Popular social networking websites like Facebook have been blamed for the spike in cases of syphilis as members go for unprotected sex with partners they meet on the Internet.
Official figures showed a four-fold increase in the UK in cases of potentially-lethal syphilis.
"There has been a four-fold increase in the number of syphilis cases detected, with more young women being affected," The Sun quoted Professor Peter Kelly, director of Public Health for NHS Tees, as saying.
Prof Kelly continued: "I don't get the names of people affected, just figures. And I saw that several of the people had met sexual partners through these sites.
"Social networking sites are making it easier for people to meet up for casual sex. There is a rise in syphilis because people are having more sexual partners than 20 years ago and often do not use condoms."
The highest rates were observed in women aged 20 to 24 and men aged 25 to 34, the paper said.
A spokesperson for Facebook said users should take "precautions" and be on their guard while meeting with anyone they encountered online.