Chapter 12
Infectious Diseases
Lesson 12.1 Infectious Diseases: What You
Should Know
Lesson 12.2 Transmission, Treatment, and
Prevention of Infectious Diseases
Lesson 12.3 Immunity to Infection
Tuesday, October 20
Lesson 12.1
Infectious Diseases:
What You Should Know
Warm-Up
Infectious Diseases
What are some causes of
infectious diseases?
How are infectious
diseases transmitted?
What are some ways of
treating infectious
diseases?
Courtesy of the Centers for Disease Control and Prevention
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VIDEO
• VIDEO: Protection from Infection
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Infectious Disease Vocabulary
• Germ Theory: a scientific concept stating that
specific microorganisms cause specific diseases.
• Infectious Diseases: are caused by
microorganisms living in or on humans, animals,
or plants.
• Pathogens: Microorganisms that cause disease.
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Infectious Diseases
• Caused by microorganisms
(pathogens) living in or on
humans, animals, or plants
• Also called communicable
diseases because they can
be transmitted from one
living thing to another
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Signs and Symptoms of Disease
• Signs are evidence of
disease that can be
outwardly observed or
measured
– Fever
– An abnormal pulse
• Symptoms are evidence
of disease sensed by
the sick person
– Pain
– Shortness of breath
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Lesson 12.1 Signs and Symptoms
• For each medical scenario presented on the
handout, differentiate between the signs and
symptoms for each patient. If a patient does not
exhibit either signs or symptoms, write “N/A” in the
appropriate column.
• Work individually to complete the worksheet.
• We will discuss the answers in 10 minutes!
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Thursday, October 22 “A” Day
TODAYS AGENDA
• Infectious Diseases: What you should know
• Transmission, Treatment and Prevention of Infectious Diseases
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How Do Infections Cause Illness?
• After pathogens enter the
body, they grow,
reproduce, and produce
toxins
• Toxins cause the familiar
symptoms and signs of
illness
– Pain
– Inflammation
– Headache
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Think Further
Infections often follow stages in a recognizable
pattern. What are the three common stages of
an infection?
– The incubation period is the time between the
pathogen’s entrance into the body and the first
appearance of symptoms.
– In the clinical stage, signs and symptoms of a
disease arise and are most prominent.
– In the convalescent stage, signs and symptoms of a
disease fade and a person is no longer contagious.
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Profile of an Infection: Strep Throat
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Microorganisms
• Include bacteria, viruses,
fungi, and parasites
• Are found everywhere
and are typically invisible
to the naked eye
• Are diverse, specialized,
and sophisticated
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Bacteria
• Single-celled organisms
• Most are helpful and few
of them cause disease
• Most bacteria can grow
independently outside of
your cells
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Viruses
• Pathogens that infect cells
• Cannot reproduce or grow
on their own
• Very small, cannot be
seen with ordinary
microscopes
• Cause the common cold
and other illnesses
http://safeshare.tv/v/ss5627bfd54ab81
Ebola Virus
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Critical Thinking
Viruses
Everyone knows about the common cold and
influenza, which are notorious viral diseases.
What are some lesser known but important
viral diseases?
Chickenpox.
Flu (influenza)
Herpes.
Human immunodeficiency virus (HIV/AIDS)
Human papillomavirus (HPV)
Infectious mononucleosis.
Mumps, measles and rubella.
Shingles.
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Fungi
• Fungi include
mushrooms, molds,
and yeast
• Few fungi cause
disease and many
are beneficial
• A fungal infection,
such as athlete’s
foot, is called a
mycosis
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Parasites: Protozoa and Worms
• Parasites are
organisms that must
live inside or on
another living thing
• They cause damage
and disease
• Parasitic worms and
protozoa infect a
great number of
people
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Protozoa
• Protozoa are singlecelled organisms
• Certain protozoa
cause diseases
– Malaria
– Dysentery
– Diarrhea
Courtesy of the Centers for Disease Control and Prevention
Mosquitoes play a part in
transmitting malaria.
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Worms
• Parasitic worms are
multicellular organisms
with specialized tissues
and organs
• Methods of transmission
– In water or food that has
been contaminated with
human waste
– In undercooked meat and
fish
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Lesson 12.1 Key Concepts Review
• Complete the review worksheet and turn in to Mr.
Nolan.
• Work quietly at your table when you finish the
review worksheet.
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Lesson 12.2
Transmission, Treatment,
and Prevention of
Infectious Diseases
Methods of Transmission
• A method of transmission
is simply the way a
disease gets from one
organism to another
• Methods of transmission
are classified as either
direct or indirect
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Direct Transmission
• The exchange of
infectious material
from its origin to a
susceptible individual
• Direct contact
– Sexually transmitted
infections
– Skin infections
• Droplet spread
– Sneezing
– Coughing
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Infected People
• Many infectious diseases are spread through some
form of contact with a person who has the disease.
