Myth There isn’t much a person can do to avoid spreading or catching a cold or the flu.

Fact About 80% of infectious diseases are spread by hand contact. Washing your hands with soap and water is a simple and effective way to prevent the spread of colds and the flu.

Do you think most teens wash their hands as much as they should? What do you think are some ways to encourage more frequent hand washing?

•Communicable diseases, also know as infectious diseases are caused by organisms or viruses that enter and multiply within the human body.

Causes of Communicable Diseases

•Microorganisms are organisms that can be seen only through a microscope.

•Microorganisms and viruses that cause disease are called pathogens.

•Pathogens can cause an infectious disease when they enter your body and multiply.

•Bacteria (bak TEER ee uh) are simple, single-celled microorganisms. Bacteria live in air, soil, food, and in and on the bodies of plants and animals, including you.

Bacteria

•Some bacteria injure cells by giving off poisons called toxins (TAHK sinz).

•The smallest pathogens are viruses.

Viruses

•A virus can multiply only after entering a living cell.

•The virus then takes over the cell’s reproductive mechanisms, resulting in cell damage or death.

•Organisms such as yeasts, molds, and mushrooms are known as fungi (FUN jy).

Fungi

•Fungi grow best in warm, dark, moist areas.

•Single-celled organisms that are much larger and more complex than bacteria are known as protozoans (proh tuh ZOH unz).

Protozoans

•Protozoans have the ability to move through fluids in search of food.

Pathogens can spread through contact with

How Pathogens Are Spread

•an infected person•an infected animal•contaminated objects•contaminated food•contaminated soil•contaminated water

The pathogens can then enter the body through breaks in the skin or through the moist linings of the eyes, ears, nose, mouth, or other openings.

•Many infectious diseases are spread through some form of contact with a person who has the disease.

Infected People

•The contact may be direct physical contact.•Infectious diseases can

also spread through indirect contact.

Some infectious diseases are transmitted to humans through the bites of animals.

Infected Animals

•Some pathogens can survive for a period of time outside a person’s body.

Contaminated Objects

•These pathogens can be spread from person to person on objects such as

•doorknobs•eating utensils•towels•needles used for

body piercings and tattoos

•Some pathogens are naturally present in food and soil.

Contaminated Food, Soil, or Water

•Sometimes water and food become contaminated with pathogens from infected people.

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1) Saliva and tearsSaliva and tears can wash away some pathogens.

2) Mucous membranesMucus traps some pathogens, preventing them from entering your body.

3) CiliaCilia help move mucus and pathogens out of your body when you cough or sneeze.

Your Body’s Physical and Chemical Defenses

4) SkinYour skin is an effective barrier against many pathogens.

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5) Stomach acidWhen you swallow certain pathogens with food, water, or mucus, acids in your stomach can kill those pathogens.

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Health Stats Note the difference between the leading causes of death in the United States in 1900 and in 2000.

Were any of the leading causes of death in 2000 infectious diseases? Explain why you think this is the case.

• There are thousands of infectious diseases, and over 40 kinds commonly occur in the United States.

Bacterial Diseases

• Four infectious diseases caused by bacteria are

• strep throat

• Lyme disease

• meningitis

• tuberculosis

• “Strep” is short for Streptococcus, the bacterium that causes the disease.

Strep Throat

• Strep bacteria, which are usually found in the nose and throat, can be spread by contact with mucus from an infected person.

• Symptoms include

• sore throat

• swollen lymph nodes on the sides of the neck

• headache

• fever

• Humans can become infected with the bacteria that cause Lyme disease when they are bitten by an infected tick.

Lyme Disease

• Symptoms of Lyme disease include

• The best way to protect yourself from Lyme disease is by avoiding tick bites.

• a red rash at the site of the tick bite

• fever

• chills

• body aches

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• An infection of the fluid in the spinal cord and the fluid that surrounds the brain is called meningitis.

Bacterial Meningitis

• Symptoms of meningitis include high fever, headache, vomiting, and a stiff neck.

• There are two types of meningitis—one is caused by bacteria, the other by a virus.

