APPLICATIONS AND SOURCES OF ULTRAVIOLET 75 



is approved for general hospital use by the American Medical Association 

 (1948). 



Lurie (194G) and Vandivicre ct at. (1949j ha\e shown that tubercle 

 bacilli, either in sputum or air-borne, are readily killed by practical 

 exposures to ultraviolet. Wells and Ratcliffe (1945; Wells et al., 1948) 

 have shown that, in experimental animals, tuberculosis is spread mostly 

 l)y air-borne organisms so small that they remain suspended in air for long 

 periods. These studies suggest a unique value for ultraviolet air sani- 

 tation in tuberculosis hospitals and perhaps even in some homes. 



Schools. The promising results in hospitals led at once to trials in 

 public schools. Wells et al. (1942) and Wells (1945) in Swarthmore 

 and Wells and Holla (1950) in Pleasantville studied the spread of measles 

 and chicken pox as typical of respiratory diseases in general to find that 

 ultraviolet air disinfection suppressed the epidemic occurrence of these 

 diseases in the sense that their incidence was spread out over longer- 

 than-usual time intervals. This modification of the pattern of epidemic 

 spread was thought worth while in spite of some uncertainty as to a 

 significant long-run reduction in the total cases. 



Only measles and chicken pox were studied as respiratory diseases, 

 typical in their air-borne manner of spread but atypical in the individual 

 immunity they impart, with the preconception that influenza and the 

 common cold could not be studied directly because of their indefinite 

 diagnosis, their spread in every environment outside the schools, and the 

 almost universal susceptibility to them. As anticipated, air disinfection 

 provided no measurable effect on the incidence of colds and influenza 

 among the school children, and Downs (1950) reported no effect in a 

 surrounding community. The studies by Wells and Holla (1950) showed 

 that measles and chicken pox are too completel}^ typical of respiratory 

 diseases to simplify greatly the study of their epidemiology in schools 

 since two-thirds of their spread occurred outside the school coverage of 

 the ultraviolet installation. 



In large consolidated schools served by busses from small towns and 

 the surrounding country, Perkins et al. (1947) hoped to study also measles 

 and chicken pox with a minimum spread outside the school environment. 

 There was early indication of some effect on the epidemic spread of the 

 diseases in the schools, but there was also subsequent evidence of their 

 spread in the busses, perhaps enough to blanket the marginal effect of the 

 air disinfection in the school buildings. 



Ultraviolet air disinfection is justified in school rooms as a supplement 

 to air sanitation by ventilation, especially in northern latitudes. It has a 

 place as a general sanitary measure along with dust suppression, wash- 

 room sanitation, and habits of personal cleanliness which may be taught 

 and practiced in schools regardless of their effectiveness outside the 

 school. 



