West Nile Virus

West Nile virus is a disease that can be transmitted to humans by mosquitoes.  While it has been common in Africa, Asia and the Middle East for decades, it first appeared in the U.S. in 1999 in New York.  It has since traveled westward across the U.S. and now is in Colorado.

It is very rare to catch this virus, and most infected people will not even get sick or will only experience mild flu-like symptoms.  However, West Nile virus can be fatal.

How the Virus is Spread

The virus is carried long distances by infected birds and then spread locally by mosquitoes that bite these birds.  The mosquitoes can then pass the virus to humans and animals, but primarily to birds and horses.

There is a vaccine for horses.  A human vaccine is being developed, but won't be available for several years.  Dogs and cats can be infected, but rarely become ill and don't spread the virus.

Mosquito season in Colorado is from late spring to mid-September.  The West Nile virus risk is highest in August and September.  The level of risk will vary from place to place even over short distances.

Health departments across the state track the virus by testing dead birds and mosquitoes and by monitoring human and horse cases.

The following measures can make summertime more pleasant by reducing the number of mosquitoes in and around the house.

Mosquito Prevention

• Limit time spent outdoors at dawn or dusk, when mosquitoes are most active.

• Wear lightweight, long-sleeved shirts and long pants while outdoors.

• Spray clothing with insect repellent containing DEET since mosquitoes may bite through clothing.

• Apply insect repellent sparingly to exposed skin.  An effective repellent will contain up to 35 percent DEET.  Use products with 10 percent DEET or less for children.

• Always read and follow product directions.

• Install or repair window and door screens to keep mosquitoes out.

Don't Breed Mosquitoes

Mosquitoes lay eggs in still water which hatch in 7 to 10 days.  If standing water is eliminated weekly, many mosquitoes will be kept from breeding in the first place.

Here are some effective things you can do:

• Remove standing water in ponds, ditches, gutters, flower pots, puddles, tires and cans.

• Check unusual items that might contain water such as wheelbarrows, hubcaps, toys, garden equipment, pool covers and plastic sheeting.  Turn these items upside down to prevent them from holding water.

• Drill drainage holes in tire swings.

• Check water in birdbaths and wading pools weekly for mosquito larvae.  Empty the water if they are present.

• Stock ornamental ponds, fountains and livestock water tanks with fish that eat mosquito larvae or treat them with BTI, a natural bacteria that kills larvae.  This can be purchased at garden and home stores or feed and supply stores.

• Do not over water lawns and gardens.

• Trim shrubbery and remove garden debris.

Risks and Symptoms

Only certain types of mosquitoes transmit the virus to people and only a small percentage of these mosquitoes carry the virus.  Most people will not become ill.  Symptoms generally appear 3 to 14 days after exposure.

All residents of areas where West Nile virus activity has been confirmed are at risk, but people over 50 seem to be especially vulnerable to severe forms of the disease.

In people who become ill, most will have mild symptoms including fever, headache, body aches, and occasionally skin rashes or swollen lymph nodes.

However, this virus can cause serious illnesses including encephalitis (swelling of the brain) and/or meningitis (swelling of the brain's lining).

Symptoms may include high fever, severe headache, neck stiffness, muscle weakness and tremors, disorientation, convulsions and coma.  Severe infections can result in permanent brain damage or, in rare cases, even death.

People with these symptoms need to seek medical attention immediately.

Finding Dead Birds

Early in the season, local health agencies track reports of dead birds and test members of the crow family (crows, ravens, magpies and lays) to find where the virus is active in the state.  Contact your local health agency for more information.

If the bird is not wanted for testing, it can be disposed of safely by picking it up with a shovel or rubber gloves, double bagging in plastic and disposing in the trash.  Dead birds should not be handled directly in order to avoid exposure to the virus.  Wash your hands afterwards.

For additional information regarding West Nile virus check out:

http://204.133.39.51/departments/health/publichealth_westnile.html