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Middle East Respiratory Syndrome Coronavirus (MERS-CoV) Appears in the U.S.

Medical Author: Steven M. Fine, MD
Medical Editor: Melissa Conrad Stöppler, MD

The U.S. Centers for Disease Control and Prevention (CDC) announced last week that the second and third cases of MERS-CoV, the Middle East respiratory syndrome coronavirus infection, were diagnosed in the United States. This newly recognized respiratory virus has been causing concern since it was first seen in 2012 in Saudi Arabia because it is related to the SARS (severe acute respiratory syndrome) virus that caused a deadly outbreak in 2003 and involved 800 patients, three continents, and included many secondary contacts and many health-care workers. MERS-CoV appears less likely to be transmitted from person to person than SARS, but it has a higher mortality rate of up to 36%.

MERS-CoV, formerly known as "novel coronavirus" (nCoV) because it had not been found in humans before, was first described in 2012 in Saudi Arabia and has subsequently been seen in other Middle Eastern countries. Recently, cases have appeared in Malaysia, Egypt, Europe, and the United States in travelers returning from Saudi Arabia. Secondary spread to other contacts or health-care workers outside of Saudi Arabia has not yet been described, but at least one secondary case has been identified in the United States in a person who had not travelled to the Arabian Peninsula but was in a business meeting with a returned traveler from Saudi Arabia who later was diagnosed with MERS-CoV. The secondary case was found to have antibodies to MERS, which indicated infection; however, the person was well and did not require any treatment.

Infection with MERS-CoV causes symptoms that can range from mild to severe respiratory distress, and it causes death in about one-third of cases. Patients typically complain of fevers, cough, and difficulty breathing. Some of those infected go on to develop pneumonia and kidney failure. Diarrhea has been reported in some, particularly those who are already immunosuppressed. The incubation period, or the time between exposure to the virus and development of symptoms, appears to be between three to 14 days. The source of infections is still being determined, but contact with camels (that are also known to be infected) is strongly suspected at this time. The infection has spread from infected people to other people through close contact, probably via droplets spread through coughing, although the exact mechanism of transmission is still being studied.

The CDC is monitoring the situation and is currently not advising people to avoid travel to the Arabian Peninsula; however, it is advising travelers to that region to monitor their health, wash their hands with soap and water or alcohol gel, avoid touching their mouth and eyes, and avoid contact with sick people while there. Travelers who develop respiratory illnesses or fever should seek medical attention and avoid close contact with others and further travel until well. Returned travelers who develop respiratory illnesses or fevers within two weeks of returning should seek medical attention, inform health-care personnel of their travel, cover their nose and mouth with a tissue when sneezing or coughing, and then discard the tissue.

At this time, the risk to the general population seems small as the virus has not spread easily from person to person, and most people who have been infected are people living in countries of the Arabian Peninsula, returning travelers, or their close contacts. Precautions for travelers are described above.

For more information on the travel alert see For more information on MERS-CoV, see


United States. Centers for Disease Control and Prevention. "Middle East Respiratory Syndrome (MERS)." May 17, 2014. <>.

Last Editorial Review: 5/28/2014 7:23:47 PM

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