DELAWARE COUNTY, Oklahoma - An avid outdoorsman and loving grandfather is dead after contracting Oklahoma's first reported case of the heartland tick born virus.

Family members say they can't believe his condition deteriorated so rapidly.

They want others to be aware of the danger.

In less than a week, Delaware County's Johnny Mitzner went from being vibrant and healthy to being in intensive care and unable to get out of his hospital bed.

"What happened to him was probably one of the most destructive things I've seen as a sickness goes," son Mark Mitzner said.

The sickness that ended up killing Johnny Mitzner was caused by a tick bite.

For seven years, Mark Mitzner has operated a lawn service business with his dad.

So they're always outdoors.

A few weeks ago when his dad got a tick bite, Mark Mitzner says no one thought much of it.

"Really the picture of fitness especially for his age, he was 76 but you'd think he was probably in his 40s. Full of energy, full of life," he said.

State health leaders say the tick was carrying the Heartland Virus. Antibiotics don't help, and about the best treatment option is fluids and medications for pain.

"He was having a hard time walking, feeling dizzy, kind of confusion a lot, didn't know where he was, didn't know what was going on," Mark Mitzner said.

Health leaders say it is Oklahoma's first confirmed case of the virus, and just the 10th nationwide.

"He was my hero, he was my best friend," Mark Mitzner said. "He was my partner. He was my dad. I'll miss everything."

The family wants everyone to be cautious about tick bites, especially if there are early symptoms like fever, muscle aches, loss of appetite and nausea.

"Be vigilant, be very vigilant," Mark Mitzner said. "Don't be complacent about anything crawling on your body. You might get a tick bite, [and think] ‘well it's OK. I get them all the time.' No. No more. Not for me."

The only other states with confirmed cases of the Heartland tick-borne illness are Missouri and Tennessee.