Statistics may not be for everyone. They can be confusing, bad actors may cherry-pick what they want, and they can sometimes tell us things that we don't want.
A new statistical study, for example, has shown that large pandemics occur more often than you might think. The team discovered that a pandemic of similar impact as COVID-19 is only about 2% likely to occur each year.
If you multiply that across our entire lives, it means that we have a 38 percent chance to experience a major one at least once in our lifetimes. And the odds are only getting worse.
William Pan, Duke University global health researcher and environmental health expert, stated that "the most important takeaway from this is that large pandemics such as COVID-19 or the Spanish flu are likely to occur."
The historical record of epidemics between 1600 and now was examined by the team. There were 476 epidemics that they found, with approximately half of them causing at least 10,000 deaths. There were 145 epidemics that caused less than 10,000 deaths. We know of 114 other ones, but we don't know the exact number.
Importantly, infectious diseases that are active at the moment were not included in the analysis. This means that there was no COVID-19 or HIV and no malaria.
To analyze the data, the team used detailed modeling with a generalized Pareto Distribution. They found that the annual number of epidemics was extremely variable and that an extreme epidemic such as the 1918-1920 Spanish flu had a probability of happening somewhere between 0.3 to 1.9 percent every year for the past 400 years.
The paper states that "the slow decay of probability with epidemic intensity implies that extreme epidemics may be relatively likely," a property that was previously not detected by stationary analysis and short observational records.
However, this isn’t a constant probability. It’s growing.
Over the past 50 years, there have been increasing numbers of pathogens that spread through humans. SARS-CoV-2 is the obvious example. But even over the past few decades, we have had bird flu, swine flu and Ebola.
The team wrote that "together with recent estimates of rising rates of disease emergence in animal reservoirs associated to environmental change", this finding suggests that there is a high likelihood of witnessing pandemics like COVID-19 (probability to experience it in one’s lifetime currently at 38 percent), which could double in the coming decades."
Even though we're recovering from the current outbreak, we need to be aware that there may be another potentially life-threatening pandemic in the future.
If we play our cards well, our resources and response to COVID-19 will be able to prepare us for the next pandemic.
Pan stated that this shows the importance of having a rapid response to large-scale outbreaks and building the capacity to monitor them at both the local and global levels. He also suggested that Pan should establish a research agenda to understand why these large outbreaks are more frequent.
Statistics are a factor in the next pandemic. Let's hope that we don't forget about the past.
The research was published in PNAS.
