Detailed Notes on Infection and Disease

Introduction to Infection & Disease

  • Importance of health care and public health in society.
    • C. Everett Koop: "Health care matters to all of us some of the time; public health matters to us all of the time."

Causes of Death in 2021 (U.S.)

  • Leading Causes (age-adjusted death rate per 100,000):
    • Heart Disease: 164.7
    • Cancer: 145.4
    • COVID-19: 130.8
    • Unintentional Injuries: 85.0
    • Stroke: 38.8
    • Chronic Lower Respiratory Diseases: 32.4
    • Alzheimer’s: 30.0
    • Diabetes: 24.8
    • Chronic Liver Disease/Cirrhosis: 13.3
    • Kidney Disease: 12.7
  • NOTES:
    • 74.5% of all U.S. deaths attributed to these 10 causes.
    • Statistical significance noted in changes from 2020 to 2021.

Host-Parasite Relationships

  • Microbial Symbiosis:
    • Human body maintains balance with microflora.
    • Infection: Invasion/colonization by microorganisms.
    • Disease: Alteration of host's health due to infection.
    • Example: Streptococcus pneumoniae.
  • Pathology studies the cause and progression of diseases (like AIDS).

Contact-Invade-Infect-Disease Overview

  • Microbial Pathogenic Cycle:
    • Contact: Microbes enter body.
    • Invasion: Crossing defense barriers.
    • Infection: Microbes establish in tissues.
    • Disease: Resulting injury/disruption of tissues.

Human & Microbe Symbiosis

  • The human body houses about 100 trillion microbes (~3 lbs).
  • Microflora (resident bacteria) is established during birth.

Microbiota

  • Normal Flora:
    • Adapted to various niches in the body.
    • Majority beneficial, can cause disease if immunity is compromised.
  • Compromised immunity may lead to opportunistic infections.

Microbial Colonization by Body Regions

  • Key Regions:
    • Skin: Propionibacterium, Staphylococcus, Corynebacterium.
    • Eyes: Staphylococcus epidermidis, S. aureus.
    • Mouth: Streptococcus, Lactobacillus, Actinomyces.
    • Large Intestine: Escherichia coli, Bacteroides, Lactobacillus.
  • Comments highlight the role of moisture, nutrient availability, and antimicrobial properties of different areas in protecting against infections.

Factors of Infection & Disease

  • Pathogen Types:
    • True pathogens: cause disease in healthy individuals.
    • Opportunistic pathogens: cause disease when the host's immune system is compromised.
  • Examples of opportunistic pathogens include E. coli in UTIs.

Infection Classification

  • Portal of Entry:
    • Specific routes of entry for pathogens (e.g., respiratory, gastrointestinal).
    • Infectious dose: minimum microbes needed to cause infection.

Mechanisms of Pathogenicity

  • Modes of Action:
    • Direct damage to host cells and systematic effects from toxins (endo and exo).
  • Virulence Factors: Enable pathogen to cause disease (e.g., adherence mechanisms like fimbriae and capsids).

Epidemiology

  • Study of Disease in Populations:
    • Key Metrics:
    • Prevalence: percentage of the population affected.
    • Incidence: number of new cases in a specified time frame.
    • Classification of disease occurrence:
    • Endemic: constant presence.
    • Epidemic: sudden increase above normal.
    • Pandemic: widespread across countries.

Infection Control in Hospitals

  • Nosocomial Infections (HAIs):
    • Acquired during hospital stays, prevalent due to various risk factors.
    • Common types include urinary tract infections, surgical site infections, and lower respiratory infections.
  • Universal Precautions:
    • Methods employed to reduce transmission (e.g., sanitization, use of PPE, and isolation techniques).