How some cities ‘flattened the curve’ during the 1918 flu pandemic

A recent National Geographic Article offers us the opportunity to avoid such an outcome when it comes to pandemics. The Spanish Flu of 1918 was the last time the world felt biologic devastation similar to what we are now experiencing with Covid-19. US cities then chose to confront the epidemic utilizing non pharmacologic interventions, (NPI) in distinct ways, with significantly different outcomes. In National Geographic’s most recent publication, Strochli and Champine catalogue these different approaches, and illustrate how these varying approaches at the known onset of the disease, significantly impacted the degree of devastation that ensued.

Cities invoked various isolation techniques including social distancing and the closure of schools, churches and theaters. Those that delayed ordering social distancing measures and/or shortened isolation periods tended to have worse outcomes. The total death rates of Pittsburgh, Philadelphia, and New Orleans were examples of this approach. (see attached graphs)

Other cities, such as New York and St. Louis, chose to implement social isolation techniques earlier, with better outcomes. The difference in response rate between Philadelphia and St Louis (14 days) was associated with a death rate 50% lower in St Louis. Unfortunately, St Louis elected to relax isolation policies only 6 weeks into the city epidemic, leading to a resurgence of disease. Those cities that kept interventions in place did not experience this resurgence.

Sheila Fallon-Friedlander, MD commentary:

A key issue in evaluating overall effect of NPIs is the assessment of total excess death rates that occur with a disease, in addition to rate of increase in the epidemic curve and peak death rates. One can decrease the epidemic curve and peak death rates, but if social isolation is prematurely discontinued, a large proportion of the population will remain susceptible and a second wave of infection can be expected,and total excess death rates will likely rise. If an effective vaccine and treatment are not available, we must depend on social isolation or the development of herd immunity to protect the population; the latter is unlikely to develop at a sufficient rate (80-95%) within 6 weeks. Some say that herd immunity develop more slowly with social isolation in place, but the risk-benefit ratio favors utilizing social distancing despite this fact!

We must flatten the curve, so that peak death rates will decrease. In addition, spreading disease out over time will allow our over-stretched health care resources to “catch up” to increasing need. Though the time of financial suffering and infection may be prolonged, the overall outcome will be better. Prolonging isolation interventions will decrease overall disease, and hopefully give us time to discover optimal testing, therapies and vaccines. Identifying immune individuals through antibody testing may provide alternative means of freeing up a workforce that will be free of harm, while still isolating those that are susceptible. We must think about the economy, but at the same time protect the population.

Winston was right; let’s heed his call!