Kase doesn't have to worry about infecting Yamada, her bacteria doesn't work on plants!
For all we know, Yamada's some kind of herbal drug and Kase wasn't actually sick but going through some sort of withdrawl... Who knows how it works with humanoid plants?
Me thinks, sleepy Kase just had a nice dream of Yamada, which is why she woke up all cuddly ^^
Poor Fukami, getting the full blast of adorkable Kase that way...
Gotta love the various reactions to Kase having a fever.
Yamada: Oh, noes! I can't bother her now... I hope her pretty roommate takes good care of her... just not too good care...
Mikawacchi: Kase fell victim to something mundane as a cold!? Get out!
Inoue-senpai: MUAHAAHAHAA! A feeeeever from a lame coooold, such a whimp.
Kase's fangirls: Oh, noes! Our glorious goddess/future-husband is suffering! [let's go sacrifice a lamb]
Fukami: I'll try to help, but it's actually a nuisan-... whoops, she's actually kinda cute :3
Kase-san: I had a 39 degrees fever yesterday and today I have nothing better to do than to camp in front of my girlfriend's apartment until she gets home from work. Because I looooove her. [youtu.be/PpjOXxPka1s]