MERS: 5 things to know

The MERS coronavirus was first reported in spring 2012.

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MERS-CoV, short for Middle East Respiratory Syndrome coronavirus, first surfaced in Saudi Arabia in spring 2012.

So far, 262 cases of MERS have been confirmed in 12 countries, including the first U.S. case, announced Friday, health officials said. Egypt also reported its first MERS case on April 26, according to the World Health organization.

Here are five things to know about MERS:

It's a coronavirus

MERS is in the same family of viruses as SARS (severe acute respiratory syndrome -- coronavirus) as well as the common cold. However, unlike SARS, which sickened more than 8,000 people in 2003 and killed 773 worldwide, MERS does not spread easily between humans -- at least not yet.

The virus acts like a cold and attacks the respiratory system, the Centers for Disease Control and Prevention has said. But symptoms, which include fever and a cough, are severe and can lead to pneumonia and kidney failure. Gastrointestinal symptoms such as diarrhea have also been seen, according to the WHO.

The average age of MERS victims is 51, officials say, although the ages range from 2 to 94.

Researchers don't know how MERS spreads

Although all MERS cases have been linked to six countries on the Arabian Peninsula, limited human-to-human transmission has been seen among people in close contact with patients, including health care workers.

Although such transmission appears to be limited, health officials are concerned about MERS because of its virulence -- it can be fatal in up to one-third of cases, Dr. Anne Schuchat, assistant surgeon general for the U.S. Public Health Service and director of the National Center for Immunization and Respiratory Diseases, said Friday.