On page 320 of Huck Finn, what does this line mean?

Question

"...a stranger don't come every year, and so he lays over the yaller fever, for interest, when he does come."

Answer 1

I actually don't know the context, but it sounds as if they're saying that a stranger doesn't come around very often, but when they do, they leave a sort of memento... in this case the yellow fever...? I was thinking of interest as more of a payment over time thing

Answer 2

I believe it means that since strangers don't come around very often, they're more interesting than yellow fever when they do come. Without the rest of the sentence (I don't have a book here, and I probably wouldn't have the same edition you do anyway), that's the best I can do.