About 340,000 Facebook users shared a story on the site this week about a family of five in Purdon, Texas that were all infected with Ebola and had their home quarantined. However, the story, published by a “satirical” site called the National Report, isn’t true. In fact, according to experts, that story and others like it regarding the dangerous disease represent deliberate attempts to mislead users.

Emergent.Info is a group that tracks emerging rumors and hoaxes online, and they have noticed a sharp increase in false rumors spreading on Facebook regarding Ebola.

“We’ve seen stories on satire sites — fake news sites — getting tremendous traction because they feed on people’s fears,” said Craig Silverman, the founder of Emergent.Info. “Twitter is more where rumors are birthed, but Facebook is where things absolutely catch fire, in particular when you’re talking about hoaxes and fake news articles.”

The reasons for this are unclear, though several factors are likely contributing to Facebook’s status as the preeminent platform for fake news. First, its relatively new “Trending Topics” feature encourages fake sites to take advantage of whatever topics people are already discussing in order to garner cheap clicks, shares and likes. And as The Verge points out, all content appearing on Facebook News Feeds essentially looks the same, making it harder to distinguish between real and fake news. Facebook has made some noise recently about introducing a “Satire” tag to help users weed out these hoaxes, though it’s likely that opportunistic cyber-con artists will always work to disseminate dangerously false content no matter what restrictions are put in place.