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. 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.

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

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by direct examination under the microscope of the patient's blood, urine, stools, sputum or any patholog­ical material withdrawn from the body.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. 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.

Incubation periodmeans the interval between exposure to an infection and the appearance of the first symptoms. Prodromal period – a period of time between the appearance of the first symptoms of an infectious disease and the development of a rash or fever (a period of precursors). Invasion period – a beginning of a disease (an attack of a disease). Active period – a course of a disease with some symptoms and signs. A period of decline - decrease in strength, a gradual and continuous loss of strength of a disease. Convalescence - a recovery period.

There are some characteristic symptoms of infectious diseases.

Since infection by inhalation is common, symptoms referable to the respiratory tract are frequent. The commonest are: sore throat, coryza (running nose and eyes) and cough. Many diseases begin with one or more of these; but sore throat is particularly a feature of such diseases as scarlet fever and diphtheria; coryza appears in the common cold, measles and rubella; and cough in whooping cough and measles.

Certain common groupings of prodromal and local symptoms occur, of which headache, vomiting and sore throat are an example.

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Дата добавления: 2015-07-14