I think it is also incorrect to try to take how the virus spread in China in winter and assume it would have followed the same trend in summer.
If covid19 started in Europe in March19, then a lot of early case would have been in spring, and could have easily be chalked off as seasonal flu to start with.
Given the lower population density in Europe, it could be that by the time it achieve much in the way of numbers of infections, it was already summer, which helped to naturally suppress the spread and effects of the virus. Just look at the death rates worldwide over the summer months compared to the initial surge.
Please keep in mind that the pandemic in the US started in April and May and plateaued in July and August. Especially here in Texas, where we have 100 deg F and 100% humidity in July and August, our worst month of the pandemic was in the hottest month in summer when we had 15,000 cases in a single day in Texas alone. And this was after almost a month and half of lockdowns in most major cities in Texas. And Texas is very sparsely populated. This particular coronavirus doesn’t care about summer too much.
Also, the first wave of the pandemic overwhelmed hospitals in Europe in March to May and June 2020. This would be the same period in 2019, when you assume the virus somehow become a lame duck in Europe even without any kind of human intervention.
Also, about the assumption that somehow the virus acquired a crazy mutation to be super contagious when it got to Wuhan. So far, I haven’t heard anything about any significant genomic differences between the European strains detected in 2019 and the Chinese strains detected in 2020. Further, mutations don’t necessarily mean changing function. It’s been almost a year since the virus was first detected in Wuhan. Genomic analyses have shown that the virus has undergone many mutations. None of the new mutations have made the virus any more or less contagious. Although some have hypothesized that certain mutations have changed how the virus behaves, they lack concrete evidence to support their hypothesis. So pretty much the virus has stayed the same all this time. What are the chances that the virus made a huge mutation when it got to Wuhan? Slim to none. Again, we have no evidence that the European strains detected in 2019 have been any different than the Chinese ones.
We need to discuss this based on actual data, not some baseless guesses.