The evidence in favor of the contagiousness of typhus fever is conclusive, and may be briefly stated as follows: When it breaks out in a community the disease not only attacks those persons who have been subjected to the same influence as the sick—as, for instance, members of their own families, occupants of the same house, etc.—but also those who have come from healthy localities to visit them. In fever hospitals it is rare for any member of the household who has not already had the fever to escape an attack, and the probability of his suffering is in direct proportion to the intimacy of his relations with the patients. Thus, the nurses are far more likely to be attacked than servants whose duties do not take them into the wards, except those employed in the laundry, who are so often affected by it that Murchison says it is difficult to find women who are willing to take the position. The spread of the disease may often be promptly arrested by the complete isolation of the first few cases, while free intercourse between the sick and the well is invariably followed by its extension, not only in the locality in which it first appeared, but to other localities. But the strongest argument in favor of its contagiousness is found in the fact that patients taken into a previously healthy place have frequently become the starting-point of an epidemic. In this way the disease has often been introduced by Irish immigrants into the cities on our seaboard, and even into some of our interior towns.
Actual contact is not necessary for the communication of typhus fever from the sick to the well. The contagion may be transmitted through the atmosphere. How far it will be transmitted in this way will depend upon many circumstances. In a spacious and well-ventilated ward it is probable that the presence of one or two patients with this disease does not seriously endanger the safety of the other patients, and that the only persons who run much risk of contracting it are the physicians and nurses, who are often compelled in the performance of their duties to inhale the emanations from the bodies of the sick. At the Pennsylvania Hospital, where cases of this disease are occasionally admitted, it has been usual to isolate them by placing them in a room a few feet distant only from the dining-room of the men's medical ward and separated from the ward by a short corridor. The steward of the hospital informs me that during his connection with it, which extends over a period of more than sixty years, he has never known the disease to extend to other persons, except on two occasions. One of these was during the epidemic described by Da Costa, when an unusual number of cases was received, and when one resident physician and two nurses contracted the disease. On the other occasion, which happened during my own term of service in the spring of 1881, a young Danish sailor appeared to have taken the disease from two British seamen. As it was ascertained positively that he had not entered the room in which these two seamen were isolated, and as his bed in the ward was one of the farthest removed from the room, and he had not therefore been more or as much exposed to the contagion as the other patients, it was difficult to understand why he alone of all of them should have suffered from it. The explanation was, however, found in the fact that he had been taken over to the women's ward to act as interpreter for a countrywoman who was not known at the time to be suffering from typhus fever, and that he had remained there some time in conversation with her. Murchison and Buchanan both assert also that typhus fever has never extended from the London Fever Hospital to the inmates of adjacent houses, even when it was itself one of a row of houses. If, on the other hand, several patients with typhus fever are placed in a crowded and ill-ventilated ward, the contagion will then be found to have acquired so much more virulence that few of the other patients will escape its effects.
There is also no question that typhus fever may be communicated by fomites. Numerous instances are on record in which the disease has been communicated by the wearing apparel and bed-clothes of patients, and we have already called attention to the frequency with which laundry-women in fever hospitals are attacked by it. The clothes of persons who are themselves free from the disease, but who have been in close attendance upon the sick for some time, are often also the medium of communication. Indeed, Murchison goes so far as to say that men who have not changed their clothes and "who have been living in close, ill-ventilated apartments and on short allowance, may at length have their garments so impregnated with the poison of typhus as to communicate it to others without being themselves the subjects of it," even if they have not been brought in contact with fever patients. The disease was communicated in this way, he thinks, in the famous Black Assize in 1750 by several prisoners to the court that tried them, although they were themselves free from it. On the other hand, with proper precautions there is little danger of the disease being conveyed by physicians to their own families or to other patients.
Some difference of opinion exists as to the stage at which typhus is most contagious. Many authors believe that it is more infectious during convalescence than at any other time, and base this opinion upon the fact that the removal of fever patients to the convalescent ward is very often followed by the occurrence of the disease among its other occupants; but this is probably due, as Murchison suggests, to the patients being allowed at this time to wear their own clothing, which has not been thoroughly disinfected. It is much more likely that the disease is more contagious during the stage when the febrile symptoms are most marked than during either the stage of convalescence or that of invasion. It would appear also, from the observations of Dr. Gerhard and others, that dead bodies do not readily communicate the contagion or that the contagious principle is easily counteracted after death. Still, there are several well-authenticated cases on record in which individuals have unquestionably contracted the disease from dissecting the bodies of patients dead from this cause.
