I mean, in the past they might not have known that. And in the following chapter, they do discover it is in fact caused by malnutrition, so...
Maybe give it a chance? ╮(￣▽￣)╭
Oh, they do recognize that it's not infectious? I guess I should've kept reading. My fault for giving up on the author instead of trusting that they were just repeating historical false information D:
If you read back, the story is that it's got a lot of misinformation surrounding it. The sick brother is the one who knows what he's talking about because he continued his father's research into it. Or did he say it's contagious?
Either way, I think the implication here is that it's still early in understanding it in this world.
I don't know if it's just a translation error, but scurvy is not a contagious disease it's a personal disease caused by undernutrition .. I really can't take this part seriously