What are the other health threats?
Influenza (all subtypes) is the big one, but there are also West Nile Virus, measles, various encephalitis viruses, Dengue, Chikungunya, malaria, etc. Take your pick.
Those are just the diseases that I pay attention to. There are many many other health threats out there, many of them infectious diseases, but also environmental threats, non-infectious diseases, and injuries.
A career in public health is job security.