A few facts about the H5N1 avian flu virus:
Humans who are in close contact with sick birds like poultry farmers and slaughterhouse workers are at a high risk of infection.... Despite confined examples of person-to-person transmission occurring since 1997, constant transmission has not been observed.
....H5N1 was first discovered in humans in 1997 in Hong Kong.... Worldwide, from 2003 to 05 October 2022, 865 cases were reported from 21 countries with a case fatality rate of 53%.
Virtually all cases of avian flu in humans have come from Egypt and Asia. In the entire rest of the world there have been 14 cases since 2003. The United States has had two of them: one in 2022 and one this year.
53% is a scary number. 10% would be a scary number. Hope if it mutates to better infect humans that it also mutates to kill us at a lower rate.
Relax! We're probably missing most cases, so the real death rate is much lower.
Be afraid! We're probably missing most cases, so it will be widespread before we notice.
So the CDC doesn't have much planning for a widespread disease with +2.5% kill rates because you can't actually plan for it. During covid we had fridge trucks and that was for 1%. 3% will basically result in collapse of the system.
That said there are different strains of bird flu. And it has to change so much to infect humans well its hard to say how deadly it would be. For example covid isn't that deadly if you are healthy but it evolved into the second most contagious disease known to man (right behind measles) so you had huge numbers getting sick in waves.