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How do pandemics end? History suggests diseases fade but are almost never truly gone
Instead of looking forward, we should be consulting the past.
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.
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.
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 a heavy disease burden today: There were about 228 million malaria cases and 405,000 deaths worldwide in 2018. Since 1955, global programs to eradicate malaria, assisted by the use of DDT and chloroquine, brought some success, but the disease is still endemic in many countries of the Global South.
Add to this mix relatively younger pathogens, such as HIV and Ebola virus, along with influenza and coronaviruses including SARS, MERS and SARS-CoV-2 that causes COVID-19, and the overall epidemiological picture becomes clear. Research on the global burden of disease finds that annual mortality caused by infectious diseases – most of which occurs in the developing world – is nearly one-third of all deaths globally.
Today, in an age of global air travel, climate change and ecological disturbances, we are constantly exposed to the threat of emerging infectious diseases while continuing to suffer from much older diseases that remain alive and well.
Once added to the repertoire of pathogens that affect human societies, most infectious diseases are here to stay.
Plague caused past pandemics – and still pops up
Even infections that now have effective vaccines and treatments continue to take lives. Perhaps no disease can help illustrate this point better than plague, the single most deadly infectious disease in human history. Its name continues to be synonymous with horror even today.
Plague is caused by the bacterium Yersinia pestis. There have been countless local outbreaks and at least three documented plague pandemics over the last 5,000 years, killing hundreds of millions of people. The most notorious of all pandemics was the Black Death of the mid-14th century.
Yet the Black Death was far from being an isolated outburst. Plague returned every decade or even more frequently, each time hitting already weakened societies and taking its toll during at least six centuries. Even before the sanitary revolution of the 19th century, each outbreak gradually died down over the course of months and sometimes years as a result of changes in temperature, humidity and the availability of hosts, vectors and a sufficient number of susceptible individuals.
Some societies recovered relatively quickly from their losses caused by the Black Death. Others never did. For example, medieval Egypt could not fully recover from the lingering effects of the pandemic, which particularly devastated its agricultural sector. The cumulative effects of declining populations became impossible to recoup. It led to the gradual decline of the Mamluk Sultanate and its conquest by the Ottomans within less than two centuries.
That very same state-wrecking plague bacterium remains with us even today, a reminder of the very long persistence and resilience of pathogens.
Hopefully COVID-19 will not persist for millennia. But until there's a successful vaccine, and likely even after, no one is safe. Politics here are crucial: When vaccination programs are weakened, infections can come roaring back. Just look at measles and polio, which resurge as soon as vaccination efforts falter.
Given such historical and contemporary precedents, humanity can only hope that the coronavirus that causes COVID-19 will prove to be a tractable and eradicable pathogen. But the history of pandemics teaches us to expect otherwise.
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What is human dignity? Here's a primer, told through 200 years of great essays, lectures, and novels.
- Human dignity means that each of our lives have an unimpeachable value simply because we are human, and therefore we are deserving of a baseline level of respect.
- That baseline requires more than the absence of violence, discrimination, and authoritarianism. It means giving individuals the freedom to pursue their own happiness and purpose.
- We look at incredible writings from the last 200 years that illustrate the push for human dignity in regards to slavery, equality, communism, free speech and education.
The inherent worth of all human beings<p>Human dignity is the inherent worth of each individual human being. Recognizing human dignity means respecting human beings' special value—value that sets us apart from other animals; value that is intrinsic and cannot be lost.</p> <p>Liberalism—the broad political philosophy that organizes society around liberty, justice, and equality—is rooted in the idea of human dignity. Liberalism assumes each of our lives, plans, and preferences have some unimpeachable value, not because of any objective evaluation or contribution to a greater good, but simply because they belong to a human being. We are human, and therefore deserving of a baseline level of respect. </p> <p>Because so many of us take human dignity for granted—just a fact of our humanness—it's usually only when someone's dignity is ignored or violated that we feel compelled to talk about it. </p> <p>But human dignity means more than the absence of violence, discrimination, and authoritarianism. It means giving individuals the freedom to pursue their own happiness and purpose—a freedom that can be hampered by restrictive social institutions or the tyranny of the majority. The liberal ideal of the good society is not just peaceful but also pluralistic: It is a society in which we respect others' right to think and live differently than we do.</p>
From the 19th century to today<p>With <a href="https://books.google.com/ngrams/graph?year_start=1800&year_end=2019&content=human+dignity&corpus=26&smoothing=3&direct_url=t1%3B%2Chuman%20dignity%3B%2Cc0" target="_blank" rel="noopener noreferrer">Google Books Ngram Viewer</a>, we can chart mentions of human dignity from 1800-2019.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDg0ODU0My9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1MTUwMzE4MX0.bu0D_0uQuyNLyJjfRESNhu7twkJ5nxu8pQtfa1w3hZs/img.png?width=980" id="7ef38" class="rm-shortcode" data-rm-shortcode-id="9974c7bef3812fcb36858f325889e3c6" data-rm-shortcode-name="rebelmouse-image" />
American novelist, writer, playwright, poet, essayist and civil rights activist James Baldwin at his home in Saint-Paul-de-Vence, southern France, on November 6, 1979.
