Lecture on Infectious Diseases

Introduction to Infectious Diseases

• Definition: Tissue damage or dysfunction produced by a microorganism.
• Terms:
  • Endemic: Disease existing constantly in a region (e.g., malaria in Africa, COVID-19 globally).
  • Epidemic: Outbreak in a specific region/time.
  • Pandemic: Worldwide spread.

Basic Concepts of Infection

• Infection involves harmful microbe activity in/on the host.
• Types of Pathogens: Viruses, bacteria, fungi, protozoa, nematodes, microsporidia.
• Treatment specificity (e.g., antibiotics for bacteria, antivirals for viruses).

Host-Microbe Interaction

• Immunocompetence: Ability of host to fend off microbes.
• Immunocompromised: Higher risk of infection.
• Virulence: Degree of pathogenicity of microbes.
• Toxins: Poisonous substances produced by microbes.

Portal of Entry and Infection Prevention

• Transmission-based Precautions (CDC guidelines):
  • Standard Precautions: Hand hygiene, PPE (masks, gowns, gloves), respiratory hygiene, safe injection practices.
  • Contact Precautions: For patients with diarrhea, wounds, etc.
  • Droplet Precautions: For diseases spread via droplets (e.g., masks).
  • Airborne Precautions: For diseases like TB, chickenpox (use of N95 masks).

Course of Disease and Antibiotic Resistance

• Importance of antibiotic resistance (e.g., MRSA, resistant Streptococcus pneumoniae).
• Beta-Lactam Resistance: E.g., MRSA produces beta-lactamase.
• Vancomycin Resistance: E.g., VRE (Vancomycin-resistant Enterococcus).

Specific Infectious Diseases

Contact-Related Infections

• Cellulitis: Inflammation of dermis/SQ tissue by staph bacteria.
• Impetigo: Contagious skin infection, common in children.

Toxin-Related Diseases

• Botulism: Caused by toxin from Clostridium botulinum, leads to paralysis.
• Tetanus: Caused by Clostridium tetani, leads to muscle spasms (lockjaw).

Vector-Borne Diseases

• Rabies: Viral infection from animal bites, causes encephalitis.
• Malaria: Protozoal infection from mosquitoes, affects liver and RBCs.
• Zika: Viral infection from mosquitoes, mild symptoms but severe birth defects.

Respiratory Infections

• Strep Throat: Caused by Streptococcus, potential for scarlet fever.
• Diphtheria: Bacterial infection, causes throat pseudomembrane.
• Pertussis (Whooping Cough): Highly contagious, severe cough.
• Measles (Rubeola): Virus, causes dense rash, can lead to encephalitis.
• Rubella: Milder virus, dangerous for pregnant women due to fetal risks.

Herpetic Diseases

• Chickenpox (Varicella): Contagious virus causing itchy blisters.
• Shingles (Herpes Zoster): Reactivation of chickenpox virus, painful rash.
• Smallpox (Variola): Eradicated but highly contagious, serious disease.

Gastrointestinal Infections

• Infectious Diarrhea: Oral-fecal route transmission, varies in severity.
• Dysentery: Severe, bloody diarrhea caused by Shigella or amoebas.
• Giardiasis: Protozoal infection causing greasy diarrhea.
• Antibiotic-associated Diarrhea (C. diff): Inflammation due to antibiotic use, requires specific treatment.

Conclusion

• Importance of understanding infection types, transmission, and prevention.
• Emphasis on consistent hand hygiene and appropriate use of antibiotics.