Infections and Immune Function Overview

Learning Objectives

  • Identify factors associated with impaired/weakened and strengthened immune function.
  • Explain the effects of both acute and chronic stress on immune function.
  • Define criteria necessary for an infection to occur.
  • Describe the stages of infection.
  • Discuss signs, symptoms, and treatment options for respiratory, gastrointestinal, and central nervous system infections.
  • Identify warning signs for seeking prompt medical attention.

Immune Function Factors

  • Risk Factors for Infection:
    • Age
    • Overcrowded, impoverished living conditions, and lack of clean drinking water
    • Frequent contact with small children
    • Exposure to immunosuppressive agents
    • Undergoing surgical procedure or physical trauma
    • Immunodeficiency disorders
    • Malnutrition
    • Tobacco smoke
    • Chronic stress overload
    • Sleep deprivation

Psychoneuroimmunology

  • Study of interactions among the nervous, endocrine, and immune systems.
  • Key Points:
    • Thoughts and emotions can modulate immune system function.
    • Immune chemicals also affect the brain.
    • Acute stress can stimulate immune function, whereas chronic stress impairs it.

Maximizing Protective Factors

  • Eat well
  • Stay up to date on immunizations
  • Stay physically active
  • Spend time outdoors
  • Wash your hands
  • Drink water
  • Maintain social connections

Infection and Infestation

  • Infection: Process where microorganisms invade bodily tissues to reproduce and cause disease.
  • Infestation: Parasitic organisms invade and live off their host’s resources.
  • Microorganisms include bacteria, viruses, and protozoa:
    • Bacteria: Single cell organisms treated with antibiotics.
    • Virus: Cannot reproduce outside a host cell; treated with antivirals or symptom management.

Transmission of Infectious Diseases

  • Infectious diseases are illnesses from infectious organisms.
  • Communicable diseases: transmitted from person-to-person, also known as contagious diseases.
  • Epidemic: Widespread occurrence of disease; Pandemic: global outbreak.
  • Flatten the curve: Reduce sharp increases in cases through preventative actions.

Conditions for Infection

  • Host must be susceptible.
  • Microbe must be capable of causing disease.
  • Microbe requires a reservoir.
    • Horizontal transmission: Person-to-person.
    • Vertical transmission: From pregnant woman to fetus.
  • Requires a route of transmission and portal of entry and exit.

Stages of Infection

  1. Incubation Period: Symptomless stage.
  2. Prodromal Period: Slight discomfort, initial symptoms.
  3. Period of Illness: Significant symptoms present.
  4. Period of Decline: Health improving.
  5. Convalescence Period: Recovery phase.
  • Severity depends on virulence, immune response, and body's recuperative power.

Respiratory Infections

  • Categorized into upper and lower respiratory infections:
    • Upper: Affects areas above neck (nose, sinuses, etc.).
    • Lower: Involves bronchi, bronchioles, and alveoli.
Common Cold
  • Acute, self-limiting upper respiratory infection caused by viruses.
  • Symptoms include runny nose, cough, fatigue. Usually resolves in a week without needing medical attention.
Influenza (Flu)
  • Viral infection affecting both upper and lower respiratory tract.
  • Types of Influenza:
    • Influenza A: Severe outbreaks, often pandemic.
    • Influenza B: Milder seasonal outbreaks.
    • Influenza C: Causes mild respiratory illness.
  • Approximately 36 million cases and around 25,000 deaths in the U.S. annually.
COVID-19
  • Caused by SARS-CoV-2, part of the coronavirus family.
  • Transmitted through close contact and contaminated surfaces.
  • Symptoms range from fever and cough to severe respiratory issues and organ system complications.

Gastrointestinal Infections

  • Gastroenteritis: Inflammation of the stomach and intestines, symptoms include nausea and diarrhea.
  • Hepatitis types explained:
    • Hepatitis A: Mild, vaccine-preventable.
    • Hepatitis B: Transmitted via bodily fluids, vaccine-preventable.
    • Hepatitis C: Chronic disease via blood exposure.
    • Hepatitis D: Requires co-infection with Hepatitis B.
    • Hepatitis E: Causes acute infection but rarely chronic.

Central Nervous System Infections

  • Meningitis: Infection of protective membranes and spinal fluid in CNS. Symptoms include fever, headache, and confusion.

Key Takeaways

  1. Many factors can weaken immune function; healthy habits can safeguard it.
  2. For infections to occur, the host must be vulnerable, and the microbe needs virulence and a transmission method.
  3. Respiratory viruses like the common cold and influenza evolve rapidly, which complicates immunity development.