Yes, certainly, an antagonist can be a disease. A great example is the titular antagonist in The Andromeda Strain by Michael Crichton.
Medicine tha prevents disease is called vaccine as it creates immunity in your body. Curruently there are no medicines that "cure" the disease but it helps your immune system gain immunity. But, antibiotics do kill bacteria that cause disease so it can be seen as "curing" the disease.
antagonist
If antagonist did not want to harm protagonist, he wouldn't be antagonist. His opposition to protagonist is what makes him antagonist.
Antagonist or villain.
who is the antagonist in sounder
Cory is the antagonist.
Bryce is the antagonist.
Antagonist
The main charachter is usually reffered to as the protagonist(or the good guy) and the person that he/she conflicts with is usually refered to as the antagonist(or the bad guy).
A character who is opposed or competes the main character. * is called the antagonist while the main character is called the protagonist,
Antinous is an antagonist.
curley is the antagonist