Health officials are on alert for a new SARS-like virus called the novel coronavirus.
For now, most of the cases have been in the Middle East.
Nine of the fifteen people infected with the new mystery bug didn't survive.
The respiratory virus usually includes a fever and cough and can lead to pneumonia and kidney failure.
Doctors say the new bug is hard to catch and it's related to viruses found in bats.
More from CNN.com: Doctor: "People shouldn't freak out"
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