America's death toll from West Nile virus has risen to eight so far this year.

The latest victim is a 67-year-old woman in Boulder, Colorado, who had encephalitis. Lab tests confirmed the virus.

She was the fifth person to die from West Nile in Colorado thus far this year. Twelve new cases are reported in the state, although health officials think the actual number may be higher.

West Nile was first detected in Colorado last summer, infecting 13 people but killing none. This year, the state leads the nation with 166 human cases.

The only known link among the fatalities is their ages, all were elderly. A Boulder health official says people 50 and over face a greater risk of dying from West Nile.

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West Nile virus Facts

• The West Nile virus is a mosquito-borne virus that can cause encephalitis (an inflammation of the brain) or meningitis (inflammation of the lining of the brain and spinal cord) in humans and other animals.

• The virus is named after the West Nile region of Uganda where it was first isolated in1937.

• The virus appeared for the first time in the United States during a 1999 outbreak in New York that killed seven people.

How is the West Nile virus Spread?

• The virus is spread to humans, birds and other animals through the bite of an infected mosquito.

• A mosquito becomes infected by biting a bird that is carrying the virus.

• West Nile virus is not spread from person to person, and no evidence indicates the virus can be spread directly from birds to humans.

• Only a small population of mosquitoes are likely to be infected and most people bitten by an infected mosquito do not become sick.

• 1 in 300 people bitten by an infected mosquito get sick.

• 1 in 100-150 who get sick become seriously ill.

• 3 to 15 percent of those seriously ill die.

Symptoms of the Virus

• The symptoms generally appear about 3 to 6 days after exposure. People over the age of 50 are at a greater risk of severe illness.

• Milder symptoms include: Slight fever, headache, body aches, swollen glands and/or sometimes a skin rash.

• Severe symptoms include: High fever, intense headache, stiff neck, and/or confusion.

Protecting Yourself

• Control mosquitoes from breeding around your home. Remove standing water from any item or area that can hold water. Standing water is a perfect breeding place for mosquitoes.

• Wear long and light colored clothing.

• Use insect repellent products with no ore than 20-30 percent DEET for adults and less than 10 percent for children.

• Spray repellent on your hands and then apply to your face; spray on clothing, as well. Be sure repellent is safe for human skin and clothing.

• Wash off repellent daily and reapply as needed.

• Stay inside at dawn and dusk because that is when mosquitoes are most active.

Source: www.vdh.state.va.us contributed to this report