Coronavirus Is Spreading Because Humans Are Healthier

An outbreak of a deadly new coronavirus in Wuhan, China, has crippled the world’s second-largest economy and spread in 26 countries, causing more than 1,000 deaths and 43,000 laboratory-confirmed cases worldwide. A continent and two oceans away, the Ebola virus has been terrorizing the most heavily populated provinces of the Democratic Republic of Congo since August 2018. Even though the epidemic has slowed, three new cases have been reported in the past week.

When multiple international public-health emergencies occur at the same time, they may seem like evidence of microbes’ triumph over humankind. In fact, the opposite is true. Emerging infections like Ebola and the novel coronavirus—now dubbed COVID-19, as of yesterday—have a better platform to spread, somewhat ironically, because people are generally healthier than ever before.

For the first time in recorded history, bacteria, viruses, and other