Ads showing an erupting red volcano with the words “Syphilis Explosion” over it in giant red and white letters have been popping up in subway stations and bus shelters throughout the city, and straphangers are both disgusted and very amused.

“That looks exactly like the ‘Dianetics’ cover from the 80’s!” Instagram user Jennyaborn observed, referring to the L. Ron Hubbard book.

“This makes syphilis look awesome,” wrote Instagram’s Nonvolition.

The ads, from the AIDS Healthcare Foundation, seem to depict an eruption of STDs on the scale of a biblical plague.

The ads are meant to be eye-catching, said Michael Weinstein, president of the advocacy group. “It’s like a movie poster,” he said.

The New York City population needs a wake-up call about the syphilis problem in the five boroughs: There was a 175 percent increase in syphilis cases in the state between 2012 and 2014, according to the Centers for Disease Control and Prevention.

Weinstein isn’t worried about small children seeing the ads and having questions.

“All of the studies have shown that sex education is beneficial to kids for their future health,” he said. “There’s nothing lewd about our ads.”