A competing hypothesis (this time I am specifically replying to Owain’s comment) is that it’s easier to catch infected travellers coming from the location where one expects them to come from. Asian countries certainly had it harder in phase 1 when the goal was to detect all the infections with Chinese travel history. However, as soon as even just one country in Europe failed at detection, the traveling dynamics changed and in phase 2 it subsequently became easier for the Asian countries, because they had basically zero incoming travel from Europe by that point. So while everyone was still focused on catching infections with Chinese travel history, Europeans were infecting other places in Europe, but less so places in Asia.
It’s maybe some supporting evidence that the Italy outbreak was connected to the early Germany outbreak, and that it only became clear that many countries were going to lose control of the situation once infected travellers had come from many different places. (At the same time, the Seattle outbreak is evidence against.)
Very hot countries have it easier to do contact-tracing. It’s plausible that the virus deactivates at 30 degrees Celsius (I think I may have read that in the often-cited Lipsitch article). In the hottest countries, public transport can be 30+ degrees and even grocery stores can be that warm. If infections happen primarily in indoor settings (e.g., business contacts or partying or household), contact tracing is easier, giving hot countries an initial advantage at preventing outbreaks early on. However, once contact tracing fails, that advantage shrinks. What remains is only that the r0 is lowered somewhat by heat interrupting certain types of of transmissions, but not all types. It wouldn’t surprise me therefore if hotter countries also need extreme measures to contain the case count from growing exponentionally, even if the doubling time might be generally lower for hot countries.
A competing hypothesis (this time I am specifically replying to Owain’s comment) is that it’s easier to catch infected travellers coming from the location where one expects them to come from. Asian countries certainly had it harder in phase 1 when the goal was to detect all the infections with Chinese travel history. However, as soon as even just one country in Europe failed at detection, the traveling dynamics changed and in phase 2 it subsequently became easier for the Asian countries, because they had basically zero incoming travel from Europe by that point. So while everyone was still focused on catching infections with Chinese travel history, Europeans were infecting other places in Europe, but less so places in Asia.
It’s maybe some supporting evidence that the Italy outbreak was connected to the early Germany outbreak, and that it only became clear that many countries were going to lose control of the situation once infected travellers had come from many different places. (At the same time, the Seattle outbreak is evidence against.)
Another hypothesis:
Very hot countries have it easier to do contact-tracing. It’s plausible that the virus deactivates at 30 degrees Celsius (I think I may have read that in the often-cited Lipsitch article). In the hottest countries, public transport can be 30+ degrees and even grocery stores can be that warm. If infections happen primarily in indoor settings (e.g., business contacts or partying or household), contact tracing is easier, giving hot countries an initial advantage at preventing outbreaks early on. However, once contact tracing fails, that advantage shrinks. What remains is only that the r0 is lowered somewhat by heat interrupting certain types of of transmissions, but not all types. It wouldn’t surprise me therefore if hotter countries also need extreme measures to contain the case count from growing exponentionally, even if the doubling time might be generally lower for hot countries.