Characteristics of Infectious Diseases

158

Characteristics of Infectious Diseases

Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi.

There are two main forms of the infectious process:

  1. Infectious disease
  2. Microbial carrier state (microbial carriage).

Characteristics of Infectious Diseases

Infectious disease

  • It is the clinically manifested form of the infectious process, its extreme degree of manifestation.
  • Infectious diseases comprise a great group of disorders caused by pathogenic bacteria, viruses, fungi, and protozoans.
  • Thus, infectious illness is caused by live causative agent.
  • In the majority of cases these diseases are contagious, have a latent period of a certain length and in most cases are followed by specific host response against the invaded pathogen with the production of immunity.
  • A typical infectious disease has well-defined common periods in its course.

Incubation period

  • It lasts from the moment of infection to the onset of first clinical symptoms of the disease.
  • The duration of the incubation period depends on the dose and virulence of the pathogen, immune system state and on the influence of environmental factors. It ranges from several hours (in influenza, cholera, etc.) to months and even years (hepatitis B, leprosy).
  • In some diseases, the prodromal period follows the incubation period, where the non-specific symptoms similar in many diseases are manifested (fatigue, weakness, malaise, headache, dizziness, subfebrile temperature, loss of appetite, etc.)

Period of clinical manifestations (height of the disease)

  • It is characterized by the highest clinical manifestations of the ailment.
  • The most typical features of the infectious disease height are fever, functional and organic disturbances in the affected system or organ (respiratory failure, digestive and urinary tract malfunctions, or CNS disorders).
  • This stage comes gradually to the outcome period, where the disease is usually finished by convalescence (recovery).
  • Other but unfavourable results of the infectious disease course include the development of the chronic disease, carrier state establishment, or lethal outcome.

Microbial carrier state (microbial carriage).

  • The continued presence of a pathogen that does not cause any symptoms but can transmit and infect other persons.