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Infectious Diseases

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Communicable disease is an infectious disease that is passed from one person to another. ... Contact with contaminated objects ... – PowerPoint PPT presentation

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Title: Infectious Diseases


1
Chapter 21
  • Infectious Diseases

2
21.1 What are infectious diseases?
  • One that is caused by an agent that can pass from
    one organism to another.
  • Communicable disease is an infectious disease
    that is passed from one person to another.

3
What causes infectious diseases?
  • Infectious diseases are caused by pathogens- any
    agent that causes disease.
  • In the U.S. the most common pathogens are viruses
    and bacteria.
  • Others are fungi, protists, and parasitic worms.
  • These must be seem under a microscope

4
Bacteria
  • Very simple living things
  • Each bacterium is a single cell much smaller than
    the ones that make up your body
  • Common diseases caused by bacteria are strep
    throat, food poisoning, and urinary-tract
    infections.

5
Viruses
  • A microscopic disease-causing particle consisting
    of genetic material and a protein coat.
  • Cannot reproduce without first invading a living
    cell
  • Once inside the cell the viruses genetic material
    acts as a program that directs the cell to make
    more viruses.
  • Viruses are specialized to infect only certain
    types of cells. Some diseases that animals can
    get cannot be transmitted to humans.
  • Some common diseases caused by viruses are the
    common cold, the flu, cold sores, and measles.

6
How are infectious diseases spread?
  • In order for the disease to spread to you, a
    pathogen must leave the body one living thing and
    enter your body.
  • One way this happens is through the air. This
    happens when one sick person sneezes and
    thousands of tiny drops of mucus and saliva are
    sprayed into the air.
  • Someone nearby breaths the droplets and becomes
    infected.

7
How spread, cont
  • Contact with contaminated objects
  • A sick person may leave bacteria or viruses on
    objects like doorknobs, telephones, drinking
    glasses, toothbrushes, towels, and combs.
  • Some bacteria or viruses do not live long on
    these objects and others live long enough for
    others to contract the illness.

8
How spread, cont
  • Person to person
  • Shaking hands, kissing, touching the cold sores
    of another person

9
cont
  • Animals that spread disease
  • Humans can get ringworm from handling an infected
    dog or cat
  • Possible to get rabies from the bite of an
    infected animal
  • A type of encephalitis, inflammation of the
    brain, is spread by mosquitoes
  • Lyme disease is a serious bacterial infection
    carried by ticks
  • Hantaan virus causes a deadly hemorrhagic fever
    and can be transmitted through contact with feces
    from infected rodents.

10
cont
  • Food and water
  • Usually happens when feces of an infected person
    or animal enters the water system
  • People who work with food are required by law to
    wash hands after going to the bathroom
  • Also important to wash fruits and vegetables
    thoroughly, because they are grown in fertilized
    soil. Fertilization material may contain feces.
  • Large number of bacteria in food may cause food
    poisoning
  • To keep your risk of food poisoning low, wash
    hands while cooking, avoid cross contamination,
    refrigerate leftovers right away.
  • While camping, do not drink water from lakes and
    streams without purifying it first.

11
21.2 Fighting disease
  • Infection and disease
  • If pathogens do enter your system and begin to
    spread and reproduce, then you are infected
  • Being infected is not the same as having the
    disease or being sick
  • Your body can put up a good fight against them
    and you may net even get sick
  • But you can still get someone else sick

12
disease
  • If your defenses cannot stop the pathogen quickly
    enough, you may begin to feel sick
  • A pathogen can cause disease when it is able to
    multiply in your body and cause damage to your
    cells and tissue
  • You then begin to experience symptoms of being
    sick

13
Defenses against infection
  • Your body has ways of coping with disease causing
    bacteria, viruses, and other pathogens
  • Skin- upper layers are make up of dead skin cells
    filled with a tough water-proof protein.
  • As you shed dead skin cells you also shed
    bacteria, viruses, and other pathogens on your
    skin

14
Defenses, cont
  • Chemical warfare on germs
  • Many chemical substances in your body act to
    destroy pathogens
  • Examples are sweat, oils, saliva, and tears

15
Defense, cont
  • Stomach acids
  • If a pathogen enters the body through the mouth,
    travels to the stomach, than the stomach must
    fight it.
  • Stomach acid is 10X stronger than pure lemon
    juice and can also protect your from disease and
    digest your food
  • Mucous membranes
  • Tissue linings in the openings of your body
  • Inside your mouth and nose (cilia)

16
Defense, cont
  • Inflammation
  • When you get a cut and it becomes red and
    infected, that inflammation is the bodies
    reaction to the pathogen
  • Helpful microorganisms
  • Some microorganisms and helpful and guard you
    against disease
  • Harmless bacteria lives on your skin and in your
    mouth

17
Defense, cont
  • The immune system
  • See figure 21-7 on p 448
  • All different kinds of cells launch a war on
    the pathogen and an immune response is activated.

18
Weapons of the immune response
  • Our body has many different kinds of immune cells
    waiting to do battle with pathogens that are
    trying to make us sick.
  • There are 2 main types of cells
  • T-cells and B-cells

19
T-cells
  • Mobilize to fight pathogens directly
  • These T-cells divide into many cells and attack
    the invaders
  • Helper T-cells are the first line of defense
  • Then Suppressor T-cells turn off the immune
    response after the pathogen has been defeated

20
Antibodies
  • B-cells
  • Their job is to produce antibodies
  • Y shaped molecules that stick to and cover
    foreign molecules in the body.
  • The virus or bacteria have little chance at
    attacking body cells if covered with antibodies

21
Immunity
  • Means when you have had certain diseases, you
    cannot get them again
  • Protection against developing a certain disease
    is called immunity
  • There are three basic types

22
Innate immunity
  • Immune to certain diseases just because you are
    who you are

23
Active immunity
  • Once your body has launched an all out war, your
    body is ready to fight the invader much more
    quickly next time.
  • They have memory cells that kick into gear
  • Two ways to get active immunity
  • To actually get the disease
  • To get immunized against the disease
  • A way of tricking your body into thinking it
    already had the disease

24
Passive immunity
  • You have received antibodies from another person
    or animal that have made you resistant to the
    disease
  • May get them fro your mother before birth
  • May get them from a serum of an animal if you
    have been bitten by an animal with rabies or been
    bitten by a poisonous snake.

25
21.3 common infectious diseases
  • Viral diseases
  • Colds, influenza, cold sores, warts,
    mononucleosis, chickenpox, and AIDS

26
Preventing viral diseases
  • A number of viral diseases that were common in
    the 40s and 50s are not rare
  • Polio, measles, mumps, and rubella
  • Today most children are immunized against these
    diseases
  • However measles is an exception and it is making
    a comeback and it is recommended to get immunized
    before college
  • Most deadly viral disease now is AIDS

27
Curing viral diseases
  • Antibiotics
  • Prevents the cell division and growth of living
    bacterial cells

28
Common infectious diseases
  • The common cold
  • Influenza
  • Chicken pox
  • Measles
  • Mononucleosis
  • Hepatitis
  • See chart and book for facts and figures,
    symptoms and signs, and treatment of these
    diseases

29
Common bacterial diseases
  • Strep throat
  • Tuberculosis
  • Sinus infections
  • Malaria
  • Hookworm, ringworm, tapeworm, pinworm, roundworm.
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