Relapse

RELAPSE (from Latin recidivus - returning) - the return of a disease, i.e., its repetition in typical form directly after recovery or during the period of convalescence. As a rule, however, the relapse is an exact repetition of the former; it usually runs shorter and milder than the first illness, but in individual cases, relapses are accompanied by severe complications, sometimes with fatal outcomes. The frequency of relapses, the number of returns of the disease, and the intervals between them vary in different diseases and even in the same disease. For example, in relapsing fever, the recurrence of an attack (relapse) is characteristic of this disease, but depending on the epidemic, the number of relapses varies. In tick-borne relapsing fever, there can be up to 15 attacks. - In typhoid fever, the frequency of relapses ranges from 6% to 12% depending on the nature of the epidemic (Curschmann), and patients usually experience one relapse, rarely two or more. Each subsequent relapse runs milder and shorter than the previous one. Relapses are also observed in bacillary dysentery. Among streptococcal diseases, relapses are very common in erysipelas (see). Relapses are observed in scarlet fever (see). Relapses as a rule occur in brucellosis (see Malta fever). Some authors have described relapses in tetanus. They are observed in spirochetoses (for example, in relapsing fever, Weil's disease, etc.) and in protozoan diseases: amoebic dysentery, malaria (early and later seasonal relapses, see Malaria), in trypanosomiasis, etc. As for the clinical picture of relapses, all phenomena characteristic of a given infectious disease may recur. Often, however, the initial and final stages of relapse are somewhat shorter, the temperature elevation less prolonged than the first time. The characteristic features of the infectious disease are repeated, the temperature curve is identical to the original disease, and a series of clinical symptoms recur. In relapses of typhoid fever, intestinal hemorrhages and perforations of the intestines occur less frequently; changes in the intestine usually do not reach the previous degree (G. Jurgens).- The notion that relapses in infectious diseases, e.g., in typhoid fever, are associated with dietary errors, early rising, heavy physical exertion, and sometimes even with mental excitement, is erroneous; from the standpoint of our modern knowledge, these factors have no significance and play no role in the occurrence of relapses. The causes of relapses should be sought in the peculiarities of immunity (see below). Relapse should be distinguished from exacerbation of the disease (German authors - Nachschub, French - rechute); an infectious disease ending sometimes suddenly halts in its reverse development, temperature begins to rise, the severity of the disease increases, and new clinical symptoms appear. For example, in typhoid fever at the end of the disease, the lytic drop in temperature is delayed, fresh rose spots appear, leukopenia becomes more pronounced, the spleen enlarges again; the course of the disease is prolonged.- Close to the concept of relapse is the concept of reinfection (return infection). This term denotes a new infection of an organism that has already had a given disease. A secondary disease, separated by a large interval from the first, is commonly called a repeated disease. There is no fundamental difference between reinfection and repeated disease. They (reinfection and repeated disease) can be induced experimentally in animals and humans (e.g., in the infection of paralytics with relapsing fever), as well as observed under natural conditions. Thus, repeated diseases due to new infection are sometimes observed in persons who have had smallpox, typhus, malaria, etc., they are often observed in those who have had influenza, etc. In this case, we are talking about infection with the same pathogen that caused the primary disease. For example, infection of a person who had had the three-day form of malaria (P. vivax), the four-day form (P. malariae) should not be considered as reinfection, but as a new disease. The same applies, for example, to a person who had had paratyphoid B and then became infected with paratyphoid A. - Infection in reinfection occurs when the infectious agent penetrates from the external world (exogenous reinfection). Some authors also use the term endogenous reinfection when a new disease is caused by a pathogen that remained in the body after the transferred disease. In this case, local endogenous reinfection is possible, in the form, for example, of reactivation of a long-dormant tuberculous process at the old site or near it, or the transfer of infection from the old focus to a new site by the current of lymph or blood. In either case, one must assume either activation by some factor of an infection that was in a latent state, or a change in the reactive state of tissues under the influence of factors acting unfavorably on the body. It would be more correct to attribute all such cases of endogenous reinfections to relapses. But often in individual specific cases it is difficult to decide whether the infection occurred endo- or exogenously. For example, adult pulmonary tuberculosis is a reinfection of the body, which had a primary infection in childhood, with the tubercle bacillus. Until recently, most researchers saw the basis of this reinfection in a new exogenous infection; at present, many scientists assert that it is always the result of the transfer of infection within the body by the bloodstream, i.e., it has an endogenous origin. Close to reinfection is the concept of superinfection (superinfectio), i.e., a new disease against the background of an existing infection, caused by infection with the same type of microbe. For example, a syphilitic patient can become infected with it again. In superinfection, the disease again goes through its cycle, but to some degree different from the usual course of this disease. New infection can lead to the so-called asymptomatic superinfection. For example, in a rabbit completely cured of experimental syphilis and free from spirochetes, upon secondary infection with virulent spirochetes, no chancre appears. Spirochetes penetrate the body and cause a new infection, which can be proven by inoculation on animals (Kolle and others). Similarly, in people who have had syphilis, an asymptomatic superinfection or reinfection can occur, which, in the absence of treatment, will manifest itself in the development of late syphilitic diseases (tabes, paralysis, aortitis). In superinfection, there is an additional infection with the same virus, for example, in syphilis, the infection as it were sums up, an additional one of the same kind is 'superimposed' on the existing disease. In some cases, superinfection is as it were absorbed by the primary infection and manifests itself very weakly. In all these cases, immunity is weakened or disappears completely, or a partial immunity is developed, and only in that case are relapses or reinfection possible. Some authors explain the appearance of relapses by infection with different races of microorganisms in their virulence and pathogenic properties. Thus, relapses in relapsing fever Leishman and others explain by the formation of new generations of spirochetes from the resistant forms remaining after the first attack. These young generations are resistant to the immune bodies formed during the first attack. Levaditi and others noted the difference in the immuno-biological properties of relapse strains from strains isolated in the first attack. It is possible that relapses in other infectious diseases should be explained by simultaneous infection of the body with several races of microbes. Similarly, in reinfection and superinfection, it should be assumed that infection with different races of microbes occurs. If the body acquires a firm and stable immunity, mainly associated with the formation of bactericidal substances (Gabrichevsky, Leishman, V. Shilling), reinfection is impossible. Theoretically, it is possible to assume that a certain role in the origin of relapses is played by the variability of microbes. In general, the entire question of relapses, reinfections, and superinfection from the standpoint of immunity (see) cannot yet be considered sufficiently clarified and requires further study.- Clinicians also call relapse the return of a malignant tumor to its former site after its surgical removal, which is based on the incomplete removal of tumor elements. I. Dobreytser, E. Shnaynshnayder.