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Summer in Maine
West Nile Virus

How is the virus transmitted?
What are the symptoms?
What precautions should I take?

In less than 4 years, the West Nile virus has become a national concern. From 1999 through 2001, the Centers for Disease Control and Prevention (CDC) confirmed 149 cases of human illness from the virus, including 18 deaths. This year alone, 160 cases and nine deaths have been reported in eight states and the District of Columbia, and more cases have been documented in 30 other states. 

The mosquito-borne virus can cause encephalitis, an inflammation of the brain, and result in death. Although the first documented case of the virus in the United States was in 1999, it’s been known to exist in Africa, West Asia, and the Middle East since the 1930s. It is believed that the virus originated in Africa and was brought to this country by zoo animals. 

How Is the West Nile Virus Transmitted?

The West Nile virus is transmitted to humans through mosquito bites. Mosquitoes become infected when they feed on infected birds. After an incubation period of 5 to 15 days, mosquitoes can infect humans and animals while biting to take blood. Most cases occur in the late summer or early fall, when mosquitoes are most active.

Although birds are highly susceptible to the virus, the U.S. Department of Agriculture has also identified horses, cats, bats, chipmunks, skunks, squirrels, and domestic rabbits as potential carriers. Yet there is no evidence that you can contract the virus from handling dead or infected animals, and the virus can't be passed from person to person. The only known means of transmission is through a bite from an infected mosquito.

What Are the Symptoms of the West Nile Virus?

Only 1 of every 100 to 150 people who are infected with the virus experience symptoms, according to the CDC. Those at greatest risk for developing symptoms are people older than 50 or individuals with weak immune systems.

If you become infected, the virus could harm your central nervous system and cause inflammation of the brain, or encephalitis. Symptoms, which occur about 15 days after a bite from an infected mosquito, include:
• high fever 
• confusion 
• muscle weakness
• severe headaches. 

People who have mild symptoms or no symptoms at all do not require treatment. Those with severe symptoms may be hospitalized and be given respiratory support and intravenous fluids to help ward off such secondary infections as pneumonia. There currently is no vaccine for the virus, but several companies are working to create one.

What Precautions Should I Take?

If you live in an area where there has been a documented case of the West Nile virus, the CDC recommends that you remain calm. After all, only a few mosquitoes are infected with the virus, and chances are very slim that you will become ill from an infected-mosquito bite. Still, it is wise to take precautions. 

The CDC suggests these preventative measures to avoid infection from the West Nile virus:
• Stay indoors at dawn, dusk, and early evening, when mosquitoes are most prevalent.
• Wear long-sleeved shirts and pants when outdoors.
• Apply insect repellent to clothing and exposed skin. An effective repellent will contain 35 percent DEET; higher percentages provide no additional protection. The American Academy of Pediatrics recommends that repellents used on children contain no more than 10 percent DEET. Because the repellent may irritate a child’s eyes and mouth, avoid applying it to a child’s hands. As a general rule, don’t apply repellent to children younger than 2.
• Install or repair window or door screens to keep mosquitoes out.
• Limit mosquito breeding grounds near living areas by eliminating standing water in such places as gutters, old tires, and wading pools.



Health Information

35 Miles Street | Damariscotta, ME 04543 | (207) 563-1234