Overview
This lecture explains the stages of infection, describing each phase from initial exposure to recovery.
Definition of Infection
- Infection is the invasion and growth of harmful microorganisms within the body.
Stages of Infection
- The infectious disease process consists of five stages: incubation, prodromal, illness, decline, and convalescence.
Incubation Period
- Time from exposure to an infectious agent until onset of symptoms.
- No signs or symptoms are present, but pathogens are replicating.
- Duration varies depending on the pathogen.
- The person is unaware of developing disease.
Prodromal Period
- Intermediate period between incubation and illness.
- Pathogens continue to multiply; symptoms first appear and are non-specific (fever, fatigue, headache).
- This stage is usually shorter than incubation.
- The person is contagious and can transmit the infection.
Period of Illness
- Symptoms become specific to the pathogen and infection type (e.g., full flu symptoms).
- High level of microbial replication and peak infection.
- Stage is highly contagious.
Period of Decline
- The immune system successfully combats the pathogens and their number decreases.
- Symptoms start to improve.
- Risk of secondary infections due to weakened immune system.
Convalescence Period
- Final stage where symptoms resolve and the person returns to normal health.
- Recovery and return to pre-illness state.
Key Terms & Definitions
- Infection — Invasion and growth of harmful microorganisms within the body.
- Incubation Period — Time from pathogen exposure to symptom onset.
- Prodromal Period — Stage with first, non-specific symptoms and pathogen multiplication.
- Period of Illness — Stage with specific, most severe symptoms; peak infection.
- Period of Decline — Symptoms decrease as immune response overcomes pathogens.
- Convalescence Period — Recovery phase; return to normal health.
Action Items / Next Steps
- Review each stage and its characteristics for upcoming exams.
- Memorize the order and main features of each infection stage.