The COVID-19 pandemic may be the deadliest viral outbreak the world has seen in more than a century. However, statistically, significant pandemics aren’t as rare as we may think.
That’s according to a study released last month that appeared in the Proceedings of the National Academy of Sciences. It gathered and examined a record of novel disease outbreaks over the past 400 years to determine the intensity of those events and the likelihood of them recurring.
One of the authors is Dr. Anthony Parolari, assistant professor of civil, construction, and environmental engineering at Marquette University. "The approach that we take and the information that we've been able to gain through this statistical analysis tells us that the risk of an epidemic is actually more likely than we would think intuitively," says Parolari.
The study examined records of epidemics ranging from the years 1600-1945. The data sets examined for the study included the duration of the epidemics, number of deaths, and the percent of the global population that died at the time to calculate the intensity according to Parolari. Despite its timeliness, given the current global pandemic, COVID-19 data was excluded.
Parolari explains, "So some of the epidemics that have occurred, we weren't able to include in the data set. COVID-19 is one of them. And so one of our rules for disclosing an epidemic from the data set was that it was ongoing."
Another criteria was that the epidemic included in the data set couldn't have been controlled by means like vaccines and other interventions.
The study finds that the likelihood of someone experiencing an epidemic in their lifetime is highly probable. "What we find is that an epidemic, like COVID-19, has a yearly probability of about 2%. And if we run that through a risk calculation, we find that a person living about 100 years has a 38% probability of experiencing a pandemic like COVID-19," reveals Parolari.
He notes that several factors that may be contributing to the likeliness of an epidemic happening could be population growth, changes in food systems, and more frequent contact between people and animals that harbor these diseases.
Parolari expresses, "One thing that we hope our study does is spur or inspire more research to better understand how the human population and how we're changing the environment is, you know, increasing or changing the risk of these epidemics."