Large pandemics like COVID-19 are statistically more likely than originally thought, study suggest

TORONTO -

Large pandemics like COVID-19 are statistically more likely than originally thought, a new study suggests.

The study, entitled “Intensity and frequency of extreme novel epidemics” was published in the Proceedings of the National Academy of Sciences journal this week by researchers at Duke University, and analyzed novel disease outbreaks over the past 400 years to estimate the intensity of the events and the yearly probability of them recurring, according to a press release.

Researchers found that the probability of a pandemic with similar impact of COVID-19 is about two per cent in any given year – meaning that a person born in the year 2000 had approximately a 38 per cent chance of experiencing one by now.

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The study states that that pandemic probability is also increasing, which researchers say highlights the need for an adjustment in 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 study co-author William Pan in the release, adding that understanding that pandemics are not so rare should raise preventative efforts.

To compile the data needed for the study, researchers – in tandem with the University of Padua in Italy, used new statistical methods to measure the scale and frequency of disease outbreaks which had no immediate medical intervention over the past 400 years.

The analysis covered diseases like plague, smallpox, cholera, typhus and novel influenza viruses and found “considerable variability” in the rate at which pandemics occurred in the past, but researchers also found patterns that allowed them to sketch out the probabilities of similar-scale events happening again, the study states.

In the case of the Spanish flu, which is estimated to have killed more than 30 million people worldwide between 1918 and 1920, researchers found the probability of a similar pandemic occurring to be 0.3 per cent to 1.9 per cent per year over the time period studied. Basically, the study posits it is statistically likely that a pandemic of similar “extreme scale” would occur within the next 400 years.

The study also shows the rate of risk for intense outbreaks is increasing rapidly.

Based on the growing rate of novel pathogens such as SARS-CoV-2 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.

Using their new calculations, researchers estimate in the study that a pandemic similar in scale to COVID-19 is likely within a span of 59 years, something noted by the authors as “much lower than intuitively expected.”

"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," Pan said in the release.