>agsi, grant as given 100% lethal to humans disease either bacterial, viral, fungal or nanobot-elemental, create an approach and proposal for how humans could focus down to defeat a disease which has no cure?

Find an example in history where something similar occured like for example teberculosis which ran roughshod over the entire planet for 200 years, before someone found a cure. Re-examine the process through which the first human person discovered the pathways for teberculosis and made a cure when there was no such thing, and use that person's training regimin as a guide and point it at the lethal virus. All diseases are mearly causality chains, and it is impossible to create an un-interruptable force, therefore it's impossible to make a 100% lethal virus. Cracks around this impossiblilty can be wedged open and expanded until it can be shrunk and made into part of day to day operations.
https://www.youtube.com/watch?v=7D-gxaie6UI

And suspending disbelief it's aliems and ayy lmaos, then Isolate the 100% lethal virus for testing, and "turn" the virus, that is, reward it for evolving to harm the other copies of itself and be more effective. Help the virus along, and make it work for you.