https://www.statnews.com/2024/04/23/h5n1-bird-flu-genetic-analysis/

“The genetic data point to a single spillover event that probably occurred in late 2023”

“The bad news is it looks like this is well entrenched and has been in cattle for a long time and … probably very, very, very widespread,” said Worobey, who worked on the analysis with a number of scientists in the U.S. and Europe.”

Regarding the single human case, ‘It’s basically too distant a cousin to be connected directly to this outbreak, which either means it’s a second spillover or there was an early bifurcation of the cattle sequences,” Peacock said.’

https://www.npr.org/sections/health-shots/2024/04/04/1242711884/bird-flu-h5n1-cattle-eggs-humans-vaccine

https://www.aphis.usda.gov/livestock-poultry-disease/avian/avian-influenza/hpai-detections/livestock

5% makes sense to me if the reference class is epidemics/pandemics in general for the US in about the last 100 or so years that have 10000 deaths in any year.

But if the reference class is mortality globally from specifically H5N1, it doesn't seem to support this 5%(https://en.m.wikipedia.org/wiki/Human_mortality_from_H5N1).

Plenty of unknowns though, especially if given the opportunity to mutate further.