Mild winter may spur West Nile virus in Utah

Utah's West Nile virus season appears to be off to an early start, with the weather setting up conditions similar to 2006 — when 158 illnesses and five deaths were reported around the state.

Gary Hatch, a manager at the Davis County mosquito abatement district, said he is "very concerned" with the greater population of virus-carrying mosquito larvae found in water samples, a surge caused by the combination of a mild winter and warm spring.

"As far as I can remember, this is the earliest we have ever detected them in the water, which means the season is starting early," Hatch said. "Right now, we are probably two to three weeks ahead of where we normally would be this time of year."

Sam Dixon, a manager at the Salt Lake City mosquito abatement district, said the preliminary rate of mosquitoes discovered with the virus so far this spring is similar to numbers found during the epidemic in 2006. But he added that only time will tell if West Nile will be reintroduced to the Salt Lake Valley in force.

"This is just upping the ante," Dixon said. "We're just that much earlier in the season."

Utah Department of Health officials are encouraging residents to use safeguards as the virus season approaches: get rid of standing water, wear mosquito repellent that contains DEET and wear long-sleeved clothing for added protection from dusk to dawn.

No human cases of West Nile have been reported in 2012, "but that doesn't mean that it's not out there," said JoDee Baker, an epidemiologist for the department. "We want to make sure that people take the proper precautions."

In Davis County, abatement district staff begin spraying for mosquitoes in early April, but normally don't detect larvae carrying the virus until late April or early May, Hatch said. West Nile-positive larvae were found in water samples this season on April 9, the earliest in his 18 years in Davis County.

"Some of the numbers we are seeing right now are what we would be seeing mid-June," Hatch said.

In 2011, three cases of the virus were reported in humans, with one person falling ill in each of Salt Lake, Tooele and Cache counties. One infected horse was reported, along with 25 infected mosquito pools, according to a 2011 department report on West Nile trends.

No human fatalities have been reported in Utah since 2007, when two deaths were attributed to the virus.

Most people who contract West Nile will not have symptoms, while about 20 percent will get flu-like symptoms.

About one out of 150 of those infected will have more severe symptoms, including disorientation, muscle weakness and a stiff neck. In rare occasions, these people may have seizures, go into a coma or die. People over the age of 50 are the most susceptible to more severe symptoms, according to the department.

Dixon said he recommends Utahns repair holes in screens on doors and windows and change out standing water in backyard containers at least once a week. He said the West Nile-carrying mosquitoes only bite from dusk until dawn.

Hatch said he recommends people consider Picaridin repellant as well as DEET, and said the mosquito district will provide fish to eat mosquitoes for backyard ornamental ponds.

The mosquito district fish request form for Davis County can be found on http://www.davismosquito.org/fishrequest.htm or residents can call 801-544-3736 for more information.

In Salt Lake City, residents can call 801-355-9221 for more information. —

Learn more about West Nile

Visit the Utah Department of Health's information page.

See a national map of 2011 human cases of West Nile.