@skigeorgia77 @Bob_Wachter CDC delta briefing, you can download it from here. They cite some studies there, but I'm pretty sure there have since been additional studies confirming.
https://www.washingtonpost.com...
@Skigorgia77@Bob_Wachter CDC delta简报，您可以从这里下载。他们引用了一些研究，但我敢肯定，此后有更多的研究证实了这一点。
https://www.washingtonpost.com...