MERS first appeared in humans in Saudi Arabia about two years ago. Scientists believe that it may have made the jump to humans from camels. It is a virus in the coronavirus family, making it a close relative of the common cold and of the SARS (sudden acute respiratory syndrome) virus that caused nearly 800 deaths a decade ago. Symptoms of MERS are similar to those of the common cold or flu, except that it can lead to pneumonia, kidney failure, and even death. Nearly 30% of the approximately 700 confirmed cases of MERS infection (most of them in the Middle East) have died. Transmission between humans seems to require close contact; most of the cases involve health care workers or relatives of infected patients.
A virus found in only three people in the U.S. hardly seems worth mentioning. Nevertheless, MERS is being watched closely because it is fairly deadly and because if it ever mutates to become easily transmissible (by casual contact, such as riding in the same bus), a major pandemic could ensue. For now, though, officials stress that the public is not at risk.