212 INFECTION AND IMMUNITY 



can be conveyed from the very outset of the attack, 

 and probably in protracted cases for several months 

 just how long has not been definitely determined. 

 The susceptibility to the disease among children is 

 very great, but diminishes with advancing age. Adults 

 and even old persons, however, occasionally suffer an 

 attack. The immunity resulting from a single attack 

 is very great. 



The number of deaths reported from whooping- 

 cough, in the United States, during the census year 

 1900 was 9958. The death-rate per 100,000 of the 

 population was 12.7. The comparatively non-fatal 

 character of the disease is shown by these figures, as 

 it is one of the commonest and most widely spread of 

 infectious diseases. A considerable number of deaths 

 are, however, indirectly due to an attack of this dis- 

 ease as it is recognised as one of the predisposing 

 causes of tuberculosis. The death-rate in the United 

 States is more than twice as great among coloured 

 children as among whites. There has been a con- 

 siderable decrease in the mortality from whooping- 

 cough during the ten years ending in 1900. The 

 census returns show that the greatest mortality occurs 

 among infants, less than one year of age. Beyond 

 the age of five the mortality is very slight. The 

 months of greatest mortality are March, April, and 

 August ; of lowest, October and November. 



