Disease clinics aren't curing zombie spores
(kudos to Luma plays for pointing this out)
The enclosed sav file is using dev mode and sandbox active to test it.
The screen shots show there is illness present in the duplicants, the disease clinic has serums, and the errand bar doesn't recognise the presences of zombie spores.
Infect a duplicant with zombie spore, give disease clinic serum vials and power while skilling up relevent duplicants.
Check the disease clinic's errand task and it will say "no treatable illness"