INFECTIOUSNESS OF AIR FROM A TUBERCULOSIS WARD - ULTRAVIOLET IRRADIATION OF INFECTED AIR - COMPARATIVE INFECTIOUSNESS OF DIFFERENT PATIENTS

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Abstract
Studies previously reported on the aerial dissemination of pulmonary tuberculosis were extended for 2 years in order to exclude the possibility of infection transmitted by other routes and to estimate the relative infectiousness of different categories of patients. Air from a tuberculosis ward was delivered unchanged to one animal-exposure chamber (the test chamber) and was intensely irradiated with UV light before delivery to a 2d animal-exposure chamber (the control chamber). Since there were no infections in the control chamber, the 63 infections occurring in the guinea pigs in the test chamber must have been carried to these animals by the air from the tuberculosis ward. In the case of 50 of the 63 infected guinea pigs, the patient who was the source of the infection was identified. This was done by matching the drug susceptibility of the organisms in the patient and in the guinea pigs, and by matching the time of infection of guinea pigs with the time the patient occupied the ward. By incriminating not only the air from the ward but specific patients who occupied the ward as the source of infection in the guinea pigs, air-borne transmission of tuberculosis from patient to guinea pig in inferred. Reasons for believing that the tubercle bacilli were transmitted as droplet nuclei are presented. The infectiousness of untreated patients with drug-susceptible organisms was much greater than that of the patients on chemotherapy, regardless of whether the latter harbored resistant or susceptible organisms. The infectiousness of the untreated patients with drug-resistant organisms was intermediate. Calculations suggest that one patient with tuberculous laryngitis, who infected 15 guinea pigs in 3 days, was more infectious than the average child with measles.

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