Two things -- the time index is set to 2:20 to skip THG's paid ad, and the 1872-73 flu outbreak was one of the bad, killer flu strains in the 19th century. This new vid got me wondering about it, as the cemetery out here in The Boonies got fattened up by it, including with family members from long before I was born.
That was very interesting. I checked some other sources and luckily only 1-2 percent of horses died but this outbreak brought the nation to a complete halt.