Download Causes of Disease

Causes of Disease
Chapter 16
Section 1
Objectives
Identify five common types of pathogen
 Describe three ways infectious disseases
are spread
 Distinguish between infectious diseases
and communicable diseases
 Identify two causes of non-infectious
diseases

Key Terms
Pathogen
 Infectious disease
 Infection
 Toxin
 Communicable disease
 AIDS
 HIV

Infectious Diseases
•
•
•
Caused by a pathogen
The pathogen invades the body and
begins to reproduce
There are five important pathogens
– Bacteria
– Protozoa
– Fungi
– Worms
– Viruses
Bacteria
Simple single celled organisms
 They live everywhere

◦ On every surface
◦ Including the inside and outside of your body

They are microscopic
◦ Cannot be seen without “help”

Some are harmful, but some are helpful
◦ Toxins result from harmful bacteria
Protozoa
Single celled organisms
 Microscopic, but larger than bacteria
 Found in most water supplies

◦ Not bottled or filtered water
◦ Most are not dangerous
Fungi
Molds and mushrooms are the most
common examples of Fungi
 Many are beneficial to humans
 Some are pathogens

◦ Athlete’s Foot
◦ Ringworm
◦ Thrush
Worms
Worms can enter the body in a variety of
ways
 They are usually immature when they enter
 They move to specific tissues or organs as
they mature
 Pathogenic worms

◦ From the environment
 Hookworms from the soil
◦ From food
 Trichina from raw or undercooked meats
Viruses
Much smaller that most bacteria
 A virus is not a cell based organism

◦ It is made of a protein coat
◦ It contains a type of genetic material

They only reproduce inside other cells
◦ It takes over the cell
◦ Destroys the cell
◦ Infects nearby cells
More about Infectious Disease
The ability of one person or organism to
transfer the infection to another person
or organism describes a communicable
disease
 Some diseases do not transfer well from
one individual to another
 A highly infectious disease may stay in one
kind of organism

◦ “bird flu” found in poultry
◦ Not HIV, found in several types of organism
AIDS
AIDS is a communicable disease caused
by a virus
 AIDS is caused by HIV
 It is possible to test for AIDS
 There are treatments, but as yet no cure
for AIDS


See page 522, Table 16.1 to see methods of disease transmission
Non-Infectious Diseases
NOT caused by pathogens
 NOT communicable
 These diseases may be inherited

◦ Muscular dystrophy, sickle cell anemia, cancer

These diseases may be caused by the
environment or exposure to toxins
◦ Cancer, heart diseases, arthritis
Summary

Infectious diseases are caused by pathogens
◦ Bacteria, protozoa, fungi, worms, and viruses
Pathogens invade the body, reproduce,
causing an infection
 Communicable diseases are infectious
diseases that can be spread from person to
person
 Non-infectious diseases are NOT caused by
pathogens, but by genetic factors, the
environment, or both

Definitions
Pathogen is a virus or microorganism that
causes disease
 Infectious disease is an illness caused by a
pathogen
 Infection is the invasion and multiplication
of pathogens in the body
 Toxin is a poisonous substance

Definitions
Communicable disease is an infection that
can be spread from person to person
 AIDS, (acquired immuno-deficiency
syndrome) is a viral disease that destroys
the body’s ability to resist other diseases
by disrupting the immune system
 HIV, human immuno-deficiency virus) is
the virus that causes AIDS
