This graph could save your life!


George Santayana’s most famous quote is used so often that it has become a cliche:

Those who do not remember the past are condemned to repeat it.

It’s just as true in epidemiology as it is in history. That’s why this graph may save your life.

Beware the second wave!

It’s a graph of the US death rate during the Spanish Flu epidemic of 1918-1919. It illustrates what happens when you stop social distancing and open up the economy too soon.

Like many pandemics, the disease and death of the Spanish flu pandemic did not occur all at once. It happened in three distinct waves.

Back in 1918 there were no medical or pharmacological tools to mitigate the severity of the disease; there were no anti-virals and no vaccines for influenza. Public health officials had only natural methods at their disposal: they implemented social distancing to reduce the spread of the disease and the number of deaths.

And it mostly worked.

Most of the social distancing measures used today were well known and implemented with mixed severity and mixed outcomes in 1918. Total isolation, if implemented early, is effective…

The effectiveness of social distancing … is considered to depend on how well and how soon it implemented. In 1918, St Louis implemented these early and well, but Philadelphia did not, including allowing a WWI parade. Philadelphia had a greater rate of infection. However, when St Louis later started cutting back on social distancing restrictions, influenza cases spiked, and the city had to reinstate the measures.

But people chafed at the restrictions and suffered from the resulting economic devastation. Cases and deaths were dropping and politicians were declaring that the worst was over. Sound familiar?

There was tremendous political pressure to lift the restrictions. At first the predictions of the protesters seemed to be confirmed. Cases of the flu continued to drop and it nearly disappeared during the summer months. But it hadn’t been eliminated because social distancing measures were ended too soon. In the fall, it came roaring back.

Lifting control measures when a population is still in the exponential part of the curve, and before any external factors that can limit a wave take effect (eg, a vaccine or antiviral), allows that population to regress to the point before controls were implemented. However, by that time, a much higher number of individuals will be infected. If doubling time reaches 3 days early in the wave, 10 infected persons will increase to 20 in 3 days. If the doubling time when controls are lifted is still 3 days, but the number of infected persons is 1000, then the number will go from 1000 to 2000 infected persons in 3 days, and then to 4000 in another 3 days.

This is especially true when, as in the case of COVID-19, the virus can spread asymptomatically. Moreover, the virus can continue to mutate as it spreads, possibly becoming more virulent.

When the Spanish flu returned in the fall, cases and death rates exploded. Ultimately 675,000 American died of the flu and — as the graph demonstrates — the majority of deaths occurred in the second wave.

There are a lot of reasons to believe that COVID-19 may behave like the Spanish flu and similar pandemics. Indeed, nearly every prediction made by doctors and scientists about the COVID-19 pandemic has come to pass; those predictions were based directly on the Spanish flu experience. That means that the worst of this pandemic still lies ahead.

Where are we now? I added the green arrow to the graph to show that we appear to be cresting the first wave. It seems to those who are protesting the restrictions that there is no reason to continue them. That’s what those who protested the 1918 restrictions thought, too.

They were dead wrong! For every person who died in the first wave of the Spanish flu, up to 10 died in the second and third waves. That means that if 60,000 Americans have died thus far, we can expect as many as 600,000 more to die in the coming 12-18 months if we lift restrictions prematurely.

That doesn’t have to happen. We can keep restrictions in place, only gradually easing them to be sure that the disease does not come roaring back. If the graph convinces politicians to move slowly, hundreds of thousands of lives (including YOURS!) may be saved. Even if politicians choose to behave irresponsibly, you can still heed the lessons of the graph and keep practicing social distancing as far as you are able, continuing to wear masks and avoiding large gatherings of people as much as you can.

Those who refuse to learn from the past are condemned to repeat it. Just because the protesters are determined to ignore the lessons of 1918 and kill themselves, their relatives and their friends doesn’t mean the rest of us have to follow them into the abyss.

Remember this graph; it could save your life and the lives of those you love.