TULSA, Oklahoma - The Tulsa Health Department was notified Thursday that a man over the age of 65 was diagnosed with West Nile virus.

The state health department said the first confirmed case this year was a man in Pittsburgh County. They also have three cases under investigation, including the Tulsa County man and two others from unspecified counties.

Just within the last week, mosquitoes started testing positive for West Nile Virus in Tulsa County. 

Environmental specialist Scott Meador is testing mosquitoes from some of the 75 traps spread out across Tulsa County.

"It's really hard to determine where a positive will come up," Meador said.

Last week was the first round of tests this year for the Tulsa County Health Department.

That's when mosquitoes in nine areas tested positive for West Nile Virus.

"I was surprised to find so many. I did a retest just to verify; brought in another environmental specialist just to verify," Meador said.

Last year, the health department only had one or two areas test positive for the entire season.

Jon Baker, from the Tulsa County Health Department said this year should actually be considered a normal season.

"We've had about a three-year lull in West Nile Virus activity from humans and mosquitoes and, for whatever reason, this summer, it looks like it's going to pick back up," Baker said.

The nine traps that tested positive were split among two locations in Midtown and South Tulsa. The first is between Pine Street and 41st Street South and east of the Arkansas River to Memorial. The second area is between 71st Street South and 111th Street and from the Arkansas River to Memorial.

Oklahoma first saw West Nile Virus in 2002.

"It's just really not enough timeline to help us understand why it's here now and it wasn't here a couple, three years ago," Baker said.

The Tulsa County Health Department tests every week by grabbing mosquitoes from the trap, adding a solution and copper pellets, and then grinding up the bugs.

This releases any possible West Nile Virus fluid in the mosquitoes.

Then a testing strip indicates with two red stripes for positive, or one red stripe for negative.

Meador said, "We could have a rash of positives one week and not see any more positives the rest of the year."

That's the hope, but the health department will spray for West Nile, in the meantime.

Remember to wear bug spray when you're outside, and get rid of standing water around your home.

You can call the health department to request mosquito spraying in your area by calling 918-595-4219.