As part of research published last month in scientific journal Cell, Fauci and Morens point out that “the past decade has witnessed unprecedented pandemic explosions”—citing swine flu, Zika virus and Ebola fever—and suggest that “COVID-19, recognized in late 2019, is but the latest example of an unexpected, novel, and devastating pandemic disease.”

“One can conclude from this recent experience that we have entered a pandemic era,” they state. “The causes of this new and dangerous situation are multifaceted, complex, and deserving of serious examination.”

Fauci and Morens explain that although newly emerging infectious diseases have been threatening humans since the Neolithic Revolution some 12,000 years ago—when hunter-gatherers settled into villages to domesticate animals and cultivate crops—the past decade has seen a sharp spike in the number of novel coronavirus outbreaks after more than a century without them.