• A highly contagious bacterial infection of the lungs is tuberculosis (too bur kyuh LOH sis), or TB.

Tuberculosis

• It is transmitted when droplets from an infected person’s cough or sneeze are inhaled.

• Symptoms, which include fatigue, weight loss, a mild fever, and a constant cough, may not show up for many years after the initial infection.

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• An antibiotic (an tih by AHT ik) is a drug that inhibits or kills bacteria.

Treating Bacterial Diseases

• Using antibiotics exactly as they are prescribed is very important to prevent bacteria from developing resistance to the medicine.

• Antibiotic resistance can result if you don’t finish your prescription and some of the bacterial pathogens in your body survive.

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Viral diseases include

Viral Diseases

• the common cold

• influenza

• pneumonia

• hepatitis

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• The common cold is really a group of symptoms that is caused by a number of different viruses.

The Common Cold

• One or two days after exposure to a cold virus, people develop

• sneezing

• sore throats

• runny noses

• coughing

• chest congestion

• fever

• headaches

• muscle aches

• Colds spread when a person touches a contaminated object or inhales droplets from a sneeze or a cough.

• The flu, or influenza, is a common viral infection of the upper respiratory system.

Influenza

• Influenza is spread by airborne droplets and contact with contaminated objects.

• High fever, sore throat, headache, and a cough are typical symptoms of the flu.

The Stages of the Flu

• In people who are elderly, or who have heart disease or breathing problems, flu may develop into pneumonia (noo MOHN yuh), a serious infection of the lungs.

Pneumonia

• Many people die each year from pneumonia, which can be caused by viruses, bacteria, or even fungi.

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• A group of viruses that infect the liver can cause hepatitis (hep uh TY tis), or inflammation of the liver.

Hepatitis

• Symptoms of hepatitis include • fever• nausea• pain in the abdomen• jaundice (JAWN dis), or yellowing of the skin.

• Hepatitis A is transmitted in human wastes and in contaminated water and food.

• Hepatitis B can be transmitted in blood, during sexual contact, or during tattooing or body piercing.

• Hepatitis C can be transmitted in blood, during sexual contact, or during tattooing or body piercing.

• In most cases, there is no particular medicine that can cure a viral infection.

Treating Viral Diseases

• The best treatments for viral infections are rest, a well-balanced diet, and plenty of fluids.

• Many over-the-counter medicines can treat the symptoms of viral infections.

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• If you are worried about your health for any reason, see a doctor and discuss your concerns with him or her.

When to Seek Medical Care

• Seek professional medical care if you have• an extremely sore throat, earache, vomiting, diarrhea,

or a temperature of 101°F that lasts more than two days

• mucus from your nose or throat that is thick and yellowish green

• difficulty breathing, or severe pain anywhere• a cut, scrape, or sore that does not seem to be

healing as it should• an illness that lasts longer than usual

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Here are some healthful behaviors you should practice to help you avoid disease.

Preventing Infectious Diseases

• Wash your hands several times a day, especially before eating and after using the bathroom.

• Do not share items that can transfer pathogens, such as towels, eating utensils, cups, or hairbrushes.

• Cook and store foods properly. Meats should be cooked thoroughly. Hot foods should be kept hot, and cold foods should be kept cold.

• Avoid close contact with people who are ill.

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Here are some healthful behaviors you should practice to help you avoid disease.

Preventing Infectious Diseases

• Stay home when you are not feeling well.

• Learn to manage stress in healthful ways, and get at least eight hours of sleep each night.

• Eat well-balanced meals, and do not skip meals. Exercise regularly, at least three or more times a week.

• Avoid unhealthful substances, such as tobacco, alcohol, and illegal drugs.

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Using Medicines Correctly

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Read all the information on the label and follow the directions.

Using Medicines Correctly

Only take medicines prescribed for you.

Call your doctor if a medicine causes serious side effects.

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Never combine medicines without checking with your doctor.

Using Medicines Correctly

Never drink alcohol while taking medicines.

Store medicines according to the label’s instructions. (expiration, original container)