A farmworker in Riyadh, Saudi Arabia, wears a mask to protect against Middle East respiratory syndrome earlier this month. The MERS virus is common in camels. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Fearful of catching the MERS virus, workers wear masks during a soccer match on April 22 at King Fahad stadium in Riyadh. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Jockeys take their camels home after racing in Egypt's El Arish desert. The annual race draws competitors from around the Middle East, including Saudi Arabia, where camels carry the Middle East Respiratory Syndrome virus. Nasser Nouri/Xinhua /Landov hide caption

itoggle caption Nasser Nouri/Xinhua /Landov

Camel jockeys compete at a festival on the outskirts of Saudi Arabia's capital Riyadh, a focal point for the Middle East respiratory syndrome virus. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

The source? Signs of the Middle East respiratory syndrome virus have been detected in camels on the Arabian Peninsula. But it's still a mystery how people catch the disease. Sean Gallup/Getty Images hide caption

itoggle caption Sean Gallup/Getty Images

So cute, but not cuddly. The Egyptian tomb bat, Taphozous perforatus, is a likely carrier of the Middle East respiratory syndrome virus, or MERS. Courtesy of Jonathan H. Epstein/EcoHealth Alliance hide caption

itoggle caption Courtesy of Jonathan H. Epstein/EcoHealth Alliance

A dromedary camel waits for a tourist to hop on its back in Petra, Jordan. The country has recorded two cases of the Middle East respiratory syndrome. Chris Jackson/Getty Images hide caption

itoggle caption Chris Jackson/Getty Images

Saudi men walk to the King Fahad hospital in the city of Hofuf on Sunday. In eastern Saudi Arabia, where outbreaks of the MERS virus have been concentrated, people have resumed their habits of shaking hands and kissing. Fayez Nureldine/AFP/Getty Images hide caption

itoggle caption Fayez Nureldine/AFP/Getty Images

Here's the coronavirus that appears to have originated in the Middle East and has caused severe illnesses in people living there and in Europe. AP hide caption

itoggle caption AP

A nurse walks towards the Roger Salengro Hospital in Lille, France, where two patients were diagnosed with a coronavirus related to SARS. Michel Spingler/AP hide caption

itoggle caption Michel Spingler/AP