So far what I have noticed is people getting infected have another common factor………they were not vaccinated with the Small Pox vaccine.as that ended in the early 70s.
My pediatrician insisted on getting my brother and me vaccinated against Smallpox before the vaccine was withdrawn. We got vaccinated before 1972 when we switched doctors for other reasons.
It's probably difficult to find many people younger than 55 years old today who got a routine childhood Smallpox vaccination. The issue I see is that even promiscuous people tend to decrease the numbers of sexual partners by the time they get into their fifties.
You hit the nail. Good comment. Thanks.