Summer doesn't officially begin until June 21, but Health Officer Ellen Leahy with the Missoula City-County Health Department said on Monday that one summer hazard is already here.

"The mosquitoes don't know its not summer yet, so they're out," Leahy said. "West Nile virus is transmitted by mosquitoes, and as its name says, it is a virus, and there's really not a treatment to knock out the virus, so we have to be preventive, and not get mosquito bites."

Leahy said West Nile virus affects people in different ways.

"If a person is young or particularly healthy, they may not even notice if they've been exposed," Leahy said. "But, with others, mostly older folks, it can actually give you sort of a flu-like feeling with a fever, and that might go away... or it might get worse to where you're actually getting headaches and more of a central nervous response, which can be very serious. It can be fatal, but most people won't get that severe a response. But, since it is preventable, and we can't predict who might get that response, we try to keep from getting that mosquito bite in the first place."

Leahy said its best to stay inside away from mosquitoes, but, that repellant containing the chemical DEET is effective in keeping mosquitoes away.

"On children we want to use a little lower percentage of DEET, but as they get older and have a little more possibility of becoming ill with the virus, you can stand a higher level of DEET," Leahy said. "So, if you're out in the woods hiking and camping, its wet and they're eating you alive, DEET is really the best repellant there is."

Leahy said that Missoula County has had very low numbers of West Nile virus reported over the past few years. Most symptoms won't even start to show up until mid to late July.

Health Officer Ellen Leahy