4i6 THE BACTERIAL ASPECTS OF PASTEURIZATION 



Infantile paralysis {poliomyelitis). — ^To this long list of milk-borne diseases must 

 now be added infantile paralysis. Two small outbreaks, one at Cortland (N. Y.) and 

 another at Spring Valley (N.Y.), have been described which seem attributable to 

 milk infected by a case of the disease during the acute stage on the dairy farm. Re- 

 cently, a third and larger outbreak occurred at Broadstairs (England). 



Dingman' reported a group of eight cases in and around Spring Valley (N.Y.), 

 all of which had their onset between July 20 and 22, 191 6. All the cases used raw 

 milk from the same two-cow dairy. Three families who used this milk but boiled it 

 escaped. There was a case, a four-year-old child, at the dairy who became ill with the 

 disease on July 4. 



The outbreak in Cortland occurred December 14-25, 1925.^ All the eight cases, 

 which were widely separated, occurred among the users of the same supply, which 

 was only 4 per cent of the milk supplied the city. There was a paralytic case on the 

 dairy farm, and this individual milked the cows and handled the milk for a period of 

 four days (December 7-1 1) while in the acute stage of the disease. The milk was not 

 pasteurized, and no case occurred among those who first boiled the milk. 



In October, 1926, an epidemic of seventy-two cases of infantile paralysis occurred 

 in Broadstairs (England), which was studied by Aycock.^ The explosive nature of 

 the epidemic is shown by the occurrence of seven paralytic cases on October 10 and 

 six on October 11 ; fifty-eight of the cases occurred between October 10 and 20. Most 

 of them were among the better class. There was clear epidemiological relationship with 

 a particular milk supply, fifty cases occurring among known users of this milk, and 

 nineteen others in individuals supplied by another dealer who was known to have 

 purchased a part of the suspected milk supply. 



Summary and discussion of milk-home diseases. — All the outbreaks have invari- 

 ably been traced to the use of raw milk. There is no authentic record of a milk-borne 

 epidemic due to properly pasteurized milk. Raw milk is likely to be dangerous milk. 

 Contrary to the common belief, most milk-borne epidemics have been associated with 

 milk of an unusually high grade — even certified milk has been responsible for out- 

 breaks of diphtheria, scarlet fever, and septic sore throat. Most of the serious infec- 

 tions get into milk directly and sometimes indirectly from human sources. Only in 

 occasional instances are the diseases of cattle (other than tuberculosis) transmitted to 

 man. Cream, ice-cream, and other fresh-milk products are quite as dangerous as the 

 milk from which they are obtained. 



METHODS OF PASTEURIZATION 



There are five methods of pasteurizing milk: (i) the flash method, (2) the hold- 

 ing method, (3) continuous flow, (4) the vat method, and (5) in the final container. 

 These are discussed in chapter xxxiii of this volume. 



DISCUSSION OF ADVANTAGES AND DISADVANTAGES 



Pasteurization prevents sickness and saves lives. Pasteurization is not ideal but 

 only an expedient. It is advocated because milk is likely to convey the viruses of a 



' Dingman, J. C: New York State J. Med., 16, 589. 1916. 



= Knapp, A. C, Godfrey, E. S., Jr., and Aycock, W. L.: J.A.M.A., 87, 635. 1926. 



3 Aycock, \V. L.; in press. 



I 



