1. Unit 3
Infectious Disease

2. Terms To know
Infectious Disease : disease caused by a microscopic germs that can pass from one thing to another. Some cannot pass to new individuals (i.e. Lyme disease)
Communicable Disease : an infectious disease that is passed from one person to another.
Microorganisms : a living thing that can be seen only with a microscope (Ex: bacteria, fungi, protists).
Pathogens : any agent that causes diseases.
2 most common pathogens Other Pathogens
1. Bacteria fungi
2. Viruses protists
- parasitic worms

3. Types of Bacteria (common)
Unicellular microorganism that can cause disease; majority are harmless, but some are pathogenic (1%)
Can kill bacteria with antibiotics
Binary Fission- reproduction of bacteria by splitting of the body into 2 new bodies.
Types of Bacteria (common)
Strep throat
Food/water poisoning
Urinary-tract infection
Tuberculosis
Staph Infection- MRSA (antibiotic
resistant)
Yersinia pestis
Pneumonia

4. Types of viruses (common)
A microscopic disease causing particle consisting of genetic material and a protein coat
Attacks and kills living cells to make new viruses
NO CURE
Types of viruses (common)
mononucleosis . Polio
hepatitis Measles
influenza Tetanus
cold sores (herpes simplex type 1)
Chicken pox Small Pox
Common cold Pneumonia

5. Other pathogens Fungi (mushrooms, mold, mildew)
athlete’s foot, ringworm, pneumonia
Protists (single or multi-celled organism)
Malaria, giardia infection
Parasitic Worms (multicellular organism)
tapeworm (water/meat), flatworm (water), hookworm (feces/soil), roundworm (meat)

6. How are Infectious Diseases Spread?
1. Through the air Ex: chicken pox, flu, tuberculosis
2. Contact with Contaminated Objects Ex: poison ivy
3. Person to person Ex: HIV, STDs, monucleousis
4. Food and Water Ex: salmonella, E-coli
5. Animal Spreading Diseases Ex: malaria, rabies, Lyme disease

7. External and Internal Defense (1st line of defense)
Innate Immunity- non specific defense
Physical Barrier: skin epidermis
Chemical Warfare on Germs: tears, saliva, ear wax, fever, inflammatory response
Mucus Membranes: line body cavities of respiratory, urinary, and digestive tract
Stomach Acids
Helpful Microorganisms
Phagocyte Cells (patrol the circulatory system “find and eat” unnatural cells)

8. Acquired Immunity Acquired Immunity- antigen specific defense
Active immunity- natural or artificially developed immunity.
Passive immunity- antibodies acquired from mother to child during pregnancy or injected.
Immune system – protects body from disease
Vaccination – injection of a small amount of a pathogen that will provide protection against an infectious disease (live, killed, toxoid, 2nd generation)
Antibiotics – drugs that kill or limit the growth of bacterial infections not viruses.

9. Immune System Response
Pathogens – disease causing agent breaches the external innate defense mechanisms.
Macrophage – phagocyte that engulfs pathogen using cytoplasmic extensions and ingest and digest and display it
Helper T cells – drive the immune system response; activation of B Cells and killer T Cells
Killer T cells – kills infected cells marked for destruction.
B cells – bind to antigen divides & clones. Produce antibodies and remembers the antigen.
6. Antibodies – protein that marks antigen for destruction by phagocytes & neutralizes it by blocking binding sites
7. Suppressors T cells – turns off immune system when the infection is cleared. Regulates self-tolerance (prevents body from not attacking own cells)
Memory T cells – remembers the antigen & immediately attacks (secondary immune response)