There has been another confirmed case of a mysterious new SARS-like virus.
The Saudi health ministry informed the World Health Organization that a 39-year-old man was hospitalized with the novel coronavirus on February 28 and died two days later.
So far, WHO has recorded 15 confirmed cases of the novel coronavirus, including nine deaths, since the fall.
The Saudi patient did not appear to have had any contact with anyone who was already infected. As a result, WHO is investigating other potential exposure sources.
The novel coronavirus is in the same family as SARS.
SARS, or Severe Acute Respiratory Syndrome, virus sickened 8,000 people and killed 774 between 2002 and 2003.
Symptoms of the novel coronavirus include an acute respiratory infection, fever and a cough. And it could lead potentially to pneumononia and kidney failure.
The first cases were found to have occurred in an Amman, Jordan, hospital, according to the Centers for Disease Control and Prevention.
Most of the people who've caught the virus have been in the Middle East.
But there have been cases reported in the United Kingdom as well.
One of the U.K. patients had traveled to Saudi Arabia. Upon return, he infected two other family members.
"Once it gets you, it's a very serious infection," said Dr. William Schaffner, an infectious disease specialist at Vanderbilt University Medical Center in Nashville.
Fortunately, he added, the virus is "very difficult to acquire."
While the SARS epidemic was going on, many of those caring for patients were infected too. The fact that this hasn't been seen with these cases so far is a good sign, Schaffer said.
It's suspected that, like SARS, the virus originated in animals.
A study published in November found that genetically, the new coronavirus was most closely related to viruses found in bats.
While no cases have popped up in the United States, doctors say they won't be shocked if it did.
"It could happen," said Dr. Susan Gerber, a medical epidemiologist in the CDC's Division of Viral Diseases.
"That's why the CDC is working closely with the World Health Organization and other international partners."
WHO has asked member states to keep an eye out for severe acute respiratory infections and review them for unusual patterns.
It did not recommend travel or trade restrictions for countries where the virus has been found.
Dr. Susan Gerber, a medical epidemiologist in the CDC's Division of Viral Diseases, agrees.
There's no evidence of sustained human-to-human transmission, she said, "where you see a chain of many cases going person to person to person."
"People shouldn't freak out," she added. "There's no evidence that this virus is easily spread, say, across a room."
CNN's Miriam Falco, William Hudson and Elizabeth Cohen contributed to this report.