1950, Serratia marcescens
During the late 1950's, the United States Navy conducted an experiment that included spraying extremely large quantities of S. Marcescens over San Francisco. It was said that there was one point, in which a cloud made out of S. Marcescens formed up to about two miles long. The idea was to simulate a biological attack from another nation. (Why? Because.)
Because why not?
The experiment was "successful" in the terms that eleven people developed rare, severe urinary tract infections, and one of which, died; Three days after the experiments began. Cases of pneumonia also increased after the experiments began.