1. Learning about communicable diseases and how they spread can help you prevent them.

2. communicable disease
pathogens
infection
virus
bacteria
toxins
vector

3. Understanding the Causes of Communicable Diseases
Communicable diseases are caused by several kinds of microorganisms.
If you have ever “caught” an illness from someone before, you contracted a communicable disease.

4. Understanding the Causes of Communicable Diseases
Communicable diseases, also known as contagious and infectious diseases, occur when pathogens enter your body.
Communicable disease
A disease that is spread from one living organism to another or through the environment

5. Understanding the Causes of Communicable Diseases
If your body does not fight off the invaders quickly and successfully, you develop an infection.
Infection
A condition that occurs when pathogens in the body multiply and damage body cells

6. Understanding the Causes of Communicable Diseases

7. Viruses
Two of the most common communicable diseases—the cold and the flu—are caused by viruses.
Virus
A piece of genetic material surrounded by a protein coat

8. Viruses A virus invades living cells. The virus begins to multiply.
The virus starts taking over other cells.
Disease sets in.
The body’s immune system jumps into action.
Usually, the virus is killed by the immune system.

9. Bacteria live almost everywhere on earth.
Single-celled microorganisms

10. Bacteria
Most bacteria are harmless. Some are even helpful, like the ones that help you digest food.
Unfortunately, some bacteria do cause diseases.

11. Disease-causing bacteria can produce toxins.
Substances that kill cells or interfere with their functions

12. Bacteria
Antibiotics do not work against viruses.
A bacterial disease can often be treated with antibiotics. However, some bacteria have become resistant to antibiotics as they have evolved.

13. Other Pathogens Fungi Protozoa Rickettsias
Plantlike organisms that can cause diseases of the lungs, the mucous membranes, and the skin
Fungi
Single-celled microorganisms that are larger and more complex than bacteria
Protozoa
Microorganisms that enter the body through insect bites
Rickettsias

14. How Diseases Spread
Diseases can be transmitted in a variety of ways.
Knowing how diseases are transmitted is your first line of defense against them.

15. direct contact with an infected person contact with infected animals
How Pathogens Spread
direct contact with an infected person
puncture wounds
contact with infected animals
childbirth

16. Indirect Contact
You don’t have to be in direct contact with a person to become infected.
Indirect contact can be just as dangerous.

17. Contaminated Objects
If you touch a contaminated object, you could pick up pathogens.
To protect yourself, keep your hands away from your mouth, nose, and eyes, and wash your hands regularly.

18. Vectors
Pathogens are often spread by a vector. Diseases that spread this way are called vector-borne diseases.
Vector
An organism that carries and transmits pathogens to humans or other animals

19. Contaminated Food and Water
When food is improperly handled or stored, harmful bacteria can develop.
Water supplies that become contaminated with human or animal feces can also cause illnesses such as hepatitis A.

20. Airborne Transmission
When an infected person sneezes or coughs, pathogens are released into the air as tiny droplets that can travel as far as 10 feet.
Other pathogens such as fungal spores are also small enough to spread this way.

21. Taking Precautions
You can take steps to prevent infection.
A few simple practices can dramatically reduce your risk of contracting communicable diseases.

22. Taking Precautions
In Japan, people who have colds or the flu often wear masks when they go outdoors to avoid spreading communicable diseases to other people.

23. Wash Your Hands When to Wash Your Hands Before you eat
After you use the bathroom
After handling pets
Before and after inserting contact lenses or applying makeup
After touching an object handled by an infected person

24. Protect Yourself from Vectors
Limit the time you spend outdoors at dawn and dusk, when mosquitoes are most active.
Wear pants and long-sleeved shirts to avoid insect bites.
Use insect repellent, and avoid contact with dead birds.

25. Other Prevention Strategies
Avoid sharing personal items, such as eating utensils.
Handle food properly.
Eat well and exercise.
Avoid tobacco, alcohol, and other drugs.
Abstain from sexual contact.
Cover your mouth when you cough or sneeze, and wash your hands after using a tissue.

26. After You Read Reviewing Facts and Vocabulary
Define the word communicable.
Something that can be spread from person to person or through the environment

27. After You Read Reviewing Facts and Vocabulary
List three ways that communicable diseases are spread through indirect contact.
Through contaminated objects, vectors, and contaminated food and water

28. After You Read Reviewing Facts and Vocabulary
How is a virus different from bacteria?
A virus is a piece of genetic material surrounded by a protein coat, while bacteria are single-celled microorganisms that live almost everywhere on Earth.