Coronaviruses are common throughout the world. Six different coronaviruses, that scientists know of, can infect people and make them sick. Some coronaviruses have been around a long time and commonly cause mild to moderate illness in people worldwide. Two newer coronaviruses, MERS-CoV and SARS-CoV, have been known to frequently cause severe illness.

MERS Coronavirus

Middle East Respiratory Syndrome Coronavirus (MERS-CoV) was first reported in 2012 in Saudi Arabia and has since caused illness in people in more than 25 other countries, including the United States. Most people reported to have MERS-CoV infection developed severe acute respiratory illness, including fever, cough, and shortness of breath. Many of them have died.

Only two patients in the U.S. have ever tested positive for MERS-CoV infection—both in May 2014. CDC continues to closely monitor the situation. More about MERS in the U.S.

Also see MERS: Guidance for Travel.

Where do Coronaviruses Come From?

Fruit bat

Coronaviruses are common in many different species of animals, including camels and bats. Rarely, these same coronaviruses can infect and spread between humans. Recent examples of this include SARS coronavirus and MERS coronavirus.

Most coronaviruses infect animals, but not people. In the future, one or more of these other coronaviruses could potentially spread to humans, as has happened in the past. We still don’t understand why only certain coronaviruses are able to infect people.