They’re here.

There’s no official confirmation, and no one knows how many. But officials with El Paso County Public Health say mosquitoes carrying the West Nile virus are almost certain to be in the area, especially with a confirmed human case in nearby Fremont County.

“My assumption, since we have some evidence that there’s mosquito activity as close as Fremont, is that it’s probably in El Paso County as well,” said Dr. Bill Letson, medical director for El Paso County Public Health.

Unlike some of Colorado’s largest counties, El Paso County no longer does mosquito surveillance or treatment. The county health department eliminated its mosquito control program several years ago because of budget cuts.

But Susan Wheelan, communication director for El Paso County Public Health, said testing is not critical, because West Nile season comes along every year, like flu season.

“We don’t test because we know it’s here, so we push prevention” she said. “We know West Nile virus is not going away; the risk is not zero.”

This year, Colorado has escaped the dramatic rise in cases that is plaguing Texas and four other states, most of them in the South. The five states account for 75 percent of the 1,118 cases that had been reported to the U.S. Centers for Disease Control and Prevention as of Wednesday. It’s the highest number reported to the CDC at this point in the summer since West Nile virus was detected in the U.S. in 1999, the CDC says on its website, and three times the usual amount.

Forty-one people have died from the virus this summer.

Only five cases have been confirmed in Colorado — one each in Fremont, Weld, Delta and Mesa counties. An additional seven could be added to the list next week if the cases are confirmed, said Elisabeth Lawaczeck, the state public health veterinarian with the Colorado Department of Public Health and Environment.

The virus tends to be cyclical, Lawaczeck said, and the conditions that favor mosquito breeding have hit some of the most affected states, but public health officials have not pinpointed the reason for the spike in cases. And Colorado could just as easily be on the CDC’s list of most-affected states in future years, though Lawaczeck doubts the numbers will climb as high as they did in 2003, when Colorado led the U.S. with 2,947 confirmed cases and 63 deaths.

“Just because the numbers are not high this year doesn’t mean we couldn’t have a year like Texas is seeing,” Lawaczeck said.

West Nile virus is transmitted to humans via the bite of female mosquitoes that have fed on infected birds. But a bite from an infected mosquito rarely leads to illness. Letson notes that 80 to 90 percent of people who are bitten will not have symptoms. An additional 10 to 20 percent will get West Nile fever, with symptoms that include fever, headache, body aches, nausea, vomiting and swollen lymph glands. They can feel fatigued for months, Lawaczeck said.

About 1 in 150 people will come down with much more serious manifestations of the virus: West Nile encephalitis and meningitis. Those most prone to the serious, and sometimes deadly, conditions include the elderly and people with compromised immune systems.

Lawaczeck also reminds horse owners to get their horses vaccinated against West Nile. Five horses have tested positive for the virus this year.