But as it turns out, there's a lot we stitu don't know about MERS. It was only discovered in 2012, and the countries that previously harbored the virus, like Saudi Arabia, haven't always been transparent about their findings. Experts still don't understand exactly how MERS is transmitted, which is worrisome. And the fact that the disease is a deadly respiratory infection, from the same family as SARS (which infected more than 8,000 people during a 2003 global pandemic), has health officials on guard.