Principles of Disease and Epidemiology

11. Define diagnosis.

12. List the basic components of the diagnostic process.

13. Define:

  • Syndrome
  • Communicable disease
  • Non-communicable disease
  • Contagious disease

14. List the two types of measures of the occurrence of disease.

15. Define and differentiate between incidence and prevalence.

16. Define:

  • Sporadic
  • Endemic
  • Epidemic
  • Pandemic

17. Define:

  • Acute
  • Chronic
  • Subacute

18. Differentiate between local and systemic infections.

19. Differentiate between primary and secondary infections.

20. Define inapparent infection.

Classifying Infectious Diseases

A patient may exhibit symptoms (subjective changes in body functions) and signs (measurable changes), which a physician uses to make a diagnosis.

A specific group of symptoms or signs that always accompanies a specific disease is called a syndrome.

Communicable diseases are transmitted directly or indirectly from one host to another.

A contagious disease is one that is easily spread from one person to another.

Noncommunicable diseases are caused by microorganisms that normally grow outside the human body and are not transmitted from one host to another.

The Occurrence of a Disease

Disease occurrence is reported by incidence and prevalence.

Diseases are classified by frequency of occurrence:

The Epidemic Incidence of AIDS in the U.S.

The Severity or Duration of a Disease

The scope of a disease can be defined as:

Herd immunity is the presence of immunity to a disease in most of the population.

The Extent of Host Involvement

A local infection affects a small area of the body; a systemic infection is spread throughout the body via the circulatory system.

A secondary infection can occur after the host is weakened from a primary infection.

An inapparent, or subclinical, infection does not cause any signs of disease in the host.