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Communicable Diseases
A disease cause by and agent that can be
passed from one living thing to another.
Examples of infectious disease
 Animals spreading disease
 Bubonic Plaque- rats : fleas -B
 Lyme Disease –Deer Ticks- B
 Rabies- Dogs: Cats: Raccoons: Bats V
 Ringworm- Dogs: Cats –F
 Malaria- Mosquitoes
 Trichinosis – Worms: pigs
What Causes infectious Disease
 Pathogen – Any agent that causes disease –
 Bacteria
 Virus
 Fungi
 Parasitic worms
 Protists
These are the causes of infectious disease
 Microorganism – a living thing that can only be seen with a
microscope
How are infections spread
 Through the Air (sneezing)
 Contact with a contaminated object (doorknobs)
 Person to Person (shaking hands, kissing)
 Animals (deer – lyme disease, infected dog (ringworm,
rabies)
 Food and Water (eating contaminated food or water)
Physical and Chemical Diseases
Make up your body’s 1st line of defense against pathogens.
 Physical barriers.
 Skin
 Cilia – small hairs in respiratory system. Sweep mucus and
pathogens to the throat to be swallowed or coughed out.
 Chemical methods – destroy those invaders
 chemicals found in sweat
 Enzymes found in tears & saliva
 Gastric juice in stomach
The Immune System
network of cells, tissues, organs and chemicals that fights off pathogens.
Inflammatory response
 reaction to tissue damage caused by injury or infection.
 Prevents further injury and stops pathogens
1. In response, blood vessels expand, more blood to the area
2. Fluid and cells from the bloodstream cause swelling and pain.
Pressure on the nerve endings
3. Phagocytes, white blood cells attack invading pathogens.
1.
Pus, mass of dead white blood cells and damaged tissue may build up at the site of
inflammation to fight bacteria.
4. With pathogens killed and body repairs tissue
 Bacterial Disease – such as strep throat, sinus infections can be treated
with antibiotics
 Viral Diseases – such as the flu, chickenpox, or mononucleosis, do not
respond to antibiotics.
The Immune System (13:46)
 https://www.youtube.com/watch?v=z3M0vU3Dv8E
Fighting Disease
 Bacteria,viruses, and other agents of disease are everywhere
around us:
 Air we breath
 Surfaces we touch
 On our skin
Even if it enters your body, it cannot make you sick unless it
survives, multiplies and causes damage to your system.
Most of the time, pathogens are quickly destroyed or swept away
before they have a chance to multiply
Infection & Disease
If pathogens do enter your system and begin to spread and
reproduce, then you are infected.
 Body can still defend against them, destroy or make them
harmless (chicken pox, virus stays in your body
Disease – harmful change in your body’s normal activities
 Feel sick
 Damage to your cells and tissues
Signs & Symptoms – effects of a disease
 Something a person can see (sneezing, coughing, pale/flush skin)
 Feeling of pain or discomfort (sore throat, tiredness, nausea)
Defenses against infection
Skin
Chemical warfare on germs
 Sweat & oils contain acids that kill bacteria
 Enzymes in tears and saliva
Mucous Membranes
 Tissues lining the openings into your body (mouth and nose)
Stomach Acids
 Some pathogens might enter your system when you touch your
fingers to your lips, breathe through your mouth or bite your nails.
 Most are destroyed in your stomach
Helpful Microorganisms

bacteria live on the skin and in your mouth. Take up space and
leave not room for other pathogens.
Inflammation (swollen, red, painful)
 Phagocytes (found in white blood cells) attack, eat and destroy
any microorganisms.
Immune System
 Destroy invaders in time to prevent diseases
 bone marrow – grows white blood cells lymphocytes
 Thymus gland – incubates some lymphocytes and changes them
into T-cells (they recognize enemies) or other lymphocytes
become B Celle (they make antibodies)
Lymphocytes travel in body fluids
during infection they are drawn to lymph nodes
 T & B cells work together
 Recognize
 Fire antibodies
 Capture
 Memorize
Immunity
 Innate Immunity
 Some people seem to inherit resistance to certain human
diseases
 Active Immunity
 Once your body has launched an all-out war against a specific
invader, it remains armed and ready to fight that same invader
much more quickly and effectively.
Passive immunity
you have received antibodies from another person or sometimes
and animal that have made you resistant to disease or infection
How do immunizations work?
Common Viral Diseases
 Common cold
 Influenza
 Chickenpox
 Mononucleosis
 Hepatitis
 measles
Common Bacterial Diseases
 Strep throat (sore throat, can cause permanent heart and
kidney damage)
 Tuberculosis (attacks lungs and cause fluid to build up there)
 High fever, weakness, loss of appetite)
Sinus Infections
cold, flu, or allergy that leads to heavy mucus production can
lead to a bacterial infection in our sinuses)
Where Are The Most Bacteria-Filled Places In Your
Life?
https://www.youtube.com/watch?v=NYgvCtrdu2U
25 Bacteria Facts That Might Make You Feel Dirty
https://www.youtube.com/watch?v=Lg-1Vv4-58M
THREATS TO HUMAN HEALTH
PRESENTED BY VIRUSES
 When it was discovered that bacteria could cause disease, there were
many illnesses for which bacterial agents could not be found. These
included serious diseases such as smallpox, polio, rabies and influenza, as
well as less serious maladies such as the common cold. These diseases,
and many more, are caused by viruses.
 Viruses are infectious agents which are between 20 and 100
times smaller than bacteria. They are too small to be seen through a
normal microscope and can be visualized only by an electron
microscope. Viruses consist of strands of genetic material (RNA or
DNA) surrounded by a coating of protein (called a capsid). Viruses are
not considered to be living organisms because they cannot reproduce
outside of a living cell.
How they infect
 Viruses multiply by inserting their genetic information
into a cell and harnessing the cell machinery to
replicate the viral genetic material and make new
capsids. The new viruses are then transmitted to other cells,
either through the cell wall or when the cells burst and die.
Viruses are parasites on a cellular level.
 New strains of disease-causing viruses are a constant threat
because viruses mutate easily. For example, each year a
new influenza virus causes illness in millions of people. As a
result, and because most drugs cannot disable a virus without
harming healthy tissue, it is difficult to develop drug
therapies to cure viral infections.
Ebola
 Viruses can be transmitted from one animal species to another. They
affect each species differently and one species can harbor viruses deadly
to another without any ill effect. For example, most Ebola viruses and
the Hanta virus, do not cause disease in their host animals, but they are
deadly to man. The Ebola-Reston virus, on the other hand, is deadly to
monkeys but does not cause illness in humans.
 Viral illnesses can be spread in a number of ways. Some, such as AIDS
and Ebola, can only be spread through exchanges of blood or other
bodily fluids. Others, such as influenza and the common cold, are
airborne and enter through the respiratory tract. The Hanta virus is
spread by breathing dried rodent feces which become airborne.
Quarantine
 Quarantine deprives people of their liberty not because they
have committed any crime, but due to their exposure to a
dangerous communicable disease. The power of the state to
impose quarantines has been recognized for many hundreds
of years. In the United States, there has never, to our
knowledge, been an instance when the state was granted the
power to kill people exposed to disease. This is clearly a gross
deprivation of due process. The only way that it could be
justified is if it were a certainty that the entire country, or
large portions of it, would be wiped out unless the action
was taken. The film explores this dilemma.