1. They Make Us Sick
Diseases

2. Bacteria
A disease is anything that causes your body to stop working properly
Bacteria are microscopic, unicellular (one cell) organisms
There are thousands of them
Bacteria are an important part of the natural environment
They are decomposers
Bacteria living in the intestines of herbivores help with digestion

3. Bacterial diseases
Pathogenic bacteria causes hundreds of diseases eg. Whooping cough, meningococcal disease
These are all infectious diseases, they are diseases that can be spread
Some infectious diseases are easier to spread than others
Those that are easiest to spread are described as contagious

4. Quarantine is used to prevent the spread of disease within a community, between communities and between countries
Bacterial infections are treated with antibiotics
The first successful antibiotic was penicillin
Before the development of antibiotics, you had to depend on your body’s immune system to fight off infection

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6. Parasites
Parasites are organisms that lives in or on another organism. The parasite benefits while usually harming the host organism.
Parasites that live inside your body are called endoparasites and those that live outside your body are called ectoparasites

7. Prions They are non-cellular pathogens
They are abnormal and infectious proteins that can convert your normal protein into prion protein.
When cells containing prions burst the infectious proteins are released to infect other cells

8. Viruses
Viruses caused many common illnesses, such as colds and flu, measles, chicken pox and polio
Viruses are smaller than bacteria
Viruses only reproduce in cells they have invaded – host cells

9. A virus uses the host cell to make thousands of copies of itself
The host cell is destroyed when it bursts open and releases new viruses that spread throughout the body, infecting and destroying other cells

10. Fungi
Fungi organisms, such as mushrooms and moulds, that help to decompose dead or decaying matter. Many are parasites, and these can lead to disease.
Many fungi are parasites, feeding on living plants and animals
Common human diseases caused by fungi are tinea , ringworm

11. The Immune System
Pathogens can enter your body a number of ways eg. Food, water, breathing in, cuts, sexual contact
Your body has three lines of defence.
The first line of defence is to stop pathogens entering the body. Eg. the skin, tears and saliva, nose hairs and mucous lining the trachea; and the chemical barriers such as saliva, tears, stomach acid

12. Once the pathogen enters the body tissues, the second line of defence starts: inflammation
White blood cells consume the bacteria, and the dead white blood cells form the yellow pus that collects around the wounds
Third line of defence is the lymphatic system, which contains lymph nodes which has different types of white blood cells , which destroy pathogens

13. Vaccination To help out the immune system vaccines are used
Vaccines are chemicals that cause your body to react as if it met a pathogen

14. A vaccine is created by taking a small amount of poison produced by the bacterium and making it inactive, or by using dead bacteria
The inactive poison and the dead bacteria are harmless, but your immune system responds to the vaccine by making antibodies and you become immune to the pathogen

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