A new pandemic as bad as (or worse than) COVID-19 has an up to one in fifty chance of happening in any given year – and the danger is rising, a new study concludes. So, while it may feel as though we are all unlucky to be living through such a global disaster, most of us could expect to experience it again.

The long gap since at least 30 million people died of the "Spanish flu" lulled many of those unaffected by AIDS into a false sense of security when it comes to pathogens. Having eliminated smallpox and beaten down many other diseases with antibiotics and vaccines, some acted as if humanity had moved past being at the whim of microbial invaders.

However, Duke University's Dr William Pan has stated that COVID-19 is no outlier. He's an author of a paper in Proceedings of the National Academy of Sciences looking at disease outbreaks over the last 400 years, concluding these events are common – and getting more so.

“The most important takeaway is that large pandemics like COVID-19 and the Spanish flu are relatively likely,” Pan said in a statement. 

The authors looked at both the scale and frequency of disease outbreaks since 1600 where no effective treatment was available at the outset, nor prevention methods better than stopping people coughing on each other.

Had they limited themselves to diseases that killed millions, the sample size might be too small to offer much guidance. However, the authors used a sample of 476 epidemics – many that were less lethal – finding an inverse relationship between frequency and death toll. Diseases still out there, such as COVID-19 and HIV, were excluded from the sample since the final toll is not yet known.

The risk of a disaster as bad as the Spanish Flu, which killed over 2 percent of the global population at the time, is between 0.3 and 1.9 percent in any one year, the paper gloomily concludes. Less catastrophic – but still devastating – outbreaks are considerably more likely.

If that is not depressing enough, the authors think the dangers are rising, as denser populations, increased travel, and human encroachment on natural disease reservoirs outpace advances in disease control.

The team also made more speculative calculations, which they chose not to include in the paper, estimating the chance of a horrific disease that could end human life entirely. That, they think, would take 12,000 years to become statistically likely – which still seems alarming for a species that has survived 20 times that long, mostly too dispersed for infectious diseases to take hold.

“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.