BOULDER, Colo. -- Boulder County has now confirmed its first human case of the West Nile virus of the year and officials are bracing for what could be a very bad year.

The victim has been identified as a 54-year-old man who was bitten by mosquitoes in his own back yard, located in east Boulder County.

His symptoms began on June 26 with a fever, "head-to-toe" rash, headache, blurred vision, loss of appetite, nausea and a sore throat, officials with Boulder County Public Health said.

Health officials across the state say they are seeing a high number of the Culex mosquito. It is a type of mosquito that easily carries the virus from birds to humans.

Also, nearly twice as many infected mosquitoes are in the Longmont area this summer. The number of mosquitoes with the disease is up 170 percent so far this summer, and it may be getting worse, officials said. This week's count is up 237 percent compared to a month ago.

"At this point and time, the positive mosquito pools are in Longmont, but that doesn't mean there's not infected mosquitoes in other areas. Most infected insects can travel 20 miles. We feel that if we are finding them in one area, it's just a matter of time," said Linda Wilson, an epidemiologist with the county health department.

Culex mosquito populations are at or above the counts observed at the same time in 2003, when Colorado experienced a large West Nile virus outbreak.

"Based on the surveillance data from around the state, the indicators are suggesting that we're heading into a high-risk year, so it's important for people to take precautions against this preventable disease now," said John Pape, an epidemiologist who specializes in animal-related diseases at the Colorado Department of Public Health and Environment.

Health officials say people should take steps to get rid of standing water and protect themselves from mosquito bites, particularly at dusk and dawn.

Boulder is the third Colorado county to report a human case of West Nile virus. Victims have also been identified in Logan and Cheyenne counties.

Infected mosquitoes have also been found in nine counties -- Boulder, El Paso, Jefferson, Larimer, Logan, Mesa, Otero, Prowers and Weld.

"Usually we don't pick up the first positive mosquitoes until around this time of year," said Pape, "but then the virus moves quickly. Due to the large numbers of mosquitoes out there now, we expect the infection rates, and therefore the human risk, to rise rapidly over the next several weeks."

"We cannot stress enough the importance of self protection," said Nisha Alden, and epidemiologist with Boulder County Public Health. "We are monitoring mosquito pools and working with municipalities to respond to high levels of mosquitoes to help protect the community, but if residents can also follow the recommendations to take precautions, it can make all the difference."

Boulder County health officials urge residents who see high levels of mosquito activity near their homes to make a report at BoulderCountyMosquito.net or by calling the BCPH hot line at 303-441-1460.

Anyone who finds a dead bird can call the Colorado Health Emergency Line for the Public (CoHELP) at 1-877-462-2911.

Nationally, a total of 26 cases have been reported in 11 states. South Dakota leads the nation with seven.

Fever, headache and neck stiffness are among the more common symptoms. In more serious cases, blindness, paralysis and inflammation of the brain have been reported.

Last year seven people died of West Nile in Colorado. In 2003, Colorado led the nation with 63 deaths and 2,947 cases. In most cases, the disease is most deadly the first time it hits an area.

Officials say four to five weeks generally pass between the time a person is bitten by an infected mosquito and the date the case is reported to the health department. This is due to the one- to two-week incubation period before the onset of symptoms and delays inherent with seeing a physician, getting test results and reporting the case. Thus, people being infected today may not be counted until sometime in early August.

"July and August are the months posing the highest risk of infection," Pape explained. "People should be extra diligent during this time and use whatever methods available to avoid mosquito bites, especially during the period from an hour before sunset through about midnight, when Culex mosquitoes are most actively feeding. We are entering the peak of the transmission season, even though only a few human cases have been reported," Pape said.