My guess is that it is probably acting like a hybrid flu and killing the young and strong. Those are the bugs that scare the CDC.
The normal human flu kills people with weak immune systems, the very young and very old, often by secondary pneumonia.
Hybrid flu kills healthy adults in their prime by cytokine storm and can do it in a hurry. Hybrid flus are a cross between an animal flu and a human flu. This virus is said to also have an animal origin. That’s what makes your immune system go berserk.
Expert opinion is that those deaths were preventable
However, healthcare providers, medical experts, and published data from the 1918 period suggest that most deaths were caused by secondary bacterial pneumonias
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2600384/