Steve Quayle News Alerts

July 23, 2003
By Jim Erickson, Rocky Mountain News

A 28-year-old Weld County man on Tuesday became Colorado's first human case of West Nile virus illness this year, while a leading expert on the mosquito-borne disease warned state residents to "be prepared for a fairly substantial human epidemic" here this summer.

The unidentified patient was not hospitalized and is recovering at his Eaton home, said Dr. Ned Calonge, the state's chief medical officer.

The man became ill July 6 and reported to health officials that he'd been bitten by mosquitoes outside his home, Calonge said.

He displayed many of the classic symptoms of mild West Nile illness, including fever, headache, muscle aches and neck stiffness, Calonge said. Blood tests completed Monday at the state health department's Denver laboratory showed antibodies to the West Nile virus, he said.

A confirmatory test will be conducted at the Centers for Disease Control and Prevention laboratory in Fort Collins. But Calonge said he is confident "this is our first case" of the year.

On Tuesday evening, Larimer County health officials reported a probable case of West Nile illness in a 31-year-old Loveland man who reported being bitten several times by mosquitoes while working outdoors in Fort Collins.

The Loveland man also became ill July 6 with severe headache, back ache, eye pain and a rash on his back and chest, said Dr. Adrienne LeBailly, director of the Larimer County health department.

The man's blood tested positive for antibodies to the virus at a private diagnostic lab in California, LeBailly said. A confirmatory test will be conducted at the state health department lab.

The man is recovering at home and was not hospitalized, LeBailly said.

West Nile was first detected in Colorado animals in mid-August last year, and the first human case was reported a month later. Colorado finished the year with 14 non-fatal human West Nile cases, along with 380 equine cases.

Last year, more than 4,100 Americans were sickened by the virus and 284 died.

So far this year, eight human West Nile cases have been confirmed nationwide by the CDC.

Human West Nile cases begin to pick up in the second half of July and drop off after fall frosts kill mosquitoes, said Dr. Lyle Petersen, acting director of the CDC's Fort Collins lab, which heads the nation's public health response to West Nile.

The fact that Colorado already is seeing human West Nile illness - along with plenty of viral activity in animals and mosquitoes - "suggests there could be a pretty substantial threat to humans in the upcoming weeks in Colorado," Petersen said Tuesday.

"That combination sets you up for an epidemic," he said.

So far this year in Colorado, West Nile has been detected in 46 batches of mosquitoes, 113 dead birds, 12 horses and 11 sentinel chicken flocks in 23 Colorado counties.

"We're only at the very beginning of the peak time, and what this means is that all of us living here in Colorado need to be especially vigilant about protecting ourselves from the West Nile virus," Petersen said.

Preventive measures include using insect repellent containing DEET, eliminating standing water where mosquitoes can breed, avoiding outdoor activities at dawn and dusk, and wearing long-sleeve shirts, long pants, shoes and socks when outdoors.

For more information on West Nile prevention, visit the state health department Web site at www.FighttheBiteColorado.com or call 1-877-462-2911.

West Nile was first detected in the United States in New York City in 1999 and has swept westward into 44 states. During its coast-to-coast march, the virus sometimes caused large outbreaks during its second year in a given state.

"What was happening was that the virus was moving into areas in mid to late season but didn't have enough time to get ramped up to cause a big epidemic," Petersen said.

"But the following year it's already there, and you have huge susceptible populations exposed to a virus that's had a chance to amplify itself in nature since the spring."

West Nile arrived in the Midwest in 2001, then exploded last summer in Illinois (884 human cases), Ohio (441 human cases) and Michigan (614 human cases).

Petersen stressed that he is not predicting a Midwest-size epidemic in Colorado this summer. It's impossible to say how many cases will occur here, he said.

But if the second-year pattern holds true, the remaining eight weeks of Colorado mosquito season could produce many human and animal West Nile cases, he said.

West Nile virus resides in wild birds and is transmitted to humans by the bite of infected mosquitoes. During last summer's drought, the virus crept into Colorado from the east along the South Platte and Arkansas rivers.

Weld County horses were particularly hard hit. One hundred of the 380 equine cases occurred there, many of them along the South Platte floodplain.

"The hot spots will be along the Arkansas and the (South) Platte rivers again, but people elsewhere along the Front Range or on the Western Slope shouldn't be complacent," Calonge said.

"We had a wet spring, and now we're seeing a hot summer with afternoon thunderstorms," he said. "That's a good setup for mosquitoes, including Culex mosquitoes."

The Culex tarsalis mosquito is believed to be the main transmitter of West Nile in the West.

After last summer's outbreak, Weld County and 21 of its cities mounted a $741,200 campaign to kill mosquitoes and reduce the West Nile threat.

Colorado Mosquito Control was hired to treat a 352-square-mile zone in southwestern Weld County.

"Not just in Weld County but all along the northern Front Range, this has been the worst mosquito season we've seen in almost a decade," said company president Michael McGinnis.

On Tuesday, Weld County health officials began "advanced discussions" with Colorado Mosquito Control about the possibility of spraying larvicide from helicopters to kill immature mosquitoes in the water, said Trevor Jiricek, director of environmental health for the Weld County health department.

West Nile cases in 2002

• Sept. 17: Commerce City man is state's first confirmed human case

• Sept. 25: Man from Prowers County and man from Weld County

• Oct. 3: 19-year-old Pueblo woman and an 18-year-old Commerce City man, son of Sept. 17 case

• Oct. 28: 42-year-old woman in Commerce City

• Oct. 29: 75-year-old Logan County man; 39-year-old Denver man; 44-year-old Jefferson County woman and 30-year-old Colorado man

• Nov. 5: Teenage Washington County girl and a 35-year-old Jefferson County man

• Dec. 15: Case in Adams County

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