THE ENTERIC GROUP (a) Infective Agents.—Bacterium typhosus, Bacterium para typhosus A, Bacterium paratyphosus B.
(b) Source of Infection.—Typical and atypical cases and carriers.
(c) Exit of Infective Agents.—Principally in the feces and urine. Of lesser importance are the sweat, sputum, human milk and pus.
(d) Routes of Transmission.—By direct or indirect contact, also by water, milk or dairy products, shell-fish and other raw or uncooked foods contaminated with excrement, and through mechanical transmission by house flies (See Fig. 3). These other routes will be considered in detail later.
(e) Incubation Period.—From 7 to 23 days, averaging ro to 14 days.
(j) Period of Communicability.—From the appearance of the prodromal symptoms, throughout the illness and relapses, during convalescence, and until the excrement is bacteriologic ally found to be free of the bacillus. Carriers may harbour the organisms for a long period of years.
(g) Entrance of the Infective Agents into the Body.—By the mouth to the intestinal tract.
(12) Methods of Control. The Infected Individual.-1. Di agnosis: Clinical manifestations, confirmed by bacteriological examinations of the blood, feces, and urine; and by the Widal test.
2. Isolation: In a fly proof room, preferably under hospital conditions for such cases that cannot command adequate sanitary environment and nursing care in their homes.
3. Artificial Immunization: Bacterial vaccines have given highly satisfactory results as a prophylactic. They should be employed on susceptibles who are known to have been exposed or who are suspected of being exposed.
Furthermore, their widespread employment among the popu lation at large should be encouraged. Best evidence of their value is afforded by the experience of the American and other armies. Thus in the Maneuver Division of the U. S. Army at San Antonio, Texas in the summer of ion, with a mean strength of 12,8or men, all vaccinated, there were from March Toth to July loth, only two cases of typhoid. One of these cases had not been vaccinated, the other had not completed the course. As a consequence of vaccination, there was in the period between I9o9 and 1914, only one death from typhoid in the army (about 8o,000 men), while the death rate in the country at large averaged over 16.5 per hundred thousand.
The immunity varies in degree and also in duration, though when produced by a series of inoculations on the army plan, it probably may be depended upon for two or three years.
Combined vaccines, prepared from the typhoid bacillus and the alpha and beta paratyphoid bacilli are preferable, of which the typhoid bacillus comprises so per cent. of the organisms in suspension. The common suspensions have approximately two billion dead bacteria per c.c. The initial dose is one billion and later doses two billion bacteria. At least three and pre ferably four inoculations should be given. The inoculations are made subcutaneously at the point of insertion of the del toid, after the site has been painted with tinture of iodine. The inoculations should be spaced about one week apart. Most people only experience a local reaction. The general reaction, which appears within twenty fours and rapidity subsides, is never serious and consists of malaise, muscular soreness and fever.
4. Quarantine: None.
5. Concurrent Disinfection: Of all bowel and urinary dis charges and of all objects contaminated by them.
6. Terminal Disinfection: Cleaning.
General Measures.—i. Purification and disinfection of public water supplies.
2. Pasteurization of public milk supplies.
3. Supervision of food supplies and of persons employed as food handlers.
4. Prevention of fly breeding.
5. Sanitary disposal of human excreta.
6. Extension of the public immunization by vaccination as far as practicable.
7. Recognition of typhoid carriers and their exclusion from the handling of foods to be consumed by others.
8. Systematic searches for carriers.
co. Exclusion of suspected milk supplies pending the dis covery of the person or other cause of the infected condition of the milk.
ro. Exclusion of a water supply if contaminated, until ade quately treated with hypochlorite or other disinfectant, unless the water used for toilet, cooking and drinking purposes is boiled before use.