Causes and Spread of Infection

Unit 265
Causes and spread of infection
Outcome 1
Identify the difference between bacteria, viruses, fungi and parasites

Bacteria are organisms made up of one cell, but have the capability to divide, and can therefore multiply by themselves. They have a wide range of shapes ranging from spheres to rods and spirals. Bacteria exist everywhere, even inside the human body. Most of them are harmless and some are very useful eg gut bacteria produce vitamins and help people digest food, but some bacteria can cause disease. People have more bacteria cells in their bodies than human cells.
Bacteria can cause food poisoning, which is why it is necessary to ensure food is cooked thoroughly and store certain foods in the fridge. Bacterial infections can be cured with antibiotics, but using them too often can stop antibiotics working as they build up a resistance. MRSA is a resistant form of bacteria found on the skin, which can cause infections after surgery.
Viruses are simpler than bacteria and are made up of genetic codes of DNA or RNA, long molecules that carry genetic information and a protein shell. They cannot reproduce on their own and need to take over another cell, animal, plant or human. Some viruses eg bacteriophages, are useful and can kill the bacteria that is harmful in food.
Most diseases are caused by a virus, like flu or a cold. Other diseases are chickenpox, measles, mumps, German measles and HIV which causes AIDS. If a person has a virus eg chickenpox, it usually makes them immune to having it again. Vaccination can also help build an immunity to prevent most viral infections. Viruses cannot be cured with antibiotics, but there are a few antiviral drugs which have been developed. They can be passed on by sneezing, coughing, or from coming into contact with someone who has a virus.
Fungi are any of a group of unicellular, multicellular, or syncytial spore-producing organisms which unlike bacteria can grow in low...