As the coronavirus continues to spread around the world, officials are studying the quickest and most effective way to contain its spread. With experts saying a vaccine is least 18 months away and no definitive cures or preventatives, the most effective seems to be avoiding social contact as much as possible, or “social distancing”. But does it work? For data we go back to a previous epidemic that swept across the nation, the 1918 Spanish flu. Among the hardest hit cities was Philadelphia, where the infection rate skyrocketed after a huge parade attended by 200,000 Philadelphians was allowed by the Mayor and Health Commissioner to occur even though the flu had already started to take hold in the city. Immediately afterward, the city’s health care system was overrun, and the sick and dying were left with no place to get treatment. However, the city of St. Louis practiced immediate and extreme social distancing, closing schools, movie theaters, sporting events, and public gatherings just 2 days after the flu hit that city. The result was that the flu spread much more slowly throughout St. Louis than in Philadelphia, and that saved thousands of lives. The point of social distancing is to infect all those who are destined to be infected much more slowly, instead of all at once. This saves lives by avoiding overrunning hospital capacity. When a deluge of sick patients present themselves to hospitals all at once, many of the sick can’t be treated and are left to die at home and in the streets. Philadelphia experienced a multiple of the death rate of St. Louis simply because in St. Louis all the sick that needed hospitalization were able to be absorbed by the health care system and treated, albeit over a longer period of time. Dr. Max Starkloff, St. Louis’ Health Commissioner, is still remembered there for his strong will and tremendous foresight. Chart from Scott Sievert (stsievert.com).