We have had Malaria for decades, and it is still not controlled. Then we had Smallpox and Polio, which were dealt with. Flu? However, we also have Dengue, Ebola, Marburg, SARS, MERS and Covid, and we know that they can all pass from mammals to humans to humans. They do kill.
The latest is the H5N1 virus (Bird Flu) and it has been found in cow's milk in the US, the stuff we all drink. It is also in foxes, seals, mink and dolphins in the UK. We culled millions of poultry and other mammals to try to contain it. It is now known that it can pass to humans via many routes. So far it has only been seen by contact, simple contact (sweat) and not just with bodily fluids such a urine, faeces and blood, but if it becomes airborne, the way bubonic plague turned into pneumonic plague, all bets are off.
The threat is driven by a few things: too many of us; our concentration in mega cities; the ways we can travel from place to place, and very quickly; our increasing closeness to what were once animals we contacted rarely.
When it comes to bacteria we are fighting a losing battle - a simple cut to a finger could kill.
Never mind, we can all sit in our our windmill driven free electricity net-zero air pump houses or aircon EVs and we'll all be safe.