Is this virus like TB and smallpox (stay deadly for a long time) or flu (ceases to be a killer after a few years)?
Think of these pathogens as evolving around niches.
Influenza mutates readily. That is an advantage for the niche it occupies: infect a lot of people, don't kill too many since dead people don't spread it. But the mutations aren't guided by any master plan other than random genetic change. So deadly flus arise. They naturally become attenuated because mutations that result in mild cases get passed on, lethal mutations are self limited. Those mutation branches die out.
TB is a bacteria, very slow growing. Mutations tend toward developing antibiotic resistance. There is no genetic mechanism favoring mutations to milder disease. Like with HIV, you can infect a lot of people before you die. No selection pressure to get weaker, but clear selection pressure to develop drug resistance.
Small pox was before my time so I know less about it. It has typically had about a 30% fatality rate. Maybe that was a steady state, I'm just guessing.
Generally speaking the population that got infected is the one that selection pressure affected. TB is similar. Populations with generations of coexistence developed resistance. Human genetic change develops very slowly.
Unless you wipe out 95% of a population. Then people with genetic resistance that survive such epidemics have offspring with some of the resistance. Such is what happened with Native Americans and smallpox, first a lot of them died, later not so many.
This happened with rabbits in Australia. Humans thought bringing a deadly rabbit virus to the continent would solve the rabbit problem. Rabbits reproduce rapidly. So that ~5% that survived rapidly reproduced and voilá, you have a high level of resistance in the rabbit population.
With TB: Pacific Islanders and Native Americans still have greater susceptibility to disease if they get infected. Not enough generations yet since their population was exposed to TB.
Back to coronavirus, it has a moderate mutation rate, not as fast as flu, but faster than say measles. So it will naturally attenuate if we don't stop it altogether.
BTW, one reason viruses like measles don't mutate as much is because vaccines prevent the virus multiplying. That lowers the mutation rate. Before the vaccine, new crops of kids were born allowing the virus to go on being deadly but not so much it wiped out its host.
That will never happen with flu vaccines because the reservoir is much too huge.
Bottom line, there is no one size fits all and resistance is a very complicated thing.
One person infecting 61 other people! That is one infectious virus. If other passengers catch it from these 61 people then society has a major problem. If the rest of the passengers are safe then so is society.
Depends what his job was. Could be he made the salads or something. He also could have had very poor hand hygiene. Maybe his job was to greet guests and shake their hands.
Another possibility is those 61 people were out of a couple thousand potentially exposed. That might mean it was not very contagious.
