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Unit 5 Lesson 5.2 Notes Introductory Video – Infectious Disease Chapter 13: Preventing Infectious Disease Section 1: What are Infectious Diseases? Vocabulary: Infectious disease: any disease that is caused by an agent that has invaded the body pathogen: any agent that causes disease bacteria: tiny, single-celled organisms, some of which can cause disease virus: a tiny disease-causing particle that consists of genetic material and a protein coat fungus: an organism that absorbs and uses nutrients of living or dead organisms antibiotic resistance: a condition in which bacteria can no longer be killed by a particular antibiotic What Causes Infectious Diseases? Infectious disease - Any disease that is caused by an agent that has invaded the body May be passed form a person to another person, from food or water, from animals, or from something in the environment Ex: colds, the flu, head lice, tuberculosis (TB) Caused by pathogens – any agent that causes disease Bacteria Bacteria – tiny, single-celled organisms, some of which can cause disease o Too small to be seen without a microscope o Live everywhere on Earth (even frozen Arctic and boiling waters of hot springs) You have more than 300 kinds of bacteria living in your mouth, but most are harmless and many are helpful! o Ex: bacteria living in intestines make vitamins that you need to live Some bacteria make you sick when they grow inside the body o Give off poisons o Damage cells o Ex: tuberculosis, tetanus, sinus infections Viruses Viruses – tiny disease-causing particles made up of genetic material and a protein coat o Smaller than bacteria Genetic material in the virus contains the instructions for making more viruses o Survive and replicate only inside living cells o Reproduce by taking control of body cells and forcing them to make new viruses o Viruses escape from cells and seek out other cells to attack Ex: colds, flu, measles, AIDS, severe acute respiratory disease (SARS) Fungi Fungi – organisms that absorb and use the nutrients of living or dead organisms Some fungi cause disease o Ex: athlete’s foot – a fungus that lives and feeds on your feet o Ex: ringworm – a fungus that leaves a scaly, circular rash Protozoans Protozoans – single-celled, microscopic organisms o Larger and more complex than bacteria Account for diseases that are leading causes of death throughout some parts of the world o Ex: malaria (kills approx.. 1 mill people each year in tropical countries) Parasites Animal parasites – get their energy and nutrients by feeding on other living things Animal parasites cause a large number of diseases throughout the world o Most infectious disease in the US is from bacteria, viruses, fungi, protozoans Ex: head lice, tapeworms, roundworms How Are Infectious Diseases Spread? Virus is present before you show symptoms Infectious diseases spread in 4 main ways Person to Person When you sneeze / cough you send thousands of tiny drops of saliva and mucus into the air o Drops can remain in the air for a while and carry many pathogens with them o Anyone who breathes in one of these infected drops can become sick from the pathogens o Anyone who touches anything the drops fall on (e.g. a book) can become infected by the pathogens Ex: flu, colds, measles Also spread by kissing, drinking from the same glass, sexual contact o Ex: mononucleosis (aka “kissing disease”) spread through person-to-person contact; can also be spread through sharing food, drinking from same cup Food and Water Foodborne diseases are often spread when pathogens from an infected person or animal contaminate food o This is why people who work with food must wash hands Foodborne disease can also be spread when food is contaminated o Ex: meat from infected animals may also contain eggs of parasitic worms o Ex: hepatitis A and botulism In the US, tap water is safe, but you need to purify lake and stream water o Water can become contaminated if it’s exposed to sewage or animal wastes that have not been treated. o Purify water by boiling it, using water purification tablets, or a filtration system o Diseases include: typhoid, cholera, giardiasis, dysentery Environment Pathogens are present on most of the objects around you Many pathogens cannot live outside the human body, but some are tough and can survive on objects in the environment o Ex: on your phone, on money, in soil and can enter your body through a cut (e.g. tetanus) Animals Many pathogens live in or on animals’ bodies and can carry diseases from one person to another o Ex: ringworm can be contracted by petting a dog or cat that has the fungus Mosquitoes carry a pathogen that causes malaria, yellow fever, encephalitis Ticks carry Lyme disease, Rocky Mountain spotted fever (bacterial diseases) How Are Infectious Diseases Treated? Each pathogen is treated in its own way Treating Bacterial Diseases Antibiotics – medicines used to kill or slow the growth of bacteria o Before antibiotics, even a small cut could lead to a deadly bacterial infection o Prevent the growth and division of bacterial cells, causing them to die o E.g. penicillin, tetracycline, streptomycin o Can’t be used to treat viruses (not for colds or other viral diseases) Antibiotic resistance – a condition in which bacteria can no longer be killed by a particular antibiotic (caused by improper use of an antibiotic) o Today, people are dying from infections that would have been easy to treat 10-15 years ago o Prevent antibiotic resistance by not taking antibiotics if