Now, as casual hookup apps begin to replace online ads, experts worry that HIV rates might continue to rise. (Photo: Getty Images)

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.

The idea behind the HIV study arose when Chan and Ghose were researching Craigslist as a means to sell used goods. They noticed a large number of ads for one-night-stands, both in major cities — not so surprising, they thought —and smaller cities, where casual hookups aren’t quite as common. Chan and Ghose eventually focused their research on 33 states, and found that when Craigslist came to town, HIV rates rose.

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“Craigslist’s entry into a market is related to a 16 percent increase in HIV cases,” Chan tells Yahoo Health. “This maps out to an average of 6,200 cases of HIV infection in the US each year, which amounts to $62 million in annual treatment costs. We further found that the increase in HIV trends is linked with the personal ad section, not the escort section.”

Now, as casual hookup apps like Grindr and Tinder begin to replace online ads, experts worry that HIV rates might continue to rise. “With apps like Tinder and Grindr being used more and more, the likely consequence is that we will see a even greater spread of the disease,” Chan tells Yahoo Health. “However, this is only a speculation because human behavior is dynamic and can be subjected to changes over time. With the release of this study result and the increase in awareness raised about the risks involved in hooking up online strangers, individuals who use these apps might take more precautions or eliminate their current risky behaviors.”

Craigslist could not be reached for a comment.

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