- The Washington Times - Monday, August 4, 2003

DENVER — Colorado’s high altitude, dry climate and thin air make it ideal for 20-run baseball games and infield pop flies. But not ideal for flies or other insects.

Indeed, it’s possible to spend an entire summer enjoying the great outdoors here without getting one mosquito bite.

Many Coloradans were thus surprised to learn that their state leads the nation this year in human cases of the potentially deadly West Nile virus, a disease transmitted by mosquitoes.

This summer the state has confirmed 28 human cases, 23 of those coming in the past week. Just behind Colorado are the mosquito-friendly states of Texas, with 14 cases, and Louisiana, which has 10.

This year’s spread to Colorado marks the virus’s farthest westward migration in significant numbers. The disease has also spread to Wyoming, Montana and New Mexico, although only New Mexico has reported a human case.

Health officials attribute the surge in Colorado to an unusually wet spring, which included an unusually heavy blizzard in March, followed by an exceptionally hot July that saw temperatures in the 90s almost every day.

“We’re traditionally not a mosquito state, but we’re seeing numbers now we haven’t seen in 10 years. First the drought broke, then we had this very wet spring, and now you’re seeing a very hot summer,” said John Pape, an epidemiologist with the state Department of Public Health and Environment.

Colorado reported its first case of the West Nile virus last year, which is another factor in this year’s higher caseload. The virus tends to strike hardest in its second year, before the local bird population, which serves as the disease’s primary carrier, has built up its resistance.

The virus typically starts in birds and spreads to horses and humans through mosquito bites. Last year, 14 Coloradans contracted the disease, all of whom recovered, as well as 380 horses, 93 of which died.

“Last year, the virus was just getting its foot in the door. It’s our second year now, and that’s always been the worst for every state,” Mr. Pape said. “In Louisiana, they had their big year last year. This is their third year and you’re not seeing as much activity.”

Since it appeared in New York in 1999, the virus has moved steadily across the continent, with cases reported now throughout the South and Midwest. The disease, which typically flares up in the summer and recedes with the cooler temperatures in the fall, can prompt the onset of encephalitis, meningitis, paralysis and death.

Last year there were 4,156 cases reported nationwide, with 284 of those resulting in death. This year three persons have died from the disease: two in Alabama and one in Texas, according to the Centers for Disease Control and Prevention.

Most of the disease’s victims, however, never even know they’re sick. In 80 percent of cases, health officials say, there are no symptoms. Most of the rest will develop the far less dangerous West Nile fever and show mild symptoms — including fever, nausea and headaches — for three to six days.

One in 150 of those infected will develop the severe illness, which includes high fever, neck stiffness, tremors and coma. People older than 50 are most susceptible to developing severe symptoms, according to the CDC.

In Colorado, half the 28 reported cases have led to serious complications, including encephalitis, which is a swelling of the brain. Two victims, both of whom are older than 50, have developed paralysis in their legs that could be permanent, Mr. Pape said.

The department expects to see the caseload rise until late September, the end of mosquito season. Although most cases have been reported in rural counties, the state has also seen patients with severe symptoms in more suburban areas, including one case in Boulder.

The Bonfils Blood Center in Denver, which provides 80 percent of the state’s blood, reported last week that 37 donors tested positive for the virus. Those donors are waiting the results of a second screening, said Paige Van Riper, the center’s marketing director.

None of the donors had shown any symptoms of the virus, she said. The center began testing donated blood for the disease July 1 and has voluntarily shared results with state health officials.

“We had no idea what to expect when we first implemented the test,” Miss Van Riper said. “We’re basically doing it to protect the safety of the blood supply.”

Last week Douglas Benevento, executive director of the state health department, urged Coloradans to take precautions whenever they go outside. Those include applying a mosquito repellant with the chemical DEET and wearing long pants and long sleeves — especially at dawn and dusk, and in the forest.

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