Doctors may not have noticed or reported these earlier cases, at first, owing to the similarity between pox symptoms and the symptoms of some common sexually transmitted diseases such as herpes. In other words, the current outbreak began, and expanded, without anyone noticing at first.

The virus had a big head start, which helps to explain why, months later, it still has the advantage. “By the time we recognized that cases were happening, we were already behind,” Lawler said.

Prompt diagnosis is the key to containing a dangerous virus quickly. If officials know where the virus is concentrated in the early days of an outbreak, they can isolate infected people, conduct contact-tracing to identify vulnerable populations and deploy therapies and vaccines and to treat the infected and protect the uninfected. (Lucky for us, widely available smallpox vaccines work just fine against monkeypox.)…

The worst outcome isn’t hard to imagine—10,000 cases could quickly bloom into 100,000 cases. Then 1 million. Various experts and agencies disagree over the precise definition of “pandemic,” but if the pox outbreak doesn’t already qualify, it’s increasingly likely that it will in the weeks to come. At that point, the world will be contending with simultaneous pandemics.