A new study has linked a rise in HIV diagnoses with the emergence of Craigslist personal ads throughout the US. The research, conducted between 1999 and 2008, found that HIV cases rose in a city when Craigslist was introduced.

“Online platforms offer access to a larger social group than is generally available through offline contacts, making the internet an emerging venue for seeking casual sex partners. The ease of seeking sex partners through classified ad sites may promote risky behaviors that increase transmission of STDs,” study authors Jason Chan and Anindya Ghose write.