DIPHTHERIA (a) Infective Agent.—Mycobacterium diphtherice.
(b) Source of Infection.—Typical or atypical cases or carriers.
(c) Exit of Infective Agent. Most commonly in the secretions of the mouth and nose, which are contaminated from lesions situated in the nose and throat. Less frequent and of lesser importance are lesions on the conjunctiva, infection of wounds and of the vagina.
(d) Routes of Transmission.—By direct or indirect contact, and by milk or milk products contaminated with bucco-nasal secretions from cases or carriers.
(e) Incubation Period.—Usually 2 to 5 days, sometimes longer in the case of incubatory carriers.
(f) Period of Communicability.—Until virulent bacilli have disappeared from the secretions and lesions as determined bac teriologically. Their persistance is variable, in 75 per cent. of the cases they disappear within two weeks, in 95 per cent. within 4 weeks. In exceptional carriers they may persist for 2 to 6 months.
(g) Entrance of Infective Agent into the Body.—The organism does not penetrate the physiological interior of the body. Most commonly it gains access to the mouth or nose.
(h) Methods of Infected Individual.-1. Diag nosis: Clinical manifestations together with baCteriological examination, or the latter alone.
2. Isolation: Until two consecutive negative cultures are secured from both the nose and the throat, taken not less than twenty-four apart and not less than 4 hours subsequent to the local employment of antiseptics. Some authorities advocate the termination of isolation with diphtheria bacilli present providing the latter give negative virulence tests.
3. Artificial Immunization: Susceptible contacts who are found to be carriers should be given prophylactic doses of antitoxin. Contacts in whom the diphtheria bacillus is not found and who give a positive Schick reaction, indicating their susceptibility to diphtheria toxin, should be actively immunized by toxin-antitoxin mixtures, the administration of which is controlled by the Schick test.
The Schick test consists in the intracutaneous injection of of the M. L. D. of a diphtheria toxin contained in .r to .2 C. c. of saline. A negative reaction is a sign of immunity, and a positive reaction a sign of susceptibility. Less than of an antitoxin unit per c.c. of blood makes an individual susceptible. A positive reaction runs the following course: In from 12 to 24 hours there is a trace of redness 24 to 48 hours there is a reaction 3 to 4 days the reaction is at a maximum and waning.
3 to 6 weeks there is a circumscribed area of scaling and for pigmentation. Pseudo reactions have a more rapid course and leave no pigmentation.
Active immunization against diphtheria toxin is accomplished by injecting overneutralized mixtures of toxin and antitoxin. These mixtures should contain per c.c. from eighty to ninety per cent. of the limes plus dose of toxin and one antitoxin unit. One c.c. is a dose and it should be given subcutaneously and repeated at intervals of six to eight days. This method of immunization is employed upon susceptibles to the toxin as re vealed by the Schick test.
The employment of diphtheria antitoxin as a therapeutic agent effected a gross reduction in the mortality from diphtheria of 85 per cent. The present mortality from diphtheria is largely due to either its delayed administration or its employment in insufficient amounts. The following doses are recommended by Park and Biggs as minimal: In any event its administration should be continued until the desired result is secured. it is better to give the above indi cated amounts as one single dose and add additional quantities as the course of the case may require. The quickest results and the maximum benefit is secured from the intravenous route of injection. In order to guard against anaphylactic reactions, the possibility of the patient's sensitization to horse serum must always be borne in mind, and de-sensitization performed if necessary.
4. Quarantine: Of all exposed persons until shown to be free from infection by bacteriological examination.
5. Concurrent Disinfection: Of all secretions of the infected person and articles which have been contaminated therewith.
6. Terminal Disinfection: Thorough airing and scrubbing of the isolation quarters.
General Measures.— 1. Pasteurization of the public milk supply.
2. Application of the Schick test to all children.
3. Application of the Schick test to all contacts and the active immunization of all found to be susceptible.
4. Active immunization by toxin-antitoxin mixtures of all susceptibles.
5. Determination of the presence or absence of carriers among the population at large.