Immune System

I. The Immune System and Transmission of Infectious Diseases The immune system attacks and destroys invaders that enter the body. Pathogens are organisms or substances that cause disease (germs) Antigens are any non-living substance that is foreign to the body and triggers an immune response (i.e., splinter, plant pollen, viruses)

Diseases can be spread by: Direct contact (shaking hands, sharing body fluids) Indirect contact (sneezing, coughing) Water and Food (eating foods or drinking water infected with pathogens) Animal bites

II. Fighting Infections a) 1st Line of Defense – Body prevents pathogens from infecting host Skin and linings of all internal organs Sweat and oil (slightly acidic, preventing some pathogens from growing) Gastric juice secreted by the lining of the stomach Mucus and Cilia (line the nose preventing pathogens from entering respiratory system)

Describe what each of the following “entry points” do to prevent entry of pathogens into the body: Entry blocked by… Eyes Tears, eyelashes Ears Ear wax Nose Mucus, cilia Mouth (and stomach) Gastric juice

b) 2nd Line of Defense - Body mounts an immune response to an attack Two Types: Innate Immune Response Acquired Immune Response

I) Innate Immune Response - general, non-specific (same for any invader) fluid, cells and dissolved substances in the blood flow to the site of infection this results in fever, swelling, and redness (inflammation) 

white blood cells in the blood engulf intruders, destroying them – called PHAGOCYTOSIS  https://www.youtube.com/watch?v=X-ubCIcAh4M

II) Acquired Immune Response - more specific attack on a particular pathogen Consists of 4 stages: Recognition Mobilization Disposal Immunity

1. Recognition when body is invaded by a foreign substance, the body recognizes it as not belonging The body uses white blood cells to recognize infection and to fight the invading disease-causing agent, or pathogen.

Phagocytes engulf (eat) the invading bacteria and signal Helper T cells to find B cells and tell them to produce antibodies.

2. Mobilization B cells make antibodies, which bind to antigens to make them harmless or mark them for destruction by other white blood cells Must have a perfect fit = lock and key This can take time – this is why you can be sick for days/weeks.

3. Disposal Once the right antibody that fits the antigen is found, they are mass produced and clump onto the invading pathogen, marking it for destruction.

Killer T cells kill the body’s own cells that have been invaded by pathogens, preventing the pathogen from reproducing in the cell and then infecting other cells.

4. Immunity Some antibodies remain for future use – you usually cannot have the same disease twice!

3.2 Factors Affecting the Immune System I. Vaccinations Vaccines are weakened pathogens given to people to protect them from getting a disease. Vaccines stimulate your body to create antibodies to destroy the pathogen. These antibodies will activate when the pathogen enters the body again. Booster shots increase the antibody production and extend the immune system’s memory for that antigen.

II. Disorders of the Immune System ALLERGIES: An allergy is an unusually high sensitivity to a substance. Any substance that causes an allergic reaction is called an allergen. Side effects of an allergic reaction are a result of histamine. Histamine is a chemical that your body releases when you need to fight invaders. Severe allergies can cause anaphylactic shock (swelling, breathing difficulties, and sometimes death).

III. AIDS/HIV Acquired Immunodeficiency Syndrome (AIDS) is an infection of the immune system that leads to health complications and often death. AIDS is cause by the human immunodeficiency virus (HIV) that attacks the immune system by infecting Helper T-cells.

AIDS is transmitted by blood and semen. There’s no cure for HIV/AIDS, but a variety of medications can be used in combination to control the virus.

IV. Taking Care of your Immune System Eat a well-balanced diet Maintain personal hygiene (bathing, washing hands, brushing teeth) Keep home clean Avoid tobacco and other non-prescription drugs Get plenty of rest and exercise Keep vaccinations up to date Do not engage in activities that involve sharing body fluids with others.

Epidemics and Pandemics

A disease is said to be endemic when it is at a constant, “normal” occurrence within a given geographical area. In this case, low numbers of people become sick. A disease becomes an epidemic when it affects an unusual number of people in a community or region at the same time. A higher number of people become sick.

Characteristics or an epidemic: When the # of people infected rises above what is expected. Illness is specific to a certain area. Usually caused by circulation among people.

Examples of Epidemics: seasonal flu outbreaks happen each year Norovirus outbreaks have occurred on cruise ships in 2003, the severe acute respiratory syndrome (SARS) epidemic took the lives of nearly 800 people worldwide in 2014, the Ebola virus resulted in 6070 deaths in West Africa

Pandemics A disease is a pandemic when it becomes prevalent throughout an entire country, continent, or the whole world. Thousands to millions of people become sick.

Characteristics of a pandemic: Causes serious illness.  illness spreads easily from person.  is an outbreak of global proportions.  usually caused by a new form of a virus or bacteria.

Examples of Pandemics: Spanish flu killed 40-50 million people in 1918 The Franco-Prussian War triggered a smallpox pandemic of 1870–1875 that claimed 500,000 lives HIV/AIDS  In 2009, H1N1

How many people die from a pandemic depends upon: The number of people who become infected The severity of disease caused by the virus (its virulence) The vulnerability of affected populations The effectiveness of preventive steps

The World Health Organization (WHO) provides an influenza pandemic alert system, with a scale ranging from Phase 1 (a low risk of a flu pandemic) to Phase 6 (a full-blown pandemic): Phase 1: A virus in animals has caused no known infections in humans. Phase 2: An animal flu virus has caused infection in humans. Phase 3: Sporadic cases or small clusters of disease occur in humans. Human-to-human transmission, if any, is insufficient to cause community-level outbreaks. Phase 4: The risk for a pandemic is greatly increased but not certain. Phase 5: Spread of disease between humans is occurring in more than one country of one WHO region. Phase 6: Community-level outbreaks are in at least one additional country in a different WHO region from phase 5. A global pandemic is under way.

How to prevent the spread of diseases? The best way to prevent a virus from becoming a pandemic is to get a vaccination.  Wash your hands often with soap and water. If these are not available, use an alcohol-based hand cleaner or gel sanitizer. If using a gel, rub your hands until they become dry.

Avoid touching your mouth, nose, or eyes with your hands unless you've just washed your hands. When you cough or sneeze, cover your mouth and nose with a tissue. Then throw the tissue in the trash. Wash your hands afterward.

Avoid crowded places as much as you can and stay home if you show signs of illness. Depending on the severity of the pandemic, consider wearing a face mask if you must go into a crowded area or be within 6 feet of others. Consider wearing a face mask if you must come into close contact with an infected person.