Saudi Arabia said yesterday another person has died of the SARS-like illness that's killed a total of nine people since last fall.

The World Health Organization records 15 confirmed cases of the novel coronavirus with most cases occurring in the Middle East, but a few in the United Kingdom after a man returned from a trip to Saudi Arabia and infected two others. The first two cases occurred in Amman, Jordan, said the U.S. Centers for Disease Control and Prevention.

The novel coronavirus is similar to SARS, or Severe Acute Respiratory Syndrome, which struck 8,000 and killed 774 from 2002 to 2003. The virus presents with an acute respiratory infection, fever and cough, potentially causing pneumonia and kidney failure.

"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, as reported by CNN. Fortunately, he added, the virus is "very difficult to acquire."

In this case, a 39-year-old man died in late February two days after going to the hospital, with no apparent contact with others infected with the virus. Investigators said they're trying to determine the source of the infection but note the disease does not easily hop from person to person.

"There's no evidence of sustained human-to-human transmission," said Dr. Susan Gerber, a medical epidemiologist with the CDC. "Where you see a chain of many cases going person to person to person."

Gerber said the disease could potentially reach the United States, however.

"That's why the CDC is working closely with the World Health Organization and other international partners."

The journal Nature reported last week that scientists have identified the molecule receptor the virus uses to infect human pulmonary systems. The target receptors are found deep in the lung tissue, which might explain why the disease doesn't spread easily by cough and sneeze. Researchers quoted by Nature said they lack enough epidemiological data about the disease to make too many conclusions, however.

As epidemiologists continue to investigate the reservoir and transmission of the disease, the CDC said the virus is most closely linked to a coronavirus found in bats.