Syphilis is on the rise in Maricopa and Pima counties. And the demographic most at risk for contracting this potentially deadly sexually transmitted disease are young men and women.

Grindr, Jack’d and Tinder — social networking apps like these have made hooking up easy. Sex on your smartphone. The problem is, what happens afterward. Melanie Taylor is an infectious disease physician with the Maricopa County Department of Health.

"The increases are mainly among men, particularly gay men, but we’re also seeing an increase in syphilis diagnosis among women as well," Taylor said.

She said in 2013 there were 665 cases in Maricopa County. As of June this year, there were already 357 cases.

"So, we are projecting our numbers to be well over 700 by the end of the year," she said.

According to Taylor, that’s higher than the national average. And Maricopa isn’t the only county that’s seen a spike in syphilis. Richard May is the clinical nurse supervisor for Pima County.

"Currently this year, we’re sitting at 104 cases for 2014," May said. "In 2013 we had 55 cases and in 2012 we had 31 cases."

So far, Pima County has seen the increase primarily among men under 40. Health officials said lax sexual practices are part of the problem. At the same time, the lack of obvious symptoms means carriers may not realize they are infectious.  

"It is an ancient disease," Taylor said. "Syphilis is biblical. It’s that old and we do have antibiotics that cure the infection, but we need to make folks aware of symptoms."

And symptoms can include a lesion in the exposed area, a rash on the palms of the hands or soles of the feet. While Maricopa and Pima counties are showing an increase in the number of cases, rural counties report a decrease, according to state health officials.