Searching the Internet for medical information may not be as private as you might think.

A new study finds many health websites are using tracking systems to monitor the search terms their users are typing in, and some are also sharing that information with outside companies -- raising some serious privacy concerns, says the study authoronline tracking.An

The study, published in a research letter in JAMA Internal Medicine, is a small one. It comes from Dr. Marco Huesch, of the University of Southern California, who visited 20 popular health-related websites between December 2012 and January 2013. At each site, he typed in search terms such as "depression," "herpes" and "cancer."

He then used freely available privacy tools to detect third party online trackers such as DoubleClick, as well as commercial interception software that can trace hidden traffic from the researcher’s computer to third parties.

He found that 13 of the 20 websites had one or more third-party tracking element. Seven of the 13 also passed on search information to third parties. Those sites included, as well as news sites like The New York Times Health and Men’s Health Magazine.

Search terms done on government websites, such as the Centers for Disease Control and the FDA websites, were not leaked to third-party tracking sites. Nor were searches done on four of five sites geared to doctors, such as the medical journal websites.

Five of the 13 sites that had tracker elements also had enabled social media button tracking.

The third parties that track searches are typically companies that use the information they gather to improve the user experience or to target ads, most of which users can ignore. But Huesch, a public policy researcher, says he worries about what could happen if the data were shared and then misused.

He writes that the effects could be "embarrassment, discrimination in the labour market or the deliberate decision by marketers not to offer or advertise particular goods and services to an individual, based solely on the companies’ privately gathered knowledge.”

All the websites in the study included privacy statements that explained their policies on data sharing and that the actual identity of users would not be revealed to third parties. But Huesch believes that may not be enough and that current consumer privacy legislation needs to be strengthened.

Until then, he writes, “individuals should take care how much trust they place in their anonymity and the confidentiality of their information when online.”

Huesch is also concerned that users could become worried that their health-related Web searches could be tracked, and might lose their trust in even reputable online health sources.

“Failure to address these concerns may diminish trust in health-related websites and reduce the willingness of some people to access health-related information online,” the study concludes.