you have a viral disease and using follow the prescription and use all your medication when prescribed an antibacterial Treating Viral Diseases There is less known about how to destroy viruses than bacteria Viruses do not grow as living cells, so viral infections can’t be treated with the same medications as bacterial infections Most antiviral medications concentrate on relieving symptoms an stopping production of viruses inside the human cells o Must be taken early in illness to have an effect Treating Fungal Infections Usually not as common as bacterial or viral infections, but sometimes serious Usually treated with OTC (over the counter) medicine (e.g. athlete’s foot) Others require stronger prescriptions (e.g. candidiasis – yeast infection) Treating Protozoan Infections Prevention is best protection Maintain good hygiene and sanitation If you have a protozoan infection, see a doctor to receive treatment with prescription medicines Treating Parasitic Infections Prevent infection of head lice by not sharing combs or wearing others’ clothes; usually treated with medicated shampoos Section 2: Protecting Yourself from Infectious Diseases Vocabulary: inflammation: a reaction to injury or infection that is characterized by pain, redness, and swelling lymphatic system: a network of vessels that carry a clear fluid called lymph through the body white blood cell: a blood cell whose primary job is to defend the body against disease vaccine: a substance usually prepared from killed or weakened pathogens or from genetic material and that is introduced into body to produce immunity symptom: a change that a person notices in his/her body or mind and that is caused by a disease of disorder How Your Body Fights Disease body fights disease in many ways o uses skin and chemicals to fight pathogens o has specialized defenses, like inflammatory response and immune system body is able to protect itself from pathogens Physical Barriers infection is not easy: o pathogens must enter body, start growing, cause damage body’s first line of defense helps stop pathogens from entering the body skin – uses chemicals (e.g. sweat, oil that kill pathogens on skin) o repairs and rebuilds itself quickly (e.g. closing cuts that pathogens could get through) mucous membranes – soft tissues that line the nose, mouth, throat, digestive tract, urethra, vagina are all mucous membranes o form a barrier to pathogens o make a slimy material called mucus, which traps pathogens e.g. bacteria that you breathe in may get caught in the mucus lining the tubes that carry air to the lungs; cilia (tiny, hairlike structures, grow from the lining of these tubes) move mucus and bacteria to the back of the throat where it’s swallowed and destroyed in the stomach chemicals – chemicals made by your body destroy pathogens o e.g. sweat is acidic and inhibits the growth of bacteria o e.g. stomach secretes acids that not only help you digest food but also kill bacteria o e.g. tears contain a protein that kills bacteria Inflammatory Response sometimes pathogens are able to cross the protective barriers that are your skin and mucous membranes o e.g. when you cut or burn yourself o inflammation – reaction to injury or infection that is characterized by pain, redness, swelling; it’s how your body protects itself from pathogens protective barriers are broken and part of body becomes infected, area around injury becomes inflamed and gets hot o caused by small blood vessels that expand to bring more blood to the injured area o sometimes pus (a yellowish substance) builds up around the injury pus includes dead and injured body cells that were fighting the bacteria and dead and injured bacteria o inflammatory response shows that your body is attacking pathogens Immune System immune system is made up of certain types of blood cells and certain proteins called antibodies o blood cells and antibodies move through the blood vessels and are within your organs lymphatic system - a network of vessels that carry a clear fluid called lymph throughout the body o infection-fighting cells move through the lymphatic system o lymphatic system picks up fluid from all over the body and sweeps up bacteria or viruses and carries them to your lymph nodes (feel in neck just between your ears and jaw) lymph nodes are filled with white blood cells that scan the lymph for pathogens white blood cells – cells in the blood whose primary job is to defend the body against disease white blood cells produce antibodies that bind to specific pathogens and warn other white blood cells to destroy the pathogens when you’re sick, lymph nodes swell b/c of the growing number of white blood cells fighting the infection immune systems defenses take time to defeat pathogens cells of immune system typically attack a specific pathogen body’s other defenses (skin, mucus membranes, inflammation) react to and fight any pathogen What You Can Do to Stay Well protect yourself – keep your body healthy eat a healthy, balanced diet – lack of nutrients can weaken immune system drink water – 8-10 glasses per day to keep immune system working reduce stress – occasional stress is okay, but stress lasting weeks or months can weaken immune system and leave you vulnerable to illnesses and colds exercise regularly – at least 60 minutes per day get regular medical checkups – prevent you from getting sick avoid close contact with sick people – wash your hands, don’t share personal items sleep – keeps body functioning Get Vaccinated vaccines – substances that are usually prepared from