DENVER -- West Nile virus has officially arrived in the state this year.

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A dead magpie found in Penrose, Colo. was the first animal in the state to contract West Nile virus, the State Health Department said Tuesday.

Douglas H. Benevento, the executive director of the Colorado Department of Public Health and Environment, said the reappearance of the West Nile virus in Colorado this year had been expected. But not this early.

"We had hoped that West Nile virus would not be confirmed in Colorado until at least mid-July or later this year," Benevento said. "However, this early detection does not mean that West Nile virus will be worse in Colorado this year. It just means it will be a longer season."

The season for mosquito-borne diseases typically begins around mid-July and lasts until mid-September.

Human cases are expected to follow soon.

John Pape, a department epidemiologist who specializes in animal-related diseases and who leads the department's effort to combat and control West Nile virus, said the magpie was first determined to be positive through a screening test performed at the El Paso County Health Department laboratory. A confirmatory test, which also was positive for West Nile virus, was performed Tuesday at the Department of Public Health and Environment's laboratory in Denver.

Dr. Ned Calonge, the state's chief medical officer and state epidemiologist who is based at the Colorado Department of Public Health and Environment, urged Coloradans to begin taking precautions against being bitten by the mosquitoes which carry the virus.

"The chances that any one person is going to become ill from a mosquito bite is extremely low. Although most people do not become ill, for those who do, the time between the mosquito bite and the onset of symptoms ranges from 5 to 15 days. Most individuals suffer from a fever, headaches and lethargy for 2 to 7 days before they recover.

Calonge said that people who do become more seriously ill with encephalitis as a result of being infected with West Nile virus tend to be 50 years of age and older.

"This is why public health officials continue to encourage all Coloradans, especially those 50 years of age and older, to protect themselves against mosquitoes and to reduce mosquito breeding grounds near their homes," Calonge said.

Animals in North Dakota, South Dakota, Minnesota, Michigan, Pennsylvania and several Southern states have already tested positive for West Nile virus this spring.

Last year, 14 people in the state had contracted the mosquito-borne virus but no one in Colorado died.

The virus first emerged in New York in 1999 and killed seven people. It continued to spread westward, finally hitting the Rocky Mountain states last year and Colorado on Aug. 15.

In 2002, state health officials found the disease in 380 horses, 138 birds, one cat and one sheep.

John Pape, a department epidemiologist who specializes in animal-related diseases and who leads the department's effort to combat and control West Nile virus, said the magpie was first determined to be positive through a screening test performed at the El Paso County Health Department laboratory. A confirmatory test, which also was positive for West Nile virus, was performed Tuesday at the Department of Public Health and Environment's laboratory in Denver.

Dr. Ned Calonge, the state's chief medical officer and state epidemiologist who is based at the Colorado Department of Public Health and Environment, urged Coloradans to begin taking precautions against being bitten by the mosquitoes which carry the virus.

"The chances that any one person is going to become ill from a mosquito bite is extremely low. Although most people do not become ill, for those who do, the time between the mosquito bite and the onset of symptoms ranges from 5 to 15 days. Most individuals suffer from a fever, headaches and lethargy for 2 to 7 days before they recover.

Calonge said that people who do become more seriously ill with encephalitis as a result of being infected with West Nile virus tend to be 50 years of age and older.

"This is why public health officials continue to encourage all Coloradans, especially those 50 years of age and older, to protect themselves against mosquitoes and to reduce mosquito breeding grounds near their homes," Calonge said.

Animals in North Dakota, South Dakota, Minnesota, Michigan, Pennsylvania and several Southern states have already tested positive for West Nile virus this spring.

Last year, 14 people in the state had contracted the mosquito-borne virus but no one in Colorado died.

The virus first emerged in New York in 1999 and killed seven people. It continued to spread westward, finally hitting the Rocky Mountain states last year and Colorado on Aug. 15.

In 2002, state health officials found the disease in 380 horses, 138 birds, one cat and one sheep.