Infectious Disease Definitions Pathogen: Organism that causes disease. Infectious disease: is a disease that can pass from one organism to another. Four Kinds of Pathogens 1. Bacteria: are unicellular microorganisms. MRSA Infection ~ Methicillin Resistant Staphylococcus Aurous Kinds of Pathogens continued 2. Viruses: reproduce inside living cells 3. Fungi: Athlete’s foot 4. Protists: Malaria (1-3 Million Die/Year) African Sleeping Sickness and Malaria Athletes Foot caused by a Fungus! Each Pathogen is Unique! Every species of pathogen has its own unique antigen (large protein that provokes an immune response). For example, every single virus that causes influenza A, has a antigen that is the same. How Diseases are Spread Person to person transfer Contaminated Objects. Animal Bites. The Three Lines of Defense Against Pathogens! Immunity: is the body’s ability to destroy pathogens before they can cause disease. There are two types of immunity: Active and Passive Immunity. Active Immunity Occurs when a person’s own immune system produces antibodies in response to the presence of a pathogen. Example: Flu Vaccination (Substance is called a vaccine) A vaccine is a dead or weak pathogen that stimulates an immune response. Active Immunity usually lasts for many years, and sometimes it lasts for life. Passive Immunity Passive immunity occurs when antibodies come form another source rather than from the person’s own body. Example: Antibodies pass from the mothers bloodstream to the fetus which temporarily protects the fetus. Passive immunity usually lasts no more than a few months. The Body’s Defenses st 1 Line of Defense Barriers such as the sin, breathing passages, mouth, and stomach trap and kill pathogens. Skin – pathogens must get through a thick layer of dead cells packed closely together. Breathing Passages – the respiratory system has mucus and cilia that trap and remove most pathogens. Mouth and Stomach – Saliva contains materials that are destructive to pathogens and the stomach contains acid which is deadly to pathogens. Second Line of Defense The Inflammatory response When a person is cut, certain cells release a chemical called histamine, which causes blood vessels to dilate. In the Inflammatory response, certain types of white blood cells leave the blood vessels and move into nearby tissues. The white blood cells then fight the pathogens. Phagocytosis. You also notice a red area around the cut because of increased blood flow to the area. Inflammatory Response rd 3 Line of Defense If a pathogen infection is severe enough to cause a fever, it triggers a immune response. Your immune response is mainly conducted by WBC’s called lymphocytes. There are two types of lymphocytes. They are B cells and T cells. Third Line of Defense ( The Immune System) B Cells produce antibodies that are used to fight pathogens. Vaccine T Cells T cells directly attack host cells that contain multiplying bacteria or viruses. Aids, A disease of the Immune System Acquired Immunodeficiency Syndrome, or AIDS is a disease caused by a virus that attacks the immune system. How HIV Affects the Body HIV is the only kind of virus known to attack the immune system directly. Once it invades the Body, HIV enters T cells and reproduces inside them. NOTE ( People can be infected with HIV for years before they become sick. How HIV Is Spread HIV can spread from one person to another only if body fluids from an infected person comes in contact with those of an uninfected person. Sexual contact is one way in which this can happen. HIV may also pass from an infected woman to her baby during pregnancy or childbirth or through breast milk. When drug users share needles, some infected blood may get into the needle and then infect the next person who uses it. A person can also get HIV through a blood transfusion of blood that contains the virus.. Ways HIV is not spread It does not live on skin. You can’t get infected by using a toilet seat after it has been used by someone with HIV. HIV is not spread when you bump into someone while playing sports. Summary How Does HIV affect the body? Answer- It attacks the immune system directly. HIV enters the T cells and reproduces. How is HIV spread? 1. From one person to another only if body fluids from an infected person comes in contact with those of an uninfected person. 2. Sexual contact. 3. From and infected woman to her baby during pregnancy. 4. From drug users sharing needles. 5. Through a blood transfusion.