The COVID-19 pandemic may be the deadliest viral outbreak the world has seen in more than a century. But statistically, such extreme events aren’t as rare as we may think, asserts a new study.
Statistics are not for everyone, after all, they can be complicated, but by and large, the information collected also has its place in our understanding of past events as they relate to the present day and the future.
Researchers at Duke University looked at the historical record of epidemics from the year 1600 until now to estimate the probability of them recurring. The findings were published in the Proceedings of the National Academy of Sciences journal this week.
CTV News Canada is reporting that the researchers found the probability of a pandemic like COVID-19 recurring is about 2 percent in any given year. In other words, a person born in the year 2000 would have approximately a 38 percent chance of experiencing one by now.
And according to the authors, that probability is only growing, which highlights the need to adjust perceptions of pandemic risks and expectations for preparedness.
“The most important takeaway is that large pandemics like COVID-19 and the Spanish flu are relatively likely,” said William Pan, Ph.D., associate professor of global environmental health at Duke and one of the paper’s co-authors.
Understanding that pandemics aren’t so rare should raise the priority of efforts to prevent and control them in the future, he said.
Measuring the scale and frequency of disease outbreaks
The researchers used detailed modeling with a generalized Pareto distribution to analyze their data, finding out that the yearly number of epidemics is extremely variable, however, researchers also found patterns that allowed them to sketch out the probabilities of similar-scale events happening again, the study states.
“The slow decay of probability with epidemic intensity implies that extreme epidemics are relatively likely, a property previously undetected due to short observational records and stationary analysis methods,” the team writes in the paper.
Armed with this information, and using data from the Spanish flu pandemic, which is estimated to have killed more than 30 million people worldwide between 1918 and 1920, a similar event has a probability of between 0.3 and 1.9 percent of recurring within the next 400 years.
But we need to keep in mind that the probability of another outbreak of some kind of disease becoming a pandemic is growing, and fairly rapidly.
Based on the growing rate of novel pathogens such as SARS-CoV-2, swine flu, bird flu, Ebola, and many others having emerged in human populations in the past 50 years, the study estimates the probability of novel disease outbreaks will likely grow “three-fold” in the next few decades, according to Science Alert.
So with this increased risk factor in mind, the researchers estimate a pandemic similar in scale to COVID-19 is likely within a span of 59 years, a result they write is “much lower than intuitively expected.”
“Together with recent estimates of increasing rates of disease emergence from animal reservoirs associated with environmental change,” the team writes, “this finding suggests a high probability of observing pandemics similar to COVID-19 (probability of experiencing it in one’s lifetime currently about 38 percent), which may double in coming decades.”
“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,” Professor Pan says.
