Endemic seasonal influenza didn't just recently acquire the ability to jump to humans. Even considering the 2009 H1N1 pandemic the H1 protein is descended from

Endemic seasonal influenza didn't just recently acquire the ability to jump to humans. Even considering the 2009 H1N1 pandemic the H1 protein is descended from the human strain which circulated in 1918-1957 and there was still enough immunity in the human race in 2009 to make that virus not that novel. This monkeypox virus is brand new to the human immune system.