Craigslist’s entry into a market results in a 15.9 percent increase in reported HIV cases, according to new research from the University of Minnesota published in the December issue of MIS Quarterly. The study estimates that the so-called ‘Craigslist effect’ led to about 6,000 additional HIV cases a year from 1999 to 2008 in the 33 states studied, and additional treatment costs of $62 million to $65.3 million annually.
“Our study results suggest that there is a new social route of HIV transmission that is taking place in this digital era,” says Dr. Jason Chan, the study’s lead author and an assistant professor of information and decision sciences at the Carlson School of Management. “Health care practitioners and policymakers have to look more closely at online platforms to assess how its usage may facilitate the spread of HIV and STDs across the country.”
HIV/AIDS remains one of the nation’s leading public health challenges, with an estimated 1.2 million Americans living with the virus. Although the annual rate of new HIV infections diagnosed in the United States has fallen by about one-third over the past decade, an estimated 50,000 Americans still become infected with HIV each year, and about one in five don’t know it. Furthermore, even though infection rates are dropping overall, they’re still on the rise among gay and bisexual young men.
Over the past several years, anecdotal reports have raised concerns that online personals on sites like Craiglist could be facilitating risky sexual behavior and providing a new route of HIV transmission. In 2013, law enforcement arrested an HIV-positive Missouri man who had slept with more than 300 people he met on Craiglist without disclosing his status. A similar incident made the news this past August, when Oklahoma officials pressed charges against a man for using Craigslist to meet men and women for sex without alerting them that he was HIV-positive. Over a six-and-a-half year period, the man had posted at least 695 personals seeking sexual encounters, leaving health officials scrambling to identify those who may have been infected.
“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 researchers explain. “The ease of seeking sex partners through classified ad sites may promote risky behaviors that increase the transmission of STDs.”
Hoping to gain a better understanding of how Craiglist-linked sexual encounters could impact the spread of HIV on a national level, Drs. Chan and Ghose analyzed temporal data on HIV infection rates in 33 states, between the years of 1999 to 2008. Because Craigslist randomly enters individual markets with respect to HIV trends, it provided a unique natural experiment setup from which the researchers could study the connection to HIV infection rates.
For the analysis, the researchers used an econometric method that has the equivalent effect of comparing HIV trends across markets with and without Craigslist and before and after Craigslist exists in these locations. They also compared the HIV rate against the number of personal ads and contrasted it with the number of ads placed by escorts in a Craigslist section for professional services.
Emerging technology poses new public health challenges
The study found that HIV incidence began to increase about a year after Craigslist entered a market, then climbed through the study period. Dr. Chan said the one-year delay makes sense, because it takes time for the ads to reach a critical mass and for those infected to seek medical attention.
After conducting a series of tests to eliminate other possible causes that might be driving the HIV trends, such as increased testing in a community, the researchers discovered that the upward shift was influenced by ads in Craigslist’s personals sections, not the site’s escort service ads. This finding is in line with existing research that suggests internet-facilitated sex workers are less likely to participate in risky sexual practices with clients compared to people seeking sex in a social context.
Instead, it seems, the majority of new infections result from men seeking personal sexual encounters with other men. Dr. Chan suggests that may be because sexual encounters elicited through online channels tend to differ from those arrived at by old-fashioned means. Online services aggregate many different sexually available men, upping a given user’s chances and thereby lowering his fear of rejection—and creating a more nuanced market in which users can be more detailed about their proclivities (as a quick visit to a Craigslist personals section bears out). That, in turn, might modify the character of the encounter.
A prior study from the Center for AIDS Intervention Research suggests just that, showing for example that liaisons arranged online are associated with risky sexual behaviors such as unprotected, receptive anal intercourse. Not everyone agrees with that connection, however — some argue that, that while sites such as Craigslist have almost certainly increased the overall number of men having casual sex with men, the proportion of those engaged in risky behaviors has probably remained constant.
Either way, the influence that such sites have on public health is an under-researched topic. Dr. Chan’s study of Craigslist only considered data to 2008. Since then, mobile phone apps such as Grindr and Manhunt, which use GPS to help men find nearby and amenable users in real time, have become popular. Experts agree that they have probably had a similar effect on infection, but hard figures are lacking.
Indeed, the new apps may present new epidemiological concerns. Dr. Paige Padgett of the University of Texas in Houston, who is researching how people use dating apps, says that 40% of liaisons are men seeking sex with men. Because of the apps’ immediacy, she says, users don’t screen their potential partners as rigorously as they might once have done.
As researchers seek a better understanding of the way these technologies help to spread HIV, some tough questions will be raised. These may include whether health authorities should track the number of users of a service to prepare better for outbreaks of sexually transmitted diseases. There is also the issue of whether apps should carry sexual-health advice. Some already do by, for example, suggesting how better to screen partners. This removes a quandary for site owners and app developers, who might think that prominent links to HIV testing centers, for example, may put customers off. As ever, experts say having better-informed consumers is the best answer.