(CNN) -- Four more cases of a possibly fatal respiratory virus have been confirmed in Oman and Saudi Arabia, according to the World Health Organization.
Three people in Eastern Saudi Arabia contracted the Middle East Respiratory Syndrome (MERS-CoV) and one of the patients has died, the WHO said. They ranged from 49 to 83 years old and all three had underlying medical conditions. The WHO is investigating what exposure might have caused their infections.
The viral respiratory illness was first reported in Saudi Arabia in 2012 and since spread to at least four countries in or near the Arabian Peninsula, according the Centers for Disease Control and Prevention.
The WHO says it has confirmed the first case of the virus in Oman, where a 68-year-old man from Al Dahkliya region became ill October 26 and was hospitalized two days later.
Since September of last year, the WHO has confirmed 149 cases of MERS-CoV and 63 people have died from the illness.
No cases have been identified in the United States, according to the CDC. It's believed the virus has spread through close contact with ill people.
Symptoms of the disease include fever, cough, shortness of breath, diarrhea and -- in severe cases -- renal failure and acute respiratory distress syndrome with shock.
The WHO is asking member countries to carefully review any case of severe acute respiratory infections.