science

Yes, and I've heard people say "It'll be OK; the strain that goes pandemic won't be as lethal as the current strains." There's some truth in this, that extremely deadly viruses will tend to burn themselves out by killing their hosts so not spread so widely. So perhaps bird flu transmitted from person to person would not sustain the extremely high death rates this type of flu has shown in people in the past. But as the 1918 flu and even the COVID pandemic show, there's a lot of wiggle room for a virus between utterly deadly and utterly harmless, and even something that's far from the worst can still go pandemic and cause huge amounts of death, disruption and misery.