AP

Denver-area health officials say four Coloradans have been diagnosed with the West Nile virus.

The Tri-County Health Department said Friday all four patients in Adams, Arapahoe and Douglas counties were hospitalized. They are believed to be the first cases diagnosed in Colorado this year.

The Centers for Disease Control and Prevention say more than 1,100 cases have been reported in the United States in 2012. That's the highest number of cases reported by this time of the season since the virus was first detected in the United States in 1999.

Most people infected with West Nile virus won't get sick, but about one in 150 people will develop the severe form of the illness. Symptoms include headache, high fever, neck stiffness, disorientation, coma, tremors, convulsions, muscle weakness and paralysis.

Now that the virus has emerged in Colorado, Tri-County Health Department is urging the public to take precautionary measures to protect themselves. These include what the Health Department refers to as the "Five Ds:"

-Drain all standing water around the house to eliminate any mosquito-breeding sites. Flowerpots, saucers, wheelbarrows, watering can, tires and tire swings, sandbox toys and jars are among the common household items that can hold enough water for attracting and breeding mosquitoes.
-Dress in long-sleeved shirts, long pants, shoes and socks.
-Use mosquito repellents that contain DEET or picaridin while outdoors.
-Avoid outdoor activities at dusk and dawn while mosquitoes are most active.