killed or weakened pathogens or from genetic material that is introduced into a body to produce immunity o when a vaccine is injected, the immune system responds to the vaccine material by making white blood cells called memory cells. o In the future, if the pathogen for the vaccine enters the body, the memory cells and their antibodies fight the pathogen before it can cause disease Boosters may be needed – extra doses of a vaccine that help the body maintain the production of memory cells for a certain disease You can also be immunized for diseases that develop new strains, like the flu o But you need to get a vaccination each year when there’s a new strain What to Do When Your Are Sick Symptoms of Infection Symptoms – the changes that you notice in your body or mind that are caused by a disease or disorder o E.g. fever, rash, sore throat, headache, muscle aches, fatigue, tired eyes, nausea, omitting, diarrhea Some symptoms are caused by the pathogens o E.g. salmonella bacteria in raw eggs or undercooked chicken and meats cause diarrhea when they invade cells lining the intestine Some symptoms are part of your body’s response to infection o E.g. fever (an increase in temperature) is sometimes caused by the invading microorganisms, but sometimes is a defense against pathogens E.g. some bacteria can’t survive at higher temperatures, so your body temperature rises in an attempt to stunt their growth Taking Care of Yourself Stay home when you feel sick Drink plenty of fluids Follow doctor’s directions Throw away tissues, wash your hands How to Prevent the Spread of Disease Get Vaccinated Vaccination programs have been largely responsible for preventing the spread of infectious diseases Vaccines are important for fighting viral diseases because few drugs can stop a virus once it has begun to reproduce inside the body Keep Clean Maintaining good hygiene is one of the best ways you can prevent spread of disease (washes away bacteria) Count to 10 while rubbing your hands with soap and then rinse well Don't Share Personal Items Don’t share toothbrushes Don’t’ share food or drink Cover Your Mouth! When you sneeze or cough Throw away tissues Be On Guard Outdoors Wear long sleeved shirts and pants in long grass Use bug repellant Avoid animals that are acting strangely Avoid drinking / swimming in remote streams, rivers, lake waters Section 3: Common Infectious Diseases Vocabulary: Meningitis: the inflammation of the membranes covering the brain and spinal cord Salmonellosis: a bacterial infection of the digestive system, usually spread by eating contaminated food hepatitis: an inflammation of the liver amebic dysentery: an inflammation of the intestine cause by ameba Disease Affect Everybody Common Bacterial Diseases bacteria are everywhere many bacteria prefer to lie in dark, warm, moist places (like our bodies) and they grow quickly there strep throat, sinus infection, food poisoning (from undercooked chicken) – all caused by bacteria o meningitis – an inflammation of the membranes covering the brain and spinal cord; can also be caused by viruses or fungi or parasites o salmonellosis – bacterial infection of the digestive system, usually spread by eating contaminated foods Common Viral Diseases Colds and flu are often viral and can be handled by your body Others (e.g. hepatitis) are more serious Other Common Infections Fungal Infections Fungi are important source of food and drugs, but some can be harmful o E.g. athletes foot, jock itch, ringworm Occur most often when type of fungus contacts skin that is warm and moist Skin can become itchy and red and lesions may appear Prevent infection by keeping clothing dry o Maintain good hygiene OTC medicines to kill the fungus Protozoan Infections Most often found in water and soil 20,000 kinds of protozoa exist, but only a small number cause disease o E.g. amebic dysentery, malaria, African sleeping sickness o Amebic dysentery – an inflammation of the intestine caused by an ameba (symptoms: nausea, diarrhea, fever) Malaria – most serious and widespread protozoan infection – o several million people are infected each year o about 1 million people die each year from it o Caused by a protozoan that is passed from one person to another by mosquitoes o Symptoms: fever, chills, headache, fatigue, nausea o Prevented and treated with antimalarial drugs Parasitic Infections Hookworms, flukes, pinworms, tapeworms can live in the body and cause disease Lice, leeches, ticks, fleas can live on the body Spread by o eating infected food, o drinking infected water, o contact with infected soil, o bitten by infected insects body lice are most common parasitic infection in the US o can be seen with the naked eye o cause itchiness and sores on the head o use OTC medications, wash linens, soak brushes in hot water and soap, vacuum carpet and furniture Working Toward a Healthy Future international travel makes it easier to spread disease everyone in the world must work together to fight disease Centers for Disease Control and Prevention (CDC) and National Institutes of Health (NIH)are watching for diseases that my enter the country o Important to have public health system to prevent or manage an infectious disease outbreak o Some countries can afford / don’t have resources for this, so public health is a problem in certain areas of the world o Work to control / eliminate diseases (e.g. measles, mumps, rubella, polio) o Small pox has been eradicated in nature Web Resources Infections National Foundation for Infectious Disease InternetMedicine.com