They tended to bury those who died of disease in mass graves right into the 20th century- because so many people died at once and without vaccines handling bodies wasn’t smart. Like the mass grave of the (possibly exaggerated) 300 Russian Mennonites from 1875 in Florence USA.
In the U.K. it was common practice to bury babies in mass graves up until the 1960’s or 70’s under medical circumstances or where private funds for burial weren’t available. There’s other instances of mass and unmarked graves for babies and especially any age of victim of transmittable illness- and a great deal of the time burning of bodies for those with communicable disease was used because- derp. Without cures or vaccines you didn’t want to keep plague bodies around nor did you want them where creatures could climb and feast in them and then become a disease vector to infect more people.
Or.... something something, vaccines bad, conspiracy conspiracy, crazy talk, flat earth, fake moon landing, tin foil hats, I swear I know a friend of a friends sisters yoga class mate who’s aunt was a healthy 21 year old and tried vaccines once and died of autism.
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(I'm sorry if this offends anyone)