The deadliest pandemic in modern history, known as the Spanish flu or the 1918 flu pandemic, contains crucial data that may guide us amid the current outbreak of COVID-19. In the absence of a vaccine, interventions such as social distancing, stay-at-home mandates and travel restrictions are not novel ideas. Based on historical data, we now know that the timing and duration of these interventions are key in order to “flatten the curve” of infections.
Flattening the Curve
Since the first known case of the flu surged in the United States, the virus began to spread quickly across largely populated cities. St. Louis banned public gatherings and instituted social distancing and self-quarantine shortly after two days. These early interventions are what kept the city at the lowest death rate and relieved pressure on the healthcare system. On the other hand, Philadelphia encountered the highest spike of death rates then decided to implement drastic measures after eight days. As a result, the death rate in Philadelphia was more than half of the rate in St. Louis.
Those cities that ordered social distancing later and for a shorten period of time, underwent the highest overall deaths; while cities that responded sooner and for longer periods of time, experienced the lowest death rate by flattening the curve. In addition, lifting preventative measures too early caused the city of St. Louis to relapse and trend into a second wave. Extending interventions for a prolonged period of time may help prevent a setback.
This data suggest early and efficient preventative measures, substantially lowered the death rate by approximately 50% and reduced transmission by 30-50% compared to those interventions that were introduced later or lifted too early. While the current outbreak of COVID-19 sets us in uncharted territory, there is a lot to learn from our past a century later.
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References:
https://www.pnas.org/content/104/18/7588.abstract
