An old rule of thumb in pandemic research was that such events happened about three times every century, said David Finnoff, an economist at the University of Wyoming College of Business. So far this century, the world has already confronted an array of viral scares, including SARS in 2002 and 2003, the swine flu (also known as H1N1) in 2009, MERS in 2012, Ebola in 2014 to 2016, Zika in 2015 and Dengue fever in 2016.

The incidence of infectious disease events has more than doubled from the 1940s to 1960s, according to EcoHealth Alliance, a New York-based nonprofit research group that built a database tracking disease events globally. The rate of such incidents surged in the 1980s with the advent of HIV and is now rising, says Peter Daszak, the group’s president.

“They’re increasing exponentially,” he said.

Already this century infectious disease pandemics—not counting the common influenza—have claimed more than 300,000 lives globally, according to Harvard researchers David Bloom and Daniel Cadarette.

Mr. Daszak estimates pandemics could cost as much as $23.5 trillion over the next 30 years. That estimate includes not just lost economic activity and property, but also the statistical value of lost human lives.