Microbes and Your Health
Many illnesses are caused by
microbes which are too small to
Viruses and Bacteria
see without a microscope. Agents that cause disease are called pathogens. (pathos-suffering; )
Many of these diseases can be infectious illnesses or contagions because they pass from one
organism to another. Infectious diseases can spread through contact with an infected person, a
contaminated object, an infected animal, or an environmental source.
The four major groups of human pathogens are bacteria, fungi, protists and viruses.
Some bacterial pathogens damage body cells directly. Strep throat, for example, is caused by a
bacterium that invades cells in your throat. Other bacterial pathogens produce a poison, or toxin,
that damages cells. Some diseases caused by bacteria are tuberculosis, anthrax, gonorrhea,
bacterial pneumonia, cholera, food poisoning-salmonella and botulism, leprosy, typhoid fever,
stomach ulcers and dental cavities.
Fungi and protists may also be pathogens. Athlete's foot is caused by a fungus. The tropical
disease malaria is caused by the protist, plasmodium, that develops in the gut of
a mosquito who transfers it to a human through its saliva when it bites him. The
mosquito is a vector of the disease malaria. A vector is an organism that carries
disease-causing organisms from one host to another. The protist is a parasite
that lives in the host .African sleeping sickness is another disease caused by a
protist, trypanosoma, which is injected into a host by a vector- the tsetse fly. The
Vectors
parasite protist kills red blood cells making a person always tired.
Viruses are non-living tiny particles, much smaller than
bacteria. Viruses cannot reproduce unless they are inside living cells.
When viruses infect cells, cells are damaged or destroyed in the
process. The damaged cells release new viruses to infect other cells.
Viral diseases include HIV, SARS, measles, chicken pox, herpes,
influenza, polio and some cancers. HIV is transmitted through a
Chicken pox
carrier, a person who has the disease and may not even be showing the symptoms of illness.
Pathogens need food and a place to live and reproduce. Sometimes a human body is a
suitable place for a pathogen to meet its needs. Sources of pathogens include (1) human beings; (2)
soil, food, and water; (3) objects; and (4) animals. Some viruses and bacteria can survive outside a
person's body. They can then be spread by objects or in contaminated food or water. If you touch
an object that an infected person has sneezed or coughed on, you may transfer some viruses like
the flu, or bacteria to yourself when you touch your mouth or eyes. If you drink water or eat food
that an infected person has contaminated, you may get sick.
Animal bites can transmit some serious infectious diseases
to humans. Rabies, a virus often found in raccoons, can be
spread through the bite of an infected animal like a raccoon. Bites
from ticks can spread the bacteria that cause Lyme disease.
Bites from mosquitoes can spread the virus that causes
encephalitis.
Some viruses and bacteria live in food, water, and soil, or on
the surface of objects. The places where they are naturally found
Rabies
are environmental sources of disease. A soil bacterium called
Clostridium tetani, can enter a person's body through a wound. It produces a poison known as a
toxin, which can cause the deadly disease tetanus.
Fortunately, many bacterial diseases can be cured with medications known as antibiotics. An
antibiotic is a chemical that can kill bacteria without harming a person's cells. Antibiotics are less
effective today than they once were because many bacteria have become resistant to antibiotics.
Antibiotic resistance results when some bacteria are able to survive in the presence of an antibiotic.
Unlike bacterial diseases, there are currently no medications that can cure viral infections. For most
infectious diseases, however, the best treatment is bed rest. However, there are many over-thecounter medications that treat the disease's symptoms.
Besides using antibiotics to fight infectious disease from bacteria, we can also prevent the
spreading of the disease by using antimicrobial substance, An antimicrobial substance is one that kills
or inhibits the growth of microbes. Disinfectants are antimicrobial substances used on non-living objects.
while antiseptics are antimicrobial substances that are applied to living tissue/skin. Examples are iodine,
alcohol, hydrogen peroxide, and hand sanitizers. Bleach and formaldehyde are two examples of
disinfectants.
One way to prevent the spread of infectious diseases is vaccines. Vaccines are important tools
that help prevent the spread of infectious diseases. A vaccine is a substance introduced into the
body to stimulate the production of chemicals that destroy specific viruses or bacteria. It may be
made from dead or altered viruses or bacteria. The altered viruses or bacteria put the body "on
alert." If the virus or bacterium ever enters the body, it is destroyed before it can produce disease.
