Ralph Baric explained that the interest in viruses ~20% different from SARS1 was the result of back of the envelope math, averaging out the difference between close relatives and distant relatives that couldn’t use ACE2. Who knew nature was also interested in those same viruses??

Baric also explained that studying bookends + intermediate viruses was most useful for developing countermeasures, especially vaccines. It is strongly believed the 1977 H1N1 epidemic resulted from a failed attempt at making an attenuated vaccine. Was history repeated?