Did they ever cancel all US-China flights during the 2003 SARS epidemic? I see that most flights were eventually canceled but I don't remember any blanket ban. If there was, it wasn't until a long time after the epidemic started, because the first WHO travel advisory for China wasn't until a good 5 months after the first case.I'm speaking on the US only but there are dozens of reasons that could have prevented massive deaths. One being clear as they did in the early 2000s when SARS broke out was to cancel all US flights in and out of China in Dec.
So far as Covid-19 goes, the first reports of a "pneumonia cluster" in Wuhan were publicly made on December 31, 2019, and we now know it had to have been circulating for at least 5 weeks already at that point. The first acknowledgement that it was a new virus was 5 January 2020 and its genetic sequence was first published on 12 January 2020.
Retrospective testing of old samples shows that Covid was already in Turin and Milan by December 18, 2019. However, Covid wasn't confirmed in Italy until January 31, 2020. By then it had already been circulating in Italy for at least six weeks.
The first confirmed Covid case in the USA was a man traveling from China to Washington on January 15. However, retrospective testing showed that a Santa Clara woman died of Covid on February 6th, suggesting that it had already gotten into Cali from China by early-mid January. And though Covid wasn't confirmed in NYC until March 6, there were already so many cases in New York (italian strain) at that point that epidemiologic modeling shows it must have arrived in New York from Italy in late January or early February at the latest.
Global air travel from China began being restricted on February 2nd, and the USA began restricting travel from many European countries on March 13th. In both cases it was far too late.
It would have been impossible for travel bans alone to stop the spread of the virus to the USA, it just got here too fast. Travel bans along with extremely good contact tracing from the beginning could have done a lot to slow the spread of the virus and maybe even caused an extreme reduction in cases, but that would have required a level of attention and competence from the government that we didn't even come close to reaching.