Syphilis is back on the rise among teenagers and millennials, a new report from the Centers for Disease Control shows. The report released last week found that the national syphilis rate increased by 19 percent in 2015, the highest rate of syphilis the country has seen since 1994.

The highest documented cases of syphilis was found in people ages 15 to 24. In all, there were nearly 24,000 cases of syphilis last year.  "The STD epidemic is getting worse in the United States and, in fact, is at its highest levels yet," said Dr. Jonathan Mermin, director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention.

Some have sought to link the growing rate of STDs to dating apps like Tinder, which give people more opportunities for more random hookups. A New York Post report published Saturday noted that online or mobile dating apps have offered young people more access to casual sex, because they are dating different people more frequently. A Vanity Fair article last year detailed how Tinder could lead to “two or three” dates a week with chances of “sleeping with all of them,” which could result in “100 girls you’ve slept with in a year.”

"The problem with casual, anonymous sex via apps is twofold: You’re more likely to catch something from one out of 100 hookups, and you’re less likely to inform your former partners if you find out you have something. Indeed, you’re unlikely to ever encounter one of them in person ever again," the New York Post wrote.

But Mermin said there's no hard evidence to show dating and hook-up apps are fueling the increase in STDs in some communities.

"The dating apps can also be vectors of prevention by increasing the amount of prevention information that people can see and also by linking people to STD and HIV testing," he said.

While it’s easy to cure if syphilis is discovered during the primary stage, if not treated accurately syphilis can move on to the secondary stage and cause rashes and large gray or white lesions named condyloma lata. Other symptoms may include fever, sore throat, swollen lymph glands, patchy hair loss, weight loss, muscle aches, headache and fatigue. Syphilis progression onto the latent, or hidden stages, can bring about the most severe symptoms, including damage to the internal organs, paralysis, numbness, dementia and gradual blindness. Women who suffer from syphilis can become infertile. The most extreme cases of syphilis can even lead to death.

Only a person with a syphilitic sore, or chancer sore, can pass syphilis on to another person. Although chancers are most commonly found on the external male genitals, vagina, anus or in the rectum, the sores can also develop in the mouth and on lips. One of the biggest dangers of syphilis is the fact that it’s hard to detect because many of the symptoms are similar to those that are usually associated with other sexually transmitted diseases.