A question of great interest naturally arises here, as to whether or not typhus fever ever occurs except as the consequence of exposure to a previous case of the disease. Is it, in other words, ever generated de novo? Authorities are divided upon this point, many contending that an independent origin is impossible, and others that it may occasionally arise in this way. Among the latter is Murchison, who adduces in support of the position he takes several instances in which poverty, with overcrowding and deficient ventilation, appears to have been the only cause of extensive outbreaks of the disease, as in the case of the Black Assize already alluded to. These cases the opposite party explain by assuming that the germs of the disease are capable of lying dormant for a long time until roused into activity by favoring circumstances. If the disease is caused, as we have shown there is good reason to believe it is, by the presence of a minute organism, this view does not seem to be untenable. Pasteur has demonstrated that the germs of the splenic fever of some of the lower animals may be deprived of their virulence by cultivation in appropriate liquids. If their virulence is diminished under certain circumstances, the assumption does not seem unwarrantable that under others it may be increased, and if we may draw this conclusion in regard to one form of microscopic growth, we may do the same for others; and the hypothesis is therefore not an unreasonable one that the typhus germ needs the atmosphere engendered by overcrowding for it to acquire the power to produce the disease.
PERIOD OF INCUBATION.—The period of incubation of typhus fever appears to vary considerably in length, but is usually about twelve days. In some cases the interval between exposure to the contagion and the occurrence of the first symptoms of the disease is asserted to have been considerably longer, and in one instance as long as thirty-one days; but it is probable that there has been in most, if not in all, of these cases a second exposure which has been overlooked. On the other hand, it is said to have followed at once upon exposure, as in cases reported by Gerhard, in one of which a nurse inhaled the breath of a patient whom he was shaving, and in an hour afterward was taken with cephalalgia and ringing in the ears, which were immediately succeeded by the other symptoms of typhus. In this and other similar cases which are on record it is difficult to exclude the possibility of a previous infection. In a case, however, reported by Murchison there would seem to be no reason to suspect that any such previous infection could have taken place, as the patient, the matron of an orphan asylum where there was no typhus, was taken ill immediately after opening a bundle of clothes which a child had brought with her from a fever hospital, and which had not been thoroughly disinfected.
SYMPTOMATOLOGY.—It will facilitate the study of typhus fever to give, in the first place, as most of the systematic writers on fever have done, a brief clinical sketch of the disease as it ordinarily occurs, and then afterward to consider its leading symptoms in greater detail.
GENERAL DESCRIPTION.—An attack of typhus fever is sometimes preceded for a few days by prodromata, such as a feeling of malaise, indisposition to exertion, pain in the head and limbs, anorexia, and vertigo; but it oftener begins abruptly with a slight chill, or more rarely with a decided rigor. This is followed in a short time by headache, by a marked rise of temperature, and by an increased frequency of pulse and respiration. Nausea is also occasionally present, and less frequently vomiting. The tongue is at first moist and covered with a thin whitish fur, but soon becomes dryish, and its coating is apt to assume a brownish appearance in a day or two. With these symptoms there are loss of appetite, great thirst, constipation, a dull, heavy expression of countenance, a dark, dusky hue of the face, and injection of the conjunctivæ. Mental confusion is early observed, so that, although the patient may be able to answer questions correctly when thoroughly roused, it is readily seen that his mind is working with difficulty. The sleep is very often disturbed by dreams, so that he awakes from it unrefreshed. Prostration and loss of muscular power are so decided from the very beginning of the disease that the patient is obliged usually to take to his bed at once, and it is much rarer to meet with walking cases of the disease than in typhoid fever. The urine is dense, scanty, and high-colored.
Usually, about the fourth day of the disease the characteristic eruption of typhus fever makes its appearance. It consists of numerous spots of irregular form with ill-defined margins and of a dark red or purplish color, occurring singly or in groups, and varying in size from that of a pin's point to two or three lines in diameter. They disappear at first under pressure, but in twenty-four hours become persistent, and in severe cases may be converted later into petechiæ. Besides this eruption there is another which consists of a faint, irregular dusky red, subcuticular mottling. The two eruptions together constitute the mulberry rash of Jenner, and have been variously described by different authors under the name of measly or morbilliform rash.
As the disease advances the prostration becomes greater and the pulse grows weaker. The tongue becomes dry and brown and trembles when protruded. Later, it is so dry and contracted that it can scarcely be put out of the mouth. Sordes collect about the teeth and lips, and the surface exhales a peculiar odor. The headache grows more severe or gives place to delirium, which may at first be active and violent, and then pass into the low and muttering form, or the delirium may be of the latter variety from the start. The sleeplessness of the early stages may continue, and the condition known as coma vigil not infrequently supervenes. The delirium is usually followed by stupor, which is more or less profound in accordance with the severity of the case, and which is accompanied by all the symptoms which characterize the so-called typhoid state, such as subsultus tendinum, picking at the bed-clothes, slipping down in bed, retention or incontinence of urine, and sloughing of the parts exposed to pressure. In this condition the temperature, although usually still considerably above normal, is lower than during the first week of the disease.