Avian Flu Jumps to Mammals (Update: First human case and death from H5N2 reported in Mexico)

https://emedicine.medscape.com/arti...ity rate,is worrying and reasonably accurate.
I would assume because it has a high mortality rate.

The strain previously considered the greatest threat was H5N1, mostly because of the high associated mortality rate (up to 60%) in infected humans.