How Pathogens Are Spread

1
How Pathogens Are Spread
- Infectious Disease

• Pathogens can spread through contact with an
  infected person soil, food, or water a
  contaminated object or an infected animal.

2
Using Prior Knowledge
- Infectious Disease

• Before you read, look at the section headings and
  visuals to see what this section is about. Then
  write what you know about infectious diseases in
  a graphic organizer like the one below. As you
  read, write what you learn.

What You Know

1. Bacteria and viruses can cause disease.

What You Learned

1. Pathogens spread through contact with an infected
   person, animal, or object, or through
   contaminated soil, food, or drink.

3
The Immune System
- The Bodys Defenses

• The immune system includes T cells and B cells.
  The cells work together to fight infections.

4
Building Vocabulary
- The Bodys Defenses

• After you read the section, reread the paragraphs
  that contain definitions of Key Terms. Use the
  information you have learned to write a
  definition of each Key Term in your own words.

Key Terms
Examples
inflammatory response
When body cells are damaged, they release
chemicals that trigger the inflammatory response,
which is the bodys second line of defense.
A major function of T cells is to identify
pathogens and distinguish one kind of pathogen
from another.
Acquired immunodeficiency syndrome, or AIDS, is a
disease caused by a virus that attacks the immune
system.
Antigens are molecules that the immune system
recognizes either as part of your body or as
coming from outside your body.
phagocyte
A phagocyte is a white blood cell that engulfs
pathogens and destroys them by breaking them down.
The virus that causes AIDS is called the human
immunodeficiency virus, or HIV.
immune response
If a pathogen infection is severe enough to cause
a fever, it triggers the bodys third line of
defensethe immune response.
The lymphocytes called B cells produce proteins
that help destroy pathogens.
lymphocyte
The white blood cells that distinguish between
different kinds of pathogens are called
lymphocytes.
These proteins are called antibodies.