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Tag: diseases

How do pandemics end? History suggests diseases fade but are almost never truly gone

<span class="caption">The COVID-19 new normal might be here for quite some time.</span> <span class="attribution"><a class="link rapid-noclick-resp" href="https://www.gettyimages.com/detail/photo/reflecting-on-her-day-royalty-free-image/1263884394" rel="nofollow noopener" target="_blank" data-ylk="slk:SolStock/E+ via Getty Images">SolStock/E+ via Getty Images</a></span>
The COVID-19 new normal might be here for quite some time. SolStock/E+ via Getty Images

When will the pandemic end? All these months in, with over 37 million COVID-19 cases and more than 1 million deaths globally, you may be wondering, with increasing exasperation, how long this will continue.

Since the beginning of the pandemic, epidemiologists and public health specialists have been using mathematical models to forecast the future in an effort to curb the coronvirus’s spread. But infectious disease modeling is tricky. Epidemiologists warn that “[m]odels are not crystal balls,” and even sophisticated versions, like those that combine forecasts or use machine learning, can’t necessarily reveal when the pandemic will end or how many people will die.

As a historian who studies disease and public health, I suggest that instead of looking forward for clues, you can look back to see what brought past outbreaks to a close – or didn’t.

people in line outside a COVID-19 testing site
people in line outside a COVID-19 testing site

Where we are now in the course of the pandemic

In the early days of the pandemic, many people hoped the coronavirus would simply fade away. Some argued that it would disappear on its own with the summer heat. Others claimed that herd immunity would kick in once enough people had been infected. But none of that has happened.

A combination of public health efforts to contain and mitigate the pandemic – from rigorous testing and contact tracing to social distancing and wearing masks – have been proven to help. Given that the virus has spread almost everywhere in the world, though, such measures alone can’t bring the pandemic to an end. All eyes are now turned to vaccine development, which is being pursued at unprecedented speed.

Yet experts tell us that even with a successful vaccine and effective treatment, COVID-19 may never go away. Even if the pandemic is curbed in one part of the world, it will likely continue in other places, causing infections elsewhere. And even if it is no longer an immediate pandemic-level threat, the coronavirus will likely become endemic – meaning slow, sustained transmission will persist. The coronavirus will continue to cause smaller outbreaks, much like seasonal flu.

The history of pandemics is full of such frustrating examples.

Once they emerge, diseases rarely leave

Whether bacterial, viral or parasitic, virtually every disease pathogen that has affected people over the last several thousand years is still with us, because it is nearly impossible to fully eradicate them.

The only disease that has been eradicated through vaccination is smallpox. Mass vaccination campaigns led by the World Health Organization in the 1960s and 1970s were successful, and in 1980, smallpox was declared the first – and still, the only – human disease to be fully eradicated.

Children holding smallpox vaccination certificates
Children holding smallpox vaccination certificates

So success stories like smallpox are exceptional. It is rather the rule that diseases come to stay.

Take, for example, pathogens like malaria. Transmitted via parasite, it’s almost as old as humanity and still exacts