On October 3, 1924, a Los Angeles city health officer was called to the home of a railroad worker in the city’s Mexican district. A few days earlier, Jesus Lajun had developed a nasty swelling in his groin. His 15-year-old daughter, Francisca, meanwhile had a rattling cough and both were running high temperatures.

At first, the officer attributed the swelling in Lajun’s groin to syphilis and diagnosed his daughter’s symptoms as influenza, possibly the “Spanish” variety which had been the cause of so much suffering and death during the pandemic of 1918-1919.

But the officer was wrong and two days later Francisca was rushed to Los Angeles General Hospital. She never made it, dying in the back of the ambulance of a “double pneumonia”.…