I’ve slipped into the questionable habit of using “social distancing” and “lockdown” interchangeably. The latter is more politically charged and is perhaps best used to describe the more draconian forms of social distancing.
Dr. Markel had published a book, “When Germs Travel,” in 2004 that examined six major epidemics since 1900 and how they had traveled across the United States. He decided to work with Dr. Martin S. Cetron, the director of the C.D.C.’s quarantine division, to look more closely at the lessons of the Spanish flu of 1918.
The research started with St. Louis, which had moved relatively quickly to head off the spread of the flu, and Philadelphia, which waited much longer and suffered far more.
Officials in Philadelphia did not want to let the flu disrupt daily life, so they went ahead in September 1918 with a long planned paradethat drew hundreds of thousands of spectators to promote war bonds.
In St. Louis, by contrast, the city health commissioner quickly moved to close schools, churches, theaters, saloons, sporting events and other public gathering spots.
Dr. Markel and his team set out to confirm just how important a role timing had played in reducing deaths. They gathered census records and thousands of other documents detailing the date of the first infection, the first death, the first social distancing policies and how long they were left in place in 43 American cities.
Separately, Dr. Mecher and his team looked at the experience of 17 cities, using newspaper clips and other sources.
Both teams came to the same conclusion and published papers on their findings within months of each other in 2007. Early, aggressive action to limit social interaction using multiple measures like closing schools or shutting down public gatherings was vital to limiting the death toll, they found.
Steve Parker, M.D.