Preventing the spread of infection

My Marksman recently got the Infect spellbook, and I tried it out on a battle with some melee Orcs. It ended up spreading to their entire team, then one of the Orcs ran over to us, and infected my entire team! I was under the impression it only spreads on the turn that it was cast.
This is obviously a problem, since making everyone (including my team) diseased isn't particularly useful.
Is Infect really only useful against enemies that are exclusively range-based? Is there a way to prevent it from spreading to my team, besides only using it against non-melee enemies, and avoiding melee attacks while they're infected?
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Quick Answer about "Preventing the spread of infection"
What are 3 ways to prevent infection?
Good hygiene: the primary way to prevent infectionsWhat is the #1 method to prevent spread of infection?
Take action and practice hand hygiene often. Use soap and water or an alcoholbased hand rub to clean your hands. It only takes 15 seconds to practice hand hygiene.2 Preventing the spread of infection
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