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

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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

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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

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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

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

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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

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