Children’s books authors have indeed responded to the dilemmas posed suddenly by Covid-19.
The IASC (Interagency Standing Committee) of W.H.O. hired a collaborative team to write “MyHero Is You: How Kids Can Fight Covid-19”. You can download the booklet free. There is a little more text than I recall seeing from the earliest grade school readers.
Of course, the writers are trying to manipulate kids into accepting sudden paradigm changes for behavior that seem bizarre even to adults. There is even the idea in some literature that heroes wear masks.
There is Elizabeth Verdick’s 2014 booklet ‘Germs Are Not for Sharing” (preview).
Of course, the bigger concept is that in nature, many more germs are beneficial and necessary (like in your intestinal tract) than harmful, and the beneficial bacterial compete with the dangerous ones. That is one more reason why the concept will seem so arbitrary and dictated by authority.
And then there is a "Germ Book" (video).
Pictures: from a boyhood train set, maybe around 1953. I just found this in the estate stuff so I used it.