Syphilis and gonorrhea cases have spiked locally in the past five years, partly because more people are using smartphone “hookup” apps to find casual partners, Inland health officials say.

Although disease experts are still trying to determine exactly what’s causing the upswing, the recent proliferation of “hookup” apps and websites — where people can use smartphones, tablets or computers to meet up with others — is seen as a key factor.

That may be especially true for technology using Global Positioning System locators, which are making bars and parks unnecessary as casual pickup spots. That stymies public health workers trying to stop diseases like syphilis from spreading, because it’s nearly impossible to track down partners.

“The logical conclusion is that with these types of apps, people are meeting more partners. And if they’re meeting more partners, they’re more likely to have more sex,” said Tad Berman, a senior communicable disease specialist for Riverside County.

From 2010 to 2014, reported cases of syphilis rose by 147 percent in San Bernardino County. Gonorrhea cases rose by 127 percent during the same period.

In Riverside County, from 2010 to 2014, syphilis cases rose by 50 percent, while gonorrhea cases rose 121 percent.

Inland venereal increases far surpassed state hikes during the same period, when California syphilis cases rose 84 percent and 68 percent more gonorrhea cases were reported, according to county data.

In 2014, San Bernardino had 2,610 gonorrhea cases and Riverside County had 1,617. That year, San Bernardino saw 393 syphilis cases, while Riverside County had 181, according to county data.

Gonorrhea, known as “the clap,” and syphilis can be cured if diagnosed. Syphilis can cause blindness, dementia and death in later stages if untreated, according to the Centers for Disease Control.

California’s reported syphilis cases increased by 84 percent, to 3,808 in 2014, while gonorrhea rose by 68 percent to 44,974, according to County Health Status Profiles 2016, released April 4 by the state public health department.

Nationwide, the CDC reported syphilis increased by 15.1 percent between 2013 and 2014 — which the agency described as alarming — and gonorrhea rose by 5.1 percent.

Eighty to 97 percent of the syphilis cases in both counties are among men. The majority, but not all, of Riverside County’s syphilis cases in 2014 were in the Palm Springs and Coachella Valley area, which has a large gay and bisexual population.

“For us in Riverside County, the largest group at risk for both gonorrhea and syphilis are men who have sex with men,” said Carolyn Lieber, program director for the county’s HIV/STD program.

Both diseases saw large increases in all age groups from 15 to 64.

Although there is still no definitive data, disease specialists are speculating that effective treatments have eased fears of HIV, leading some people to stop using condoms or share needles.

New AIDS/HIV cases dropped over the same period in San Bernardino County, but rose in Riverside County.

However, people who take the anti-HIV pills must get their blood tested every three months, so medical professionals may be diagnosing more sexually transmitted diseases, Lieber said.

In some areas, including San Bernardino County, gonorrhea is a more heterosexual disease. In Riverside County, 993 men and 625 women were diagnosed with it in 2014.

Anonymous meetings through the “hookup” apps have stymied efforts to alert the partners of people diagnosed with the venereal diseases.

In the past, county health departments with newly diagnosed syphilis cases could send investigators to parks or bars to find people for testing and treatment, and to stop the disease’s spread.

Tracking down such partners is much more difficult with hookup technology that allows people to find partners using GPS, because the data is lost once both partners leave the location, Berman said.

“People aren’t able to give us information to find the source because, frankly, they don’t know the source,” Lieber said.