BACILLUS TYPHOSUS 127 



4. The duration of the immunity is not yet deter- 

 mined, but is assuredly two and one-half years and 

 probably longer. 



5. Only in exceptional instances does its administra- 

 tion cause an appreciable degree of personal discomfort. 



6. It apparently protects against the chronic bacillus 

 carrier and is at present the only means by which a 

 person can be protected against typhoid under all 

 conditions. 



7. All persons whose profession or duty involves 

 contact with the sick should be immunized. 



8. The general vaccination of an entire community 

 is feasible and could be done without interfering 

 with general sanitary improvements, and should be 

 urged wherever the typhoid rate is high. 



By the use of this prophylactic, typhoid fever has 

 practically disappeared from the United States Army. 



Vaccines have also been used during an attack of 

 typhoid, but the results, while satisfactory to some 

 observers, cannot be said to be generally acceptable. 



Paratyphoid Fever. There is a variety of enteric 

 fever called paratyphoid fever. This is caused by the 

 Bacillus paratyphosus, an organism closely allied to 

 the true typhoid bacillus and only separated from it by 

 its ability to ferment certain sugars and the quantity 

 of acid it produces under artificial conditions. In para- 

 typhoid fever, however, the blood will not clump 

 (agglutinate) the true typhoid bacillus, but does have 

 such an action upon the paratyphoid bacillus. In 

 this form of fever the course is shorter, the attack is 

 milder, and complications are much less frequent. 

 There is usually no ulceration of Peyer's plaques and 

 therefore hemorrhage from the bowel is of extreme 



