The current West Nile virus outbreak is the largest ever seen in the United States.

Already this year, reports say 16 people in Colorado have been infected with West Nile virus.

More than half of those cases are from the Western Slope.

Karen Martsolf, with Mesa County Health and Human Services, says, "We now have two positive confirmed human cases of West Nile virus as well as two positive mosquito pool samples that have come back positive for West Nile.”

"Right now I’m looking at eight confirmed human cases and probably tens of positive mosquito pools and I believe one horse," Bonnie Koehler, with Delta County Health Department, said.

These cases are spread across Montrose and Delta counties.

People are getting sick and there's no vaccine.

"What they do is they treat the symptoms of West Nile virus," Martsolf said.

Those symptoms mimic the flu with high fever, body ache, head ache, and chills.

"If someone is exhibiting those symptoms and thinks that they might have West Nile, it’s important just to contact their health care provider to get tested." Martsolf said.

Both Delta County and Mesa County expect more positive cases of West Nile coming in the next few weeks.

"The most important thing is for people to be mindful of the fact that West Nile is in our community," Martsolf said.

Koehler says, "Avoid dusk and dawn, drain standing water, use mosquito repellant with DEET, and dress appropriately."

Health officials say the peak season for West Nile virus will continue through the end of August, and then it will taper off as mosquitoes disappear to hibernate.