Those optimistic tales, told when the flu struck Philadelphia, that a bacterium that caused the flu had been isolated, turned out to be untrue. Yes, the bacterium was found. But no, it did not seem to lead to a treatment or a vaccine. The cause of the disease remained a mystery. In 1918, the widely proclaimed discovery of Pfeiffer’s bacillus turned out to be a false trail. The influenza virus was beyond anyone’s grasp.
