New technology used for people to find anonymous sex is making it difficult to track down and stamp out an old sexually-transmitted infection.

CBC News has learned that Eastern Health diagnosed as many people with syphilis in the first six months of this year as it did in all of 2016.

And those numbers have since risen even higher. So far this year, 29 people have been diagnosed with syphilis, already surpassing last year's total numbers by almost 50 per cent.

A briefing note obtained through access to information shows that before 2014 there were only four or five cases a year.

Health officials say there are a number of factors driving up the infection rate, and one of the main ones is lower condom use.

Lower condom usage, higher STI rates

People used to be concerned about HIV and used condoms more frequently.

But the medical officer of health for the eastern region says that's changed.

"HIV became a treatable disease," Dr. Claudia Sarbu said in an interview.

"People are not so concerned about protection and they're not concerned about acquiring [sexually transmitted infections] because there is treatment available so we see an increase in syphilis."

Medical officer of health Claudia Sarbu says fear over HIV has decreased, leading to a decrease in condom usage. (Sherry Vivian/CBC)

The vast majority of people contracting the disease are men who are having sex with men, accounting for 92 per cent of the infections.

Anonymous sex makes tracing hard

Technology is making anonymous hook-ups easier, but tracing the disease harder.

After a person is diagnosed with syphilis, health officials ask for a list of sexual contacts to notify them that they should get tested.

That's now a lot harder, thanks to anonymous dating apps like Tinder and Grindr, or websites like Craigslist.

The technology allows people to arrange hookups without trading any information about themselves.

So far this year, 29 people diagnosed with syphilis in N.L. and anonymous sex is making it hard to track its path. 2:55

At Planned Parenthood–NL Sexual Health Centre in St. John's, they see it with the clients who come in looking for testing.

"So let's say if it were that you did have a STI, then it's very hard for you to go back and figure out 'Like who was that? Do I have their number? Do I even have their last name?'" said client services co-ordinator Carla Penney.

The government briefing note shows 78 per cent of the contacts are anonymous, with no way to reach them.

That means there could be more than 150 people who've had sex with someone who has tested positive for syphilis but they don't know it.

"If the the patient can not tell you exactly the name of the person, contact information, for us it's not possible to trace down and to offer testing and treatment," said Dr. Sarbu.

Health Minister John Haggie says it's important for people to know the risks and take precautions.

"You don't know what you're going to get when you swipe right with Tinder. Other than a date you may come away with something you didn't want," Haggie said.

"The condom is your best friend."

Doctors need education

For decades, doctors didn't see cases of syphilis.

Dr. Sarbu said they're now educating family doctors about how to diagnose a disease that can often lie dormant for a long period and present with symptoms that mimic other diseases.

"Syphilis disappeared from radar for so many years," she said. "And there are younger physicians that might never (have) seen a syphilis case. So they need to update their skills, their knowledge."

Health officials say condoms are the best way to prevent sexually transmitted diseases during anonymous hookups. (MediaForMedical/UIG/Getty Images)

Doctors are also being told to encourage patients who are at high risk for the disease to get tested.

Early on, syphilis can be easy to treat with antibiotics.

But this year there have been at least four cases of neurosyphilis, which is when the disease gets into the brain and can cause vision loss, hearing loss and headaches.

Those cases are harder to treat, require hospitalization, and often leave permanent damage.

Eastern Health is trying to use the dating apps to its advantage.

In 2015, it advertised on the gay dating app Grindr, encouraging users to get tested and making it easy for people to book appointments. Dr. Sarbu says that worked well.

Eastern Health is currently surveying people people in the two age groups with the highest rates — 20-24 and 45-49 —to figure out the best way to target them.

Dr. Sarbu says they don't really understand why it's showing up in larger numbers in older men.

"There have been social changes in behaviours related to sexuality and sexual health so we need to understand those," she said.