Disease Periods and Classifications

Stages of Disease

1. Incubation period - Interval between the initial infection and the first appearance of any sign or symptoms

2. Prodromal Period – The onset of mild, non-specific symptoms before the full illness develops

3. Period of Illness – The stage where disease symptoms are most severe and clearly identifiable.

4. Period of Decline – Symptoms begin to subside as the immune system or treatment controls the infection

5. Period of Convalescence – The body recovers, repairs damage, and returns to a normal state

Classification of Disease Based on Extent of Host Involvement

• Local Infection: Invading microorganisms are confined to a relatively small area of the body.

  • Example: Boils and abscesses.

• Systemic Infection: Microorganisms and their products spread throughout the body via blood or lymph.

  • Example: Measles.

• Focal Infection: Agent of local infection spreads to other parts of the body where it is contained.

• Primary Infection: Acute infection that causes the initial illness.

• Secondary Infection: Infection caused by an opportunistic pathogen after the primary infection has weakened the body's defenses.

• Subclinical Infection: An infection that does not cause any noticeable illness.