Credit: Ralph Gatti/AFP via Getty Images
The future of dignity<p>Around the world, people are still working toward the full and equal recognition of human dignity. Every year, new speeches and writings help us understand what dignity is—not only what it looks like when dignity is violated but also what it looks like when dignity is honored. In his posthumous essay, Congressman Lewis wrote, "When historians pick up their pens to write the story of the 21st century, let them say that it was your generation who laid down the heavy burdens of hate at last and that peace finally triumphed over violence, aggression and war."</p> <p>The more we talk about human dignity, the better we understand it. And the sooner we can make progress toward a shared vision of peace, freedom, and mutual respect for all. </p>
With just a few strategical tweaks, the Nazis could have won one of World War II's most decisive battles.
- The Battle of Britain is widely recognized as one of the most significant battles that occurred during World War II. It marked the first major victory of the Allied forces and shifted the tide of the war.
- Historians, however, have long debated the deciding factor in the British victory and German defeat.
- A new mathematical model took into account numerous alternative tactics that the German's could have made and found that just two tweaks stood between them and victory over Britain.
Two strategic blunders<p>Now, historians and mathematicians from York St. John University have collaborated to produce <a href="http://www-users.york.ac.uk/~nm15/bootstrapBoB%20AAMS.docx" target="_blank">a statistical model (docx download)</a> capable of calculating what the likely outcomes of the Battle of Britain would have been had the circumstances been different. </p><p>Would the German war effort have fared better had they not bombed Britain at all? What if Hitler had begun his bombing campaign earlier, even by just a few weeks? What if they had focused their targets on RAF airfields for the entire course of the battle? Using a statistical technique called weighted bootstrapping, the researchers studied these and other alternatives.</p><p>"The weighted bootstrap technique allowed us to model alternative campaigns in which the Luftwaffe prolongs or contracts the different phases of the battle and varies its targets," said co-author Dr. Jaime Wood in a <a href="https://www.york.ac.uk/news-and-events/news/2020/research/mathematicians-battle-britain-what-if-scenarios/" target="_blank">statement</a>. Based on the different strategic decisions that the German forces could have made, the researchers' model enabled them to predict the likelihood that the events of a given day of fighting would or would not occur.</p><p>"The Luftwaffe would only have been able to make the necessary bases in France available to launch an air attack on Britain in June at the earliest, so our alternative campaign brings forward the air campaign by three weeks," continued Wood. "We tested the impact of this and the other counterfactuals by varying the probabilities with which we choose individual days."</p><p>Ultimately, two strategic tweaks shifted the odds significantly towards the Germans' favor. Had the German forces started their campaign earlier in the year and had they consistently targeted RAF airfields, an Allied victory would have been extremely unlikely.</p><p>Say the odds of a British victory in the real-world Battle of Britain stood at 50-50 (there's no real way of knowing what the actual odds are, so we'll just have to select an arbitrary figure). If this were the case, changing the start date of the campaign and focusing only on airfields would have reduced British chances at victory to just 10 percent. Even if a British victory stood at 98 percent, these changes would have cut them down to just 34 percent.</p>
A tool for understanding history<p>This technique, said co-author Niall Mackay, "demonstrates just how finely-balanced the outcomes of some of the biggest moments of history were. Even when we use the actual days' events of the battle, make a small change of timing or emphasis to the arrangement of those days and things might have turned out very differently."</p><p>The researchers also claimed that their technique could be applied to other uncertain historical events. "Weighted bootstrapping can provide a natural and intuitive tool for historians to investigate unrealized possibilities, informing historical controversies and debates," said Mackay.</p><p>Using this technique, researchers can evaluate other what-ifs and gain insight into how differently influential events could have turned out if only the slightest things had changed. For now, at least, we can all be thankful that Hitler underestimated Britain's grit.</p>
We’ve mapped a million previously undiscovered galaxies beyond the Milky Way. Take the virtual tour here.
See the most detailed survey of the southern sky ever carried out using radio waves.
Astronomers have mapped about a million previously undiscovered galaxies beyond the Milky Way, in the most detailed survey of the southern sky ever carried out using radio waves.
A new study shows our planet is much closer to the supermassive black hole at the galaxy's center than previously estimated.
Credit: NAOJ<p><em>Arrows on this map show position and velocity data for the 224 objects utilized to model the Milky Way Galaxy. The solid black lines point to the positions of the spiral arms of the Galaxy. Colors reflect groups of objects that are part of the same arm, while the background is a simulation image.</em></p>
Apple sold its first iPod in 2001, and six years later it introduced the iPhone, which ushered in a new era of personal technology.