Within the corona-virus genera alphacoronavirus and betacoronavirus, which mainly infect  mammals, 7 out of the 15 currently assigned viral species have only been found in bats. It is proposed that bats are major hosts for alphacorona-viruses and  betacoronaviruses and play an important role as the gene source in the evolution of these two  corona-virus genera. Among the coronaviruses harbored by bats, some have drawn particular research interests, as they have been found to be associated with two high profile human disease, Severe Acute Respiratory Syndrome  (SARS)  and Middle East Respiratory Syndrome (MERS)