Human coronaviruses are common throughout the world. Seven different coronaviruses, that scientists know of, can infect people and make them sick. Some human coronaviruses were identified many years ago and some have been identified recently. Human coronaviruses commonly cause mild to moderate illness in people worldwide. Two newer human coronaviruses, MERS-CoV and SARS-CoV, have been known to frequently cause severe illness.
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.
Coronaviruses are common in many different species of animals, including camels and bats. Rarely, these coronaviruses can evolve and infect humans and then spread between humans. Recent examples of this include SARS-CoV and MERS-CoV.
Most coronaviruses infect animals, but not people. In the future, one or more of these other coronaviruses could potentially evolve and spread to humans, as has happened in the past. We still don't understand why only certain coronaviruses are able to infect people.