The virulence of diphtheria bacilli under these eirctunstances is illustrated as follows: A girl, aged 8, had a mild attack of diphtheria, and after two months in hospital was, at the request of her parents, sent home, though the bacillus was still present in the throat. A week after her return a companion living in the same tenement entered the hospital with a diphtheritic sore throat, though the bacillus was not found. Three days later, the sister of the first patient, and fourteen days later the sister of the second, were received into the hospital, suffering from diphtheria, in each of which the bacillus was found. A bacteriological examination of the first patient's throat eighty-four days after disappearance of the membrane showed that the virulent diphtheria bacillus was still present. Holger Prip (Zeit. f. Hyg. u. Infectsk., B. xxxvi, H. 2, 1901).
The following section from the Bul letin of the New York Board of Health is of interest in this connection:— "It has been the practice of the De partment to plot upon a city map the location and date of every case of diph theria in which the diagnosis had been settled by bacteriological examination. After several months the map presented a very striking appearance. -Wherever the densely settled tenements were lo cated, there the marks were very numer ous, while in the districts occupied by private residences very few cases were indicated as having occurred. It was also apparent that the cases were far less abundant, as a rule, where the tenements were in small groups than in the regions of the city where they covered larger areas. At the end of six months there were square miles in which nearly every block occupied by tenement-houses con tained marks indicating the occurrence of one or more cases of diphtheria; and in some blocks many (15 to 25) had oc curred.
"As the plotting went on, from time to time the map showed the infection of a new area of the city, and often the subsequent appearance of an epidemic. It was interesting to note two varieties of these local epidemics: in one the sub sequent cases evidently were from neigh borhood infection, while in the second variety the infection was as evidently de rived from schools, since a whole school district would suddenly become the seat of scattered cases. At times, in a certain area of the city from which several schools drew their scholars, all the cases of diphtheria would occur (as investiga tion showed) in families whose children attended one school, the children of the other schools being for a time exempt."
A number of epidemics have been traced to infected milk, the infection arising from the presence of diphtheria among those engaged in handling the milk. Certain English observers have also claimed to have discovered a specific disease among milch cows, characterized by an eruption of vesicles and pustules upon the udders and teats, accompanied by the presence of the diphtheria bacillus in the local lesions, and capable of being reproduced by infectious of the bacilli.
Other outbreaks of diphtheria have been attributed to bad drainage, defect ive sewers, or the presence of an abun dance of decomposing organic matter. It is also held that certain domestic animals —pigeons, cats, etc.—are susceptible to diphtheria and may be the means of transmitting it to man.
However much or little insanitary sur roundings may contribute to the devel opment of diphtheria, the active and essential cause must be the diphtheria bacillus, and our hope of limiting the ravages of this disease must be based upon control of the individual cases, each of which is a focus for the farther spread of the infection.
The tenacity to life of the bacillus outside the body is remarkable. Hof mann found that it would live for one hundred and fifty-five days on blood serum; Loeffler and Park for seven months; and on gelatin Klein found it living after eighteen months. On bits of dried membrane found living bacilli after fourteen weeks, Park after seven teen, and Roux and Yersin after twenty weeks. Abel says that, dried on silk threads, they may live one hundred and twenty-two days and upon a child's play. thing, kept in a dark place, he found the bacilli alive after five months.
The period of incubation of diphtheria varies from two days to a week. It is doubtless affected by the number and virulence of the organisms present and by the resisting power of the patient. In most cases it is impossible to determine the time of exposure, much less that of infection. Second attacks of diphtheria are rare, but do occur. In one case ob served at the New York Foundling Hos pital, a boy of 4 had crcup in March.
The diphtheria bacilli were demon strated in cultures from the throat. Antitoxin was given and he recovered. Twenty-five days later, having been ap parently well in the meantime, he devel oped tonsillar diphtheria, which ex tended to the larynx, pneumonia devel oped, and death followed, thirty-four days from the conclusion of the first at tack.