Infectious Diseases

Infectious diseases are caused by pathogenic bacteria or other microorganisms that multiply in the body and have a harmful effect on it. These organisms (germs and viruses) are capable of producing poisonous substances, or toxins, that poison the body. The chief source of infection is direct or indirect contact with the patient himself, the disease being communicated to others both before it has been recognized and the indi­vidual isolated, or transmitted after quarantine has been removed. According to the mode of infection contagious diseases may be classified as:

I. Infectious diseases in which the infecting organism penetrates through an abrasion or wound of the skin or mu­cous membranes. Such are, for example, pyogenic bacteria, causing septicemia, gonococcus infection, toxemia.

II. Infections caused by the pathogenic microorganisms through the respiratory tract are:

1. diseases due to various types of streptococci: rheumatic fever, quinzy, scarlet fever;

2. diseases due to filterable viruses: measles, mumps, smallpox, chicken pox, polyomyelitis.

III. Infections, generally bacterial, disseminated prin­cipally by the intestinal discharges, such as typhoid fever, dysentery, cholera.

In order to identify the causative microorganism bacteri­ological studies are performed which help to detect such microorganisms by direct examination under the microscope of the patient's blood, urine, stools, sputum or any patholog­ical material withdrawn from the body. The examination of the exudate on the tonsils, for example, may reveal the presence of the diphtheria bacillus; examination of the spu­tum may show the tubercle bacillus.

The direct identification of infecting agent being impossible, the serologic method is used. The latter depends upon the demonstration in the patient's serum of antibodies specific to the suspected disease. Special serologic tests have been devised for demonstrating the presence of these antibodies. Among these are hemagglutination (inhibition), complement fixation, antibody neutralizing, hemadsorption in­hibition, and precipitation test. The method of immunofluorescence consisting of detecting specific antigens in the material studied by means of luminescent microscopy has proved of great diagnostic value. The characteristic feature of acute infectious diseases is their cyclic course.

There are clearly defined stages in the course of infectious diseases: incubation (latent period), prodromal period, invasion period, active period, period of decline, convalescence.

The maximum period of incubation (i.e., the time between the data of exposure to the disease and the beginning of clinical manifestations) of some communicable diseases, e.g., chickenpox, measles, scarlet fever; smallpox, whooping cough ranges between 7 to 21 days. In some cases an increased resistance to certain infections can be observed. The capacity possessed by the body for resisting infection is spoken of as immunity. Immunity may be natural and acquired. Natural immu­nity to certain infections may be transmitted from parent to offspring. A temporary passive immunity is transmitted from the mother to her infant both through the placental circulation and through the breast milk. Acquired immunity may follow a spontaneous attack of disease, the artificial inoculation of a modified virus, vaccine injections, and injections of antitoxic and antibacterial sera. The most significant primary preventive measure is im­munization against contagious diseases. Prophylactic meas­ures applied in early childhood and the preschool ages should be directed at combating acute childhood infections. The medical science is now armed with reliable weapons for preventing infectious diseases. The treatment of infectious disease includes the method directed against the causative agent and its toxins, as well as the microbes of the secondary complication (treatment with sera, sulfa drugs, antibiotics), and the methods which favorably influence the reactivity of the organism and the patient's emotional tone (blood transfusion, administration of blood plasma and serum, gamma globulin, physiotherapy, etc.). In addition, the complex of pathogenic therapy includes setting up a hygienic atmosphere for the patient, good care and a proper diet. The principle of pathogenic therapy being applied by the Russian pediatric institutions, the mortality from infec­tions has been reduced in our country.