There are parasites and diseases that are nearly removed from human experience.
Contagions like polio were prevalent and often fatal. There are living survivors of polio in this world. It could go away forever. If humans could cooperate enough to focus on the last areas of infection.
Humans could work together for a select few sicknesses.
There are parasites and diseases that would be much harder to remove. Things that have more than humans in mind.
The ring worm parasite is one example. Even if no human was infected by ringworm, it would be possible to have enter your body.
There is a parasite called Toxoplasmosis that has a complex lifecycle. Felines and mammals become infected, but the parasite only breeds when an infected feline eats an infected mammal.
Which is the best way to eliminate that parasite from the human population? Quarantine humans from cats? Quarantine cats cared for by humans from infected areas?
A reduction of diseases and parasites from the human experience is good goal.
Do we really know enough about these things? Where is that tradeoff point?
Sometimes a parasite is also a symbiote. Doing good, in unexpected ways.
How heavy handed should we humans be? Do we harm other humans in trying to eliminate diseases?
Maybe the best thing is to channel a cooperative urge. Before we band together in a crowd.. Before we say 'those people are a menace, because they are sick'..
Maybe we ought to work hard as humanity. Work hard to have sensible compassion. People have been marginalized harshly for simply getting sick (of just thought to be sick).
Quarantine techniques can be effective. Quarantining in way that does not punish the sick is not easy.