• The contact may be direct physical contact.
• Infectious diseases
can also spread
through indirect
contact.
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Indirect Transmission
• The exchange of
infectious material to a
susceptible person by a
source that acts solely as
a carrier
– By animals
– By contaminated objects
– By airborne means
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Contaminated Objects
• Some pathogens can survive for a period of time
outside a person’s body.
• These pathogens can be spread from person to
person on objects such as
• doorknobs
• eating utensils
• towels
• needles used for
body piercings
and tattoos
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Contaminated Food, Soil, or Water
• Some pathogens are naturally
present in food and soil.
• Sometimes water and food
become contaminated with
pathogens from infected people.
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Think Further
What are some diseases that could be
spread through contaminated water?
–
–
–
–
–
E. coli
Hepatitis
Typhoid
Cholera
Other parasitic infections
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Occurrence of Infectious Disease
• Diseases and other infections follow patterns
• An epidemic infection occurs in unexpectedly
large numbers
• A pandemic infection affects an enormous
number of people and spreads to much of the
world
• An endemic infection naturally occurs at low
levels in a particular area
• Emerging infectious diseases are new or
increasing unexpectedly
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Prevention of Infectious Diseases
• Effective preventive
measures can reduce the
incidence of infectious
diseases
• Doctors recommend
covering your nose and
mouth with a tissue when
coughing or sneezing
• Vaccination can help stop
the spread of an
infectious disease
http://safeshare.tv/v/ss5627c1dfe1115
How Vaccinations Work
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Think Further
Myth or Fact?
Hand washing is not really important in
preventing the spread of infectious diseases.
MYTH
– Fact: Hand washing reduces the occurrence of
infectious diseases that are transmitted by
respiratory droplets, blood, or direct skin contact.
– Fact: Alcohol-based hand rubs are very effective
when soap and water are unavailable.
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Food Sanitation
• Used to prevent
contamination during
food processing,
storage, and preparation
– Avoid nonpasteurized
drinks
– Refrigerate and freeze
perishables
– Cook meat thoroughly
– Wash vegetables and
fruits
– Use safe drinking water
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Treating Bacterial Infections
• Antibiotics are
substances that target
and kill many kinds of
pathogenic bacteria
• Most antibiotics are
prescription medications
• A few antibiotics can be
purchased at drugstores
without a doctor’s
prescription
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Critical Thinking
Antibiotic Resistance
Several strains of bacteria have developed
antibiotic resistance and cannot be killed by
antibiotics.
What are some steps that can help prevent
antibiotic resistance?
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Treating Viral Infections
• There are few treatments
for viral infections
• Most medications target
the symptoms and do not
attack the virus
• Medications can help
keep the virus under
control while the body
fights the infection
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Lesson 12.3
Immunity to Infection
The First Line of Defense
• The immune system
continually defends the
body against infection
• The body’s skin
(integumentary system)
forms a nearly impenetrable
barrier to pathogens
• The body’s inner surfaces
also have protection in the
form of mucous membranes
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Other System Defenses
Helpful bacteria occupy the
large intestine and inhibit the
growth of pathogens.
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• The respiratory system
is protected by mucus
• In the digestive system,
mucus coats the throat,
esophagus, stomach,
intestines, and rectum
• The regular flow of urine
flushes microorganisms
from the urinary system
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The Second Line of Defense
• A phagocyte is a white
blood cell that destroys
microorganisms
• Inflammation prepares
the body to control and
remove pathogens
• Fever stimulates
phagocytes and other
white blood cells
important for immunity
Body Scientific International, LLC.
Click here for the “Events of
Phagocytosis” animation
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The Third Line of Defense
• The third defense system is made up of specialized
cells and chemicals
• T cells reside in the blood, lymph nodes, and spleen
• A T-helper cell coordinates and
stimulates the immune response
• The T-cytotoxic cell attacks and
kills cells in your body that have
been infected with viruses
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Critical Thinking
Promoting Resistance to Infection
Resistance to infectious diseases depends on a
healthy immune system and a healthy body.
What are some steps that you can take to promote
good health?
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B Cells and Antibodies
• B cells also reside in the
blood, lymph nodes,
and spleen, where they
make special chemicals
called antibodies
• An antibody sticks to a
pathogen, labeling it as
foreign to the body
• This makes it easier for
phagocytes to find and
engulf the pathogens
Body Scientific International, LLC.
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Immune System “Memory”
• The B cells and T cells of the immune system
remember encounters with pathogens
• They can respond quickly to later exposures to
these same pathogens
• The immune response to later encounters can be
so strong that you may not become ill at all
• The immune system benefits from good nutrition
and exercise
• Some lifestyle choices, such as smoking, can
suppress immunity
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Your Immune System: Natural Born
Killer
• http://safeshare.tv/w/OZFRLSljvH
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Monday, May 4 “C” Day
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