It was a random conversation among strangers who met by chance one day in a Victoria-area park.
One person remarked offhandedly that COVID-19 is giving us practice in dealing with pandemics and widespread deadly epidemics, “because we’ll probably see more epidemics and pandemics.”
“No. Pandemics happen once every 100 years.” The response was adamant.
A third person spoke. “I don’t know about that.”
“No. History shows worldwide pandemics happen only once a century.” He listed some examples.
“But the world has changed drastically this past century. The conditions that enabled COVID to emerge, spread around the world and mutate still exist. That would suggest the odds of pandemics occurring more frequently are greater.”
Whether vaccinated, anti-vax or anti-vaccine passport, none of us wants to go through what we’ve experienced these past two years again. We all look forward to putting COVID-19 behind us.
But the conversation in the park raises an unwelcome spectre. Is COVID-19 the only pandemic we’ll experience?
Not surprisingly, a great many pointy-headed people have been looking into this. In fact, they’ve been considering questions like this since 2003, when SARS showed the world how vulnerable we are to newly emerging, highly infectious and deadly diseases.
A recent paper published in the Proceedings of the National Academy of Sciences indicates concern might be warranted. The paper suggests that extreme events such as the COVID-19 pandemic may not be as rare as we think.
The conclusions are based on a statistical analysis of new information about novel disease outbreaks that have occurred over the past 400 years. The U.S. and Italian research team measured the scale and frequency of 476 disease outbreaks since 1600 — back when Galileo, Shakespeare and Samuel de Champlain lived — and for which no medical intervention was available at the time. This includes plague, smallpox, cholera, typhus and novel influenza viruses. Currently active infectious diseases were excluded — for example, COVID-19, HIV, Ebola and malaria.
The analysis revealed considerable variability in the rate at which past pandemics have occurred. For extreme pandemics such as the Spanish flu, which killed more than 50 million people around the world in 1918-1920 and is modern history’s deadliest pandemic, the probability of a pandemic of similar magnitude occurring ranged from somewhere between 0.3 and 1.9 per cent each year over the past four centuries. Taken another way, it is statistically likely that a pandemic of such extreme scale will occur within the next 400 years.
However, a pandemic with an impact level similar to that of COVID-19 has about a two per cent probability of occurring each year. For those of us who aren’t statisticians, that means that when you add that probability up across an entire lifetime, we each have a 38 per cent chance of experiencing a major pandemic at least once in our lives.
Worse yet, the odds of that happening are growing. Based on the increasing rate at which novel pathogens like the COVID-19 virus have broken out in human populations over the past five decades, the researchers say the probability of novel disease outbreaks will likely increase threefold in the coming decades.
That is, another pandemic similar in scale to COVID-19 is likely within 59 years. Again, we’re talking statistics — just as a once-in-300-year earthquake can happen a year or 400 years later, a once-in-60-year pandemic could also happen again anytime.
Other studies have shown that factors such as global population growth, climate change, environmental degradation, changes in food systems, increased contact between humans, livestock and disease-harbouring animals, and the prevalence, incidence and speed of international travel combine to drive the emergence and spread of epidemics. These conditions enabled COVID-19 to spread quickly, mutate, and spread again. These conditions aren’t going away soon.
“The most important takeaway is that large pandemics like COVID-19 and the Spanish flu are relatively likely,” said William Pan, one of the paper’s co-authors and a global environmental health researcher at Duke University. Understanding that pandemics aren’t particularly rare should prompt us to prioritize our efforts to prevent and control them in the future.