The bed bug connection to smallpox was discovered in the late 1920s. It was recognized as the reason that those caring for family members with the pox at home were not getting infected at the high rate that nursing staff and patients in hospitals were.
And yeah, if you get the impression I sound a little spooked by the thing, I am. My undergraduate study was pathogenic microbiology. I've handled pathogenic bacteria a fair amount but you don't touch anything like this outside a Class 4 containment facility, it's that nasty.