CLEARFIELD — A mosquito pool in Davis County has tested positive for West Nile virus.

“This marks an increase in West Nile activity,” Davis County Health Deputy Director Brian Hatch said of the virus detected last week.

“We need to be more vigilant in what we do as people,” Hatch said, He said particularly where West Nile Virus can be fatal for some.

There are no confirmed cases of the West Nile Virus in humans or horses, for which there is a vaccine, according to health officials.

The pool discoveries in Davis and Box Elder counties are not alarming, but it does mean the area along the Wasatch Front is beginning to see some West Nile activity and the public needs to take preventive measures; there is no human vaccine for the virus, Hatch said.

“It’s a concern,” Weber-Morgan County Health Department spokeswoman Lori Buttars said of the findings.

The mosquito pool testing positive for West Nile in Davis County was a culex tarsalis breeding site located in the northwest portion of the county, Davis County Mosquito Abatement District Director Gary Hatch said.

Last year the county had no mosquito pools testing positive for the virus, Gary Hatch said, but did have two sentinel chickens that tested positive for the virus.

Buttars said the discovery of the mosquito pools puts Weber County residents in close proximity to the West Nile virus, with health officials encouraging the public to avoid becoming complacent by covering up; removing standing water on their property; using mosquito repellent when outdoors and having enough repellent on-hand for friends or family who may be visiting to attend an outdoor barbecue.

A certain species of mosquito, the aedes vexans, in a lifetime can fly up to 25 miles from its breeding site, Gary Hatch said, while the culex tarsalis can travel up to about 10 miles from its host site.

Culex pipiens, the common house-mosquito, over a lifetime can travel up to about a 1 mile from its breeding ground, he said..

Mosquitoes have an average life span of two to three weeks, according to national mosquito control officials.

“Anytime temperatures are above 70-degrees,” Buttars said, “mosquitoes can breed.” It is a breeding season that will continue until the “first hard freeze,” she said. “So, it will be with us through the fall.”

In the meantime, health officials advise people to stay covered, particularly from dusk to dawn, use repellent containing DEET, and make certain all window screens are secure to prevent mosquitoes from entering the home.

Contact reporter Bryon Saxton at 801-625-4244 or bsaxton@standard.net. Follow him on Twitter at @BryonSaxton.