That always seemed odd to me. I mean, measles?
When I was a lad , I had measles. My sister had measles. Everyone I knew had measles. It was universal. Nobody ever died of it, or even got seriously sick.
We didn't have any medical treatment, or even a doctor. Just the usual sick child stuff, bed rest, soup, cod liver oil, whatever else the Grandmothers' Family Physician book recommended. Same as everybody, same as our parents and grandparents before us.
The young child, maybe I guess. But two healthy adults?
I know some sources say smallpox, which makes the outcome more understandable, but deepens the mystery. After all mealses and smallpox are two diseases that contemporary physicians knew very well indeed. and they are not really all that confusable. It's hard to see them getting the diagnosis that wrong. And smallpox wasn't shameful, there would be no reason to try to cover it up.