I asked how old she was when this happened, and she said she was really young - obviously still in a crib - and that she thinks it's her earliest memory.
It was probably around 1961, assuming my mother was around 2. A vaccine for rubella (German measles) wouldn't come out until 1969. My grandfather was not exactly a modern man, in the sense of doing much of the care-giving work of parenting. My first instinct was an "Awww . . ." at the thought of my tough-as-nails grandfather being so concerned about his sick toddler that he'd sleep on the floor. But then I remembered something about rubella; it's not typically very dangerous for the kids who have it; it's dangerous for pregnant women and their unborn babies. According to the CDC,
Rubella is a contagious disease caused by a virus. Most people who get rubella usually have a mild illness, with symptoms that can include a low-grade fever, sore throat, and a rash that starts on the face and spreads to the rest of the body. Rubella can cause a miscarriage or serious birth defects in an developing baby if a woman is infected while she is pregnant.
Grandpa was sleeping on the floor because Grandma couldn't. She was likely either pregnant with my uncle, or was keeping away out of an abundance of caution in case she was pregnant. Perhaps limiting contact with women of child-bearing age was just a general recommendation for kids with German measles.
That was 1961.
This is 2016. Old-fashioned men like my grandfather are a vanishing breed. Rubella is a vanishing disease. Men sleeping on the floor next to their toddlers' crib provoke fewer "Awwws" and more "You're Doing It Wrongs." Even pregnant mothers don't have to worry about getting rubella from their sick kids, when both mother and child have been vaccinated against it.
The moment has passed.