Wells Revisited: Infectious Particles vs. Quanta of Mycobacterium tuberculosis Infection Don't Get Them Confused
Perhaps the clearest thinker on the subject of airborne infections to date was William Firth Wells, a sanitary engineer born in Boston in 1887. Wells trained in the military and later conducted seminal experiments at Harvard University between 1930 1937, and at the University of Pennsylvania 1937 1944, producing clear evidence for the airborne spread of infection. Charles Chapin, the influential health officer of Providence, Rhode Island, had dispelled the importance of airborne infection in his 1910 monograph, "Sources and Modes of Infection" [1] Well's challenge to that belief is summarized in his still relevant 1955 masterwork, "Airborne Contagion and Air Hygiene: An Ecological Study of Droplet Infections" published by Harvard University Press [2] In the preface Wells attributes the crucial distinction between droplet nuclei (airborne inhalable dried residua of larger respiratory droplets) and germ laden dust (non inhalable larger respiratory droplets) to Richard L. Riley, a medical student working with him at Harvard at the time. Riley became Wells' lifelong protege, and between 1957 1962 conducted the classic human to guinea pigs studies in Baltimore that Wells had long before envisioned to prove beyond doubt that contact with contaminated air was sufficient to result in Mycobacterium tuberculosis transmission[3 6] That brilliant experiment quantified infection, showing great patient to patient variability in infectious source strength, and also, importantly, that effective chemotherapy almost immediately stopped human to guinea pig transmission.