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

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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

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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

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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

A new coronavirus looks a lot like its cousin SARS under the microscope, but it appears they're quite different when it comes to contagiousness. NIAID/RML hide caption

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Coronaviruses have a characteristic crown of tentacles when viewed under the electron microscope. BSIP/UIG via Getty Images hide caption

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Virologists discovered the new coronavirus after it killed a Saudi Arabian man last summer. Elizabeth R. Fischer/Rocky Mountain Labs/NIAID/NIH hide caption

itoggle caption Elizabeth R. Fischer/Rocky Mountain Labs/NIAID/NIH

An artistic model of a coronavirus infecting a cell. The family of viruses can cause mild infections, like the common cold, and severe pneumonia-like infections, such as SARS. Peter Kohama/MCT/Landov hide caption

itoggle caption Peter Kohama/MCT/Landov

Different types of coronaviruses can cause a simple cold or a deadly respiratory illness, such as SARS. BSIP/UIG via Getty Images hide caption

itoggle caption BSIP/UIG via Getty Images

Cheryl Gleasner, a research technologist at the Los Alamos National Laboratory, works with a genome sequencing machine designed for disease surveillance. Since the SARS epidemic in 2003, advances in sequencing technologies have greatly speed up the ability to detect and track a new virus. Ross D. Franklin/AP hide caption

itoggle caption Ross D. Franklin/AP