Infectious Disease Stages, Treatments, and Immune Defenses

Stages of Infectious Disease Development

• 1. Incubation Phase: The time interval between the invasion of pathogens and the manifestation of the first symptoms.
• 2. Overt Disease Phase: The period where clear symptoms and signs of disease appear due to tissue damage.
• 3. Convalescence Phase: The recovery period after the removal of pathogens, where the body repairs damage and restores health.

Treatments for Infectious Diseases

• Serum Therapy: The introduction of antibodies against a specific microbe, produced by another person or animal, into the diseased organism.
• Chemotherapy: The administration of chemical drugs to combat microbes. These can be microbicides (destroying germs) or microbiostatic (preventing reproduction). Key examples include sulfonamides and antibiotics.

Body Defenses Against Infection

External Passive Barriers

These are the first line of defense preventing pathogen entry:

• Structural: Skin and mucous membranes covering the body surface and digestive tract.
• Mechanical: Movements like cilia in the airways that drag out foreign particles.
• Biological: Non-pathogenic microorganisms that compete with and inhibit potential pathogens.
• Biochemical: Substances in saliva, tears, gastric juices, and sebaceous gland secretions that destroy or inhibit microbes.

Internal Immune Defenses

The body uses leukocytes (white blood cells) to limit the spread of and kill microbes:

• Non-specific Defense: Acts against any microorganism or foreign particle. Phagocytes trap and kill microorganisms through phagocytosis.
• Specific Defense: Acts selectively against specific microorganisms or foreign molecules. Lymphocytes produce specialized proteins called antibodies.