Vinay Gupta was particularly worried about H5N1 back in 2008: http://guptaoption.com/6.SPRS.php http://guptaoption.com/6.SPRS.php https://archive.is/sCs8R htt

Vinay Gupta was particularly worried about H5N1 back in 2008: http://guptaoption.com/6.SPRS.php http://guptaoption.com/6.SPRS.php https://archive.is/sCs8R https://archive.is/sCs8R The tldr is that Spanish Flu had an extremely high case fatality rate (50–85%) in isolated communities that had no resistance to it, and that no human communities have any resistance to H5N1 (because it's never infected humans before.) So if it ever does make the jump and become significantly contagious, it could be very bad news — possibly as bad as "half the population of the planet dies" bad news.