PUBLIC HEALTH 



23 



posaL That these bacteria should be more attenuated than 

 those occurring in drinking water does not seem probable. 

 Many facts show that flies are a very important factor in the 

 dissemination of typhoid fever. The greater frequency with 

 which persons on country vacations contract the disease is 

 very striking, although this may, of course, be attributed to 

 bad water supply. Other opportunities for infection, aside 



Fig. 0. Seasonal Prevalence of Typhoid Fever in Several States; solid line. 

 New York; dotted line, Alabama; dashed line, Washington. 



from the fly, are, however, no greater there than in the city. 

 In other parts of the world where the water supply is reason- 

 ably good, e.g., certain South American cities, typhoid flour- 

 ishes to an alarming extent, due undoubtedly to excessive 

 soil pollution, where flies can almost instantly transfer ma- 

 terial from typhoid carriers to food, while the latter is abun- 

 dantly exposed on the streets for sale to be eaten on the spot. 

 In our own country the seasonal incidence of typhoid fever 

 corresponds to some extent with fly prevalence, and still 

 more significant is its greater sunnner prevalence in regions 

 where systems for sewage disposal are not generally installed. 

 This disparity is shown on the accompanying chart (Fig. 9,) 

 which gives data for two of our eastern states, New York and 



