Infection Concepts and Pathophysiology

Infection Concepts

• Infection Cause: A pathogen (bacteria, virus, fungus, or parasite) enters the body and avoids the body's defenses.
• Pathogen Types:
  • Bacteria: Cause diseases like tuberculosis, pneumonia, and bacterial meningitis.
  • Viruses: Cause diseases like COVID-19, influenza, and herpes.
  • Fungi: Cause diseases like candidiasis and tinea infections.
  • Parasites: Cause diseases like malaria and giardiasis.

Pathophysiology of Infection

• Incubation Period: Time between pathogen exposure and first symptoms. Pathogens enter the host, colonize tissues, and start multiplying. Can last from hours to years (e.g., HIV latency period).
• Prodromal Stage: Initial, often mild symptoms (e.g., malaise, fatigue) as pathogens multiply and release toxins.
• Invasion (Acute Illness) Period: Pathogens rapidly multiply and spread, leading to tissue damage and triggering immune/inflammatory responses. Symptoms are related to the specific organ being targeted (e.g., cough in pneumonia).
• Convalescence: Recovery period where the immune system eliminates pathogens and repairs damaged tissue. Outcomes range from full recovery to latency (e.g., herpes simplex viruses) or chronic infection (e.g., hepatitis C).

Transmission of Infection

• Direct Transmission:
  • Person-to-person contact (touching, kissing, sexual contact).
  • Vertical transmission (mother-to-child, e.g., HIV during childbirth).
• Indirect Transmission:
  • Fomite transmission: Contact with contaminated objects.
  • Airborne transmission: Spread via droplets in the air (e.g., SARS-CoV-2).
  • Vector-borne: Spread by vectors (e.g., mosquitoes transmitting malaria).
  • Waterborne/Foodborne: Spread through contaminated water or food.
  • Zoonotic: Spread from animals to humans (e.g., Ebola, SARS-CoV).

Risk Factors for Infection

• Host Factors:
  • Age: Increased susceptibility in newborns and older adults due to weakened immune responses.
  • Immunosuppression: Weakened immune systems increase risk from drugs (e.g., corticosteroids) or diseases (e.g., HIV, cancer).
  • Comorbidities: Underlying conditions (e.g., diabetes, chronic kidney disease) increase susceptibility.
• Environmental Factors:
  • Overcrowding: High population density increases pathogenic exposure.
  • Poor hygiene/sanitation: Increases risk of waterborne/foodborne infections.
• Pathogen factors:
  • Pathogenicity: An organism's ability to cause disease.
  • Virulence: Severity of the disease an organism can cause.
  • Immune Evasion: A pathogen's ability to evade the immune response (e.g., mutation in HIV).
• Exposure factors:
  • Healthcare exposure (e.g., contaminated needles).
  • Travel history to endemic regions (e.g., exposure to Ebola in Africa).

This quiz delves into the various causes of infections, including pathogens like bacteria, viruses, fungi, and parasites. It also covers the stages of infection such as incubation, prodromal, and the acute illness period. Test your understanding of these critical concepts in infection and their impact on health.