1. What You Should Know Chapter 12.1
Infectious Disease
What You Should Know
Chapter 12.1

2. Infectious Disease
Diseases caused by microorganisms living in or on humans, animals, or plants.
Microorganisms also known as Pathogens
Pathogenic microorganisms include certain bacteria, viruses, fungi, protozoa, and worms.
Infectious diseases are also called… Communicable Disease – pathogens are transmitted from one living thing to another.

3. Signs and Symptoms
The presence of a disease is detected by observing signs or symptoms.
SIGNS – Objective evidence of disease that can be outwardly observed or measured: fever, pulse, skin color, breathing rate.
SYMPTOMS – subjective evidence for a disease because the evidence is based on feeling instead of outwardly measurable indicators of illness.

4. Predictable Course of Infections
Incubation Period – the time between the pathogen’s entrance into the body and the first appearance of symptoms.
Mild to no symptoms
Still contagious
Possible of spreading
Clinical Stage - Signs and symptoms of a disease arise and are most prominent.
Toxins produced
Immune response reaches it’s height
Convalescent Stage – signs and symptoms of a disease fade and a person is no longer contagious.

5. Bacteria
Single-celled organisms living in nearly every possible place that cans sustain life.
Most are helpful – large amounts live on the body’s surface and in the digestive tract.
Examples of bacteria – E. coli, Staph infections, MRSA, pneumonia.

6. Virus
A pathogen that infects cells and uses their enegy because it cannot reproduce or grow on its own.
Entirely dependent on other cells. Uses the cells resources and energy for growth.
Scientist do not consider viruses to be living organisms.

7. Fungi
Much more complex than bacteria and viruses. Built from larger cells.
Few fungi cause disease and many are beneficial. Penicillin (a life-saving drug) is made from the mold penicillium notatum.
Few fungi cause disease in humans… Mycosis is a fungal infection that usually attacks damaged tissues or weakened people.

8. Parasites
Parasites – an organism that must live inside or on another living thing, where they cause damage and disease.
Protozoa – single celled organisms that are larger and more complex than bacteria, and which may cause disease.
Worms – multicellular organisms with specialized tissues and organs that can be transmitted to humans in water or food that has been contaminated.