When the WHO called the latest Ebola outbreak a Public Health Emergency of International Concern in mid-May 2026, the obvious question was how bad this one really is. The short answer is complicated. The longer answer starts with a number that genuinely bothers people who track these things. A Rare Virus, a Late Start This outbreak is driven by the Bundibugyo virus, or BDBV. It is the lesser-known cousin of the Zaire ebolavirus that caused the devastating 2014-2016 West Africa epidemic. BDBV has only surfaced a handful of times since 2007. There are no approved vaccines against it. No approved treatments. And when the outbreak was officially declared around May…