in order for her eggs to develop. This is why mosquitoes become a pest to humans. Mosquitoes seek you out because your blood is an excellent protein source.

How can I discourage mosquitoes from biting me?

You can try to discourage mosquitoes by using repellents containing Deet. Many pest mosquitoes don't travel very far to look for a source of protein. They may be breeding and flourishing in your own back yard. Some breed only in artificial containers such as wading pools or old tires. They have become a major urban nuisance. They generally bite people in the late afternoon and at dusk, while native species of mosquitoes are more likely to be nighttime biters. The native species of mosquitoes are most likely to breed in poorly drained areas along creeks and ditches.

 

·        What is the City of Midwest City doing to assist with the mosquito problem?

The Street Department will be assessing mosquito problem areas and implementing an integrated pest management program. If you call and report a problem area, the city will send a trained representative to assess the problem and suggest a possible solution. This could include the following: Suggesting a resident clean up their yard of mosquito breeding grounds and tall weeds, educating residents on breeding conditions, identifying the species of mosquito in question, treating pools of water infested with larva (if on city property).   We will also be trapping mosquitoes in order to get an accurate count of mosquitoes in a given area. These counts will then be used in deciding the proper treatment necessary for each situation.

 

·         Where can I go for more information?

Go to the Oklahoma State Department of Health web site at http://www.health.state.ok.us/program/cdd/ow/index.html for current updates on West Nile virus activity and state surveillance results, or visit the following web sites for more information:

www.cdc.gov/ncidod/dvbid/arbor/index.htm

http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html

www.epa.gov/pesticides/factsheets/skeeters.htm

www.aphis.usda.gov/lpa/issues/wnv/wnv.html

http://entoplp.okstate.edu

If you notice serious mosquito problems in your area please call the Midwest City Street Department at 739-1376 and a city representative will research the area and try to assist with the problem.  If you notice dead birds call the Midwest City Animal Shelter at 427-6640.