Until COVID, there were six species of coronaviruses that were known to infect humans. Four of these caused a largely benign illness in healthy people that, for most, amounted to little more than a common cold. In rare cases, these coronavirus strains could cause pneumonia. Two of the species originated from bats (alpha coronaviruses) and two from rodents (beta coronaviruses). Together these four viruses account for as many as 30 percent of upper respiratory infections in adults.45 In more recent years, two new and more fearsome human coronaviruses had emerged: SARS-1 and MERS. The new virus
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