Researchers have long known that RNA viruses called coronaviruses cause the common cold and pneumonia. In the last two decades or so, though, researchers have found that these viruses can jump between animal and human hosts. In recent years, coronaviruses have caused lethal outbreaks of severe acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS) that span multiple continents. To date, no retroviral drug has been approved to treat these infections.
