Communicable Diseases

• Health means being free from communicable and non-communicable diseases.

Communicable Diseases

• Communicable diseases can spread from one organism to another and are infectious.
• They can be caused by viruses, bacteria, or fungi.
• AIDS is caused by HIV and spreads through the exchange of body fluids, infected blood, or needles. Prevention includes using condoms and not sharing needles; there is no cure.
• Cold/Flu is caused by a virus and spreads through droplet infection and is prevented with flu vaccinations for targeted groups.
• Mumps, measles, and rubella are caused by a virus and spread through droplet infection; it is prevented by the MMR vaccination.
• HPV (human papilloma virus) is caused by a virus and spreads through sexual contact; it is prevented by the HPV vaccination given to 12–13-year-old girls.
• Salmonella is caused by bacteria and spreads through contaminated food and is prevented by always properly cooking food. Do not mix cooked and uncooked food, and treat with antibiotics.
• Chlamydia (STI) is caused by bacteria and spreads through sexual contact; prevention methods include using a condom and being treated with antibiotics.
• Tuberculosis is caused by bacteria and spreads through airborne droplet infection; BCG vaccination is used; it is treated with antibiotics.
• Athlete's foot is caused by fungus and spreads through contact; avoid direct contact in areas where spores are, and use flip-flops in changing rooms/swimming pools.
• Potato blight is caused by fungus and spreads through spores from plant to plant, especially in humid conditions; it requires crop rotation and spraying plants with fungicide.

Body's Defense Mechanisms

• Skin acts as a barrier to prevent microbes from entering the body.
• Mucous membranes in the nose and respiratory system trap microbes in mucus, which is then expelled.
• Blood clotting closes wounds quickly to prevent microbes from entering and to prevent blood loss.

Role of White Blood Cells

• Lymphocytes and phagocytes are white blood cells that offer protection.
• Lymphocytes detect antigens on invading microbes and respond by making antibodies with a complementary shape.
• Antibodies attach to antigens, causing microbes to clump together and become immobilized, which prevents them from spreading.
• Clumping allows phagocytes to engulf microbes–phagocytosis.
• Memory lymphocytes, produced after an infection, can quickly respond and produce antibodies if the body is infected again by the same microorganism.
• Phagocytes surround and engulf clumps of microbes, then digest and destroy them.

Immunity

• Active and passive immunity are the types.

Active Immunity

• The body produces antibodies to fight infectious microorganisms.
• Slower-acting, as it takes time for lymphocytes to recognize the antigen and respond.
• It usually lasts for a long time.
• Can be acquired by catching the disease or getting a vaccination.

Passive Immunity

• Antibodies from another source are injected into the body.
• It is fast-acting because the antibodies are present in the injection, but it only lasts for a short period of time.
• Allows rapid medical treatment of very serious infections like tetanus.

Aseptic Techniques

• Sterilize petri dishes, culture media (agar or nutrient broth), inoculating loops, and culture bottles by autoclaving, flaming, and alcohol.
• Pass the inoculating loop through a Bunsen flame and allow it to cool.
• Remove the lid of the culture bottle, glide the loop over the surface of the agar (inoculation).
• Replace the lid and sweep the neck of the bottle through the Bunsen flame.
• Spread microbes on the agar in the petri dish by gliding the loop across: plating.
• Keep petri dishes partially covered during inoculation to reduce unwanted microbes entering.
• Work near a Bunsen flame to create an upward current of air, which will carry microorganisms away.
• Flame the metal loop again to kill/destroy all microbes present.
• Incubate sealed petri dishes at a maximum of 25°C to avoid pathogen growth, and preventing microorganisms escaping.
• Clean work surfaces and hands before and after.
• Safely dispose of bacterial cultures by autoclaving.

Active Immunity Graph

• Response follows infection with bacteria or virus.
• A primary response means an individual is often sick for a few days before antibody levels are high enough.
• Antibody level rises slowly but remains high for a long time due to memory of the antigen.
• Secondary response from re-infection causes memory lymphocytes to rapidly produce antibodies to stop the catching illness again.

Passive Immunity Graph

• It involves ready-made antibodies, not produced by the patient.
• It is fast-acting with an immediate antibody level increase, but short lasting, since the body did not produce the antibodies.
• Important for those who catch a disease that could make them very ill before they have a chance to build up their own antibodies.

Vaccinations

• A vaccination contains modified disease-causing microbes to cause antibody production and memory lymphocytes.
• Vaccination mimics having had the disease, but without sickness.
• Memory lymphocytes rapidly produce antibodies to prevent disease development if the body becomes infected later.
• Booster vaccinations are sometimes needed to produce enough antibodies.
• Vaccinations are slow to act but are long lasting.

Antibiotics

• Chemicals produced by fungi used only against bacterial infections and work by killing or preventing bacteria growth.
• Antibiotics cannot treat viral infections because viruses live inside body cells, so they are difficult to kill.
• Often investigations are carried out to determine the correct antibiotic for a particular infection.
• The bacterium is added to a dish, and antibiotics are placed on discs.
• The most effective antibiotic has the largest clear area.

Antibiotic Resistance

• Bacterial resistance to antibiotics is becoming a major problem.
• Bacteria mutate and become resistant due to overuse.
• Resistant bacteria reproduce and pass on the resistant gene to their offspring.
• MRSA is an example of a 'superbug' resistant to most antibiotics.

Eradicating Superbugs

• Antibiotics have no effect.
• Hospitals are an 'antibiotic-rich' environment.
• There are open wounds and weak immune systems.

Reduce Superbugs

• Increase hygiene levels via hand sanitizers.
• Control antibiotic use to not treat viral infections.
• Isolate patients with superbug infections.

Non-communicable diseases

• Non-communicable diseases are not infectious.
• Caused by genes, lifestyle, or both.

Lifestyle Factors and Effect

• Diet with sugar and fat leads to obesity.
• Lack of exercise leads to obesity.
• Overexposure to sun can cause skin cancer.
• Misuse of drugs and alcohol may cause liver damage.
• Smoking damages health.
• Tar causes bronchitis and Emphysema.
• Tar may lead to lung cancer.
• Nicotine is addictive and affects heart rate.
• Carbon monoxide reduces oxygen carried by red blood cells through combination.

Interactions Between Diseases

• Obesity is a risk factor for type 2 diabetes, some cancers, cardiovascular disease (CVD), and hypertension (high blood pressure).
• Obesity can cause cardiovascular diseases and cholesterol buildup.

Heart Attacks

• Cholesterol builds up on the inside wall, causing coronary arteries to narrow.
• This causes restricted blood flow and less oxygen and glucose.
• This leads to less cell respiration and energy reduction in the heart.
• The heart muscle cannot contract.

Strokes

• A stroke occurs after a blockage in the brain.
• Less oxygen and glucose reaches the brain.

Factors Increasing Risk of Heart Attack and Stroke

• Excess fats
• Smoking
• Stress
• Lack of exercise

Angioplasty

• A balloon-like structure that widening arteries.
• A stent keeps them opened to allow increased blood flow.

Statins and Aspirin

• Statins reduce cholesterol.
• Aspirin thins the blood.

Cancer

• Uncontrolled cell division.
• Benign tumors do not spread.
• Malignant these do spread. Lifestyle choices can affect the risk.
• UV radiation causes skin cancer, which can be prevented by use of high factor sun screen and avoiding the hottest sun.
• Tar causes lung cancer, which can be prevented by avoiding smoking and passive smoking.
• HPV causes cervical cancer, which can be prevented by vaccinations.