Vaccines ate typically given for measles, mumps, rubella, and the flu.
The best way to protect against infectious diseases is to stay healthy. You should eat nutritious food
and get plenty of rest, fluids, and exercise . Wash your hands often.
.
Name_________________________
Microbes and your Health
1. Why is a microbe called a microbe? _______________________________________________________
2. What is a pathogen? _______________________________________________________________________
3. What is a contagion? ____________________________________________________________________
________________________________________________________________________________________
4. Complete this concept map to show how infectious diseases can spread.
Infectious diseases
spread by contact with
4. List 4 major groups of human pathogens.
___________________________________________________________________________________
5. Give some examples of diseases caused by bacterial pathogens _________________________________
________________________________________________________________________________________
6. True or False? Fungi are not pathogens.
7. What is a vector? Give an example.________________________________________________________
________________________________________________________________________________________
8. True or False? Viruses are considered non-living because they cannot reproduce themselves.
9. True or False? The flu is spread only by direct contact, such as kissing a person with the flu.
10. What is a carrier? ____________________________________________________________________
_____________________________________________________________________________________
11. Give one example of how objects can spread diseases.
________________________________________________________________________
________________________________________________________________________
Match the animal with the disease it spreads.
Disease
Animal
_______ 12. rabies
a. ticks
______ 13. Lyme disease
b. raccoons
_______ 14. encephalitis
c. mosquitoes
15. True or False? Some viruses and bacteria that live in food, water and soil can cause disease.
16. What is the name of the bacteria that can cause tetanus and how does it infect you?
________________________________________________________________________
________________________________________________________________________
17. What is an antibiotic?
________________________________________________________________________
18. Why are antibiotics less effective now than they once were? ________________________________
_________________________________________________________________________________
19. True or False? Diseases caused by viruses can be cured with antibiotics.
20. What are liquids and other substance tat are used to kill microbes on living tissue like your skin?
__________________________________ Give an example. __________________________
21. What do you call an antimicrobial substance that is used on non-living surfaces?
______________________________________ Give and example. _____________________
22.True or False? A vaccine activates the body's natural defenses so that the body is ready to destroy an
invading virus or bacterium.
23. What are three diseases that vaccines can protect you from?
_____________________________________________________________________
24. Circle the letter of each sentence that is true about protecting yourself from infectious diseases.
a.
b.
c.
d.
Eat nutritious food.
Get plenty of rest, fluids, and exercise.
Share eating utensils or cups.
Get vaccinated.
Think!
25. Why is it important to know whether your sore throat is caused by a virus or bacteria?
________________________________________________________________________________
________________________________________________________________________________
Name_________________________
Viruses, Bacteria, and Your Health
Understanding Main Ideas Complete the table below by naming examples of behaviors to avoid, and
behaviors to practice in order to prevent the spread of infectious diseases.
What Can You Do to Prevent Catching an Infectious Disease?
How Disease Is Spread
DO NOT
DO
Contact with Infected
Person
Contact with Infected
Object
Contact with Infected
Animal
Environmental Source
Answer the following questions.
1.Why is it important to know whether your sore throat is caused by a virus or bacteria?
________________________________________________________________________________
________________________________________________________________________________
2.How do antibiotics work, and why are they becoming less effective?
__________________________________________________________________________________
__________________________________________________________________________________
3.How can a vaccine help prevent an infectious disease?
___________________________________________________________________________________
____________________________________________________________________________________
Building Vocabulary
From the list below, choose the term that best completes each sentence.
infectious diseases
vaccine
antibiotic resistance
toxin
antibiotic
4.Dead or altered viruses or bacteria that are used to stimulate the body to be "on alert" are called
a(n) ____________________________.
5. Illnesses that pass from one organism to another are called ______________________________.
6.Chemicals made by microorganisms that are used to kill bacteria are Called a(n) ___________________
7.A poisonous substance produced by bacteria is called a(n) ____________________________
8. _________________________results when some bacteria are able to survive in the presence of an antibiotic.