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 diseaseA 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.InfectionA condition that occurs when pathogens in the body multiply and damage body cells
6 Understanding the Causes of Communicable Diseases
7 VirusesTwo of the most common communicable diseases—the cold and the flu—are caused by viruses.VirusA 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 BacteriaMost 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 BacteriaAntibiotics 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 skinFungiSingle-celled microorganisms that are larger and more complex than bacteriaProtozoaMicroorganisms that enter the body through insect bitesRickettsias
14 How Diseases SpreadDiseases 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 Spreaddirect contact with an infected personpuncture woundscontact with infected animalschildbirth
16 Indirect ContactYou don’t have to be in direct contact with a person to become infected.Indirect contact can be just as dangerous.
17 Contaminated ObjectsIf 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 VectorsPathogens are often spread by a vector. Diseases that spread this way are called vector-borne diseases.VectorAn 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 PrecautionsYou can take steps to prevent infection.A few simple practices can dramatically reduce your risk of contracting communicable diseases.
22 Taking PrecautionsIn 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 bathroomAfter handling petsBefore and after inserting contact lenses or applying makeupAfter 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.