Unit 22 - Causes and Spread of Infection

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1.1 Identify the differences between bacteria, viruses, fungi and parasites Bacteria are one celled organisms (not all of which are harmful). Some types of bacteria live and multiply in the environment whereas others are adapted to be inside human or animals hosts. Rates of multiplication can vary from minutes to months depending on the type of bacteria. Viruses are much smaller than cells and are basically just a capsule that contains genetic material. They have to invade cells and use the cellular machinery to live and reproduce. They are known to hijack almost every type of organism – including bacteria. Antibiotics have NO effect on viruses. There are many types of fungi – many of which we eat (like mushrooms) or use as ingredients in our food (like yeast). Others exist in the environment as spores of moulds A parasite is an organism that lives on or in another organism, harming the host. 1.2 Identify common illnesses and infections caused by bacteria, viruses, fungi and parasites Bacteria Tuberculosis Urinary tract infections Viruses Influenza Herpes Chickenpox and shingles Fungi Ringworm Candida Parasites Malaria Tapeworms 1.3 Describe what is meant by ‘infection’ and ‘colonisation’ sometimes we can have a disease causing organism living on/in us but not be showing symptoms of illness this is known as colonisation. If the organism is making us ill this is infection. 1.4 Explain what is meant by ‘systemic infection’ and ‘localised infection’ A systemic infection is in the bloodstream and has spread or is spreading around the body. They normally spread through the bloodstream and most of the infectious diseases known to the general public are examples of systemic infections (AIDs, flu, tuberculosis) Localised infections remain in one part of the body and do not cause problems

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