When a teenager in Idaho contracted the bubonic plague in early June, it made a few headlines because it was the first case in Idaho in 26 years. Half a millennium after it killed an estimated 60% of the European population, the specter of the Black Death still looms large in Western consciousness — gangrene, swollen lymph nodes, seizures — a horrific relic of days long past. But actually, although the bubonic plague has long been understood, it has never been eradicated.

In fact, outbreaks of the bubonic plague have been fairly common across the US since the early 20th Century.  The last widespread outbreak happened in Los Angeles in late 1924, when 30 people who lived within a few blocks of each other contracted the bubonic plague, which developed into pneumonic plague, as it virtually always does when left untreated. Altogether, 24 people died in that outbreak, though newspapers at the time referred to it as a strain of pneumonia to prevent panic — and possibly anti-racist sentiment as the neighborhood affected was home to a large population of Mexican immigrants, including Patient 0. Antibiotics, which are still very effective against the bubonic plague, did not come into widespread use until the 1950s. Before that development, outbreaks were not unusual throughout the west, particularly in California, New Mexico, Arizona and Oregon.