Another COVID-scale Pandemic in 59 Years ‘Statistically Likely’
A new study based on 400 years of historical records asserts that extreme pandemic events such as COVID are more common than believed.
The Duke University study, published in Proceedings of the National Academy of Sciences, used records of past outbreaks to estimate the intensity of those events and the yearly probability of them recurring.
It found the probability of a pandemic with similar impact to COVID is about 2% in any year, meaning that someone born in the year 2000 by now would have about a 38% chance of experiencing one. That probability is only increasing, highlighting the need to adjust perceptions of pandemic risks and expectations for preparedness, the researchers said.
“The most important takeaway is that large pandemics like COVID and the Spanish flu are relatively likely,” said study co-author William Pan, PhD, associate professor of global environmental health at Duke. The understanding that pandemics are not so rare should raise the priority of future prevention and control efforts, he said.
The study employed new statistical methods to measure the scale and frequency of disease outbreaks for which there was no immediate medical intervention over the past four centuries. Their analysis, including deadly pathogens including plague, smallpox, cholera, typhus and novel influenza viruses, found pandemics occurred with great variability in the past. But they also identified patterns that allowed them to describe the probabilities of similar-scale events happening again.
In the case of a pandemic like the Spanish flu, which killed more than 30 million people between 1918 and 1920, the probability of a pandemic of similar magnitude occurring ranged from 0.3% to 1.9% per year over the time period studied. Taken together, it is statistically likely that such a massive pandemic would occur within the next 400 years.
However, the data also show that the risk of intense outbreaks is increasing rapidly. Based on the increasing rate at which novel pathogens such as SARS-CoV-2 have broken loose in human populations in the past 50 years, the study estimates that the probability of novel disease outbreaks will likely triple in the next few decades.
With this increased risk factor, the researchers estimate that a COVID-scale pandemic is likely within a span of 59 years (by the year 2090), a result they write is “much lower than intuitively expected.” Although not included in the paper, they also calculated the probability of a pandemic capable of eliminating all human life, finding it statistically likely within the next 12 000 years.
That does not mean it will be 59 years before the next COVID-like pandemic, nor that the Spanish flu for another 300 years. Such events are equally probable in any year during the span, said Duke University Professor Gabriel Katul, another of the paper’s authors.
“When a 100-year flood occurs today, one may erroneously presume that one can afford to wait another 100 years before experiencing another such event. This impression is false. One can get another 100-year flood the next year,” explained Prof Katul.
Dr Pan noted that population growth, changes in food systems, environmental degradation and more frequent contact between humans and disease-harboring animals all may be significant factors for increasing frequency of pandemics. However, he stresses that the statistical techniques are not to explain the pandemics.
However, he hopes the study will spark deeper exploration of the factors that may be making devastating pandemics more likely – and how to counteract them.
“This points to the importance of early response to disease outbreaks and building capacity for pandemic surveillance at the local and global scales, as well as for setting a research agenda for understanding why large outbreaks are becoming more common,” Dr Pan said.
Source: Duke University
