Infection and response

• Communicable diseases are diseases that can be spread from one person to another
• Communicable diseases are spread by pathogens
• Pathogens may be viruses, bacteria, protists and fungi
• Non-communicable diseases cannot be passed from person to person, for example coronary heart disease
• Ill health can be caused by both communicable and non-communicable diseases
• Bacteria produces toxins that damage cells and viruses are replicated inside cells
• Pathogens are microoganisms that cause infectious disease
• When bacteria is inside of a body, it reproduces very rapidly and it can release harmful chemicals called toxins. Toxins can damage tissues and make people ill
• Not all bacteria are pathogens. Some bacteria are beneficial to humans.
• Viruses cannot reproduce by themselves. They can only reproduce inside a host cell
• The virus needs to go inside of the host cell and reproduce inside of it
• Some pathogens can be spread in the air (water droplets)
• Some pathogens can be spread directly in water
• Some pathogens can be spread by direct contact between individuals
• Reducing the spread of pathogens can be washing your hands/having good hygiene, using protection during sexual intercourse and drinking clean water. People can also isolate themselves at home to prevent pathogens spreading
• Measles is a viral infection that causes a red rash and fever
• Measles can be spread by the inhalation of droplets from coughing and sneezing
• Measles can cause blindness and brain damage
• In the UK, there is vaccinations for young children to get so that it prevents them from getting measles
• HIV: human immunodeficiency virus, a retrovirus which causes AIDS
• HIV starts with a flu-like illness but if it is untreated it can travel to the lymph nodes and attack cells of the immune system. It can stay hidden in the immune system for many years until the immune system is very badly damaged it can no longer deal with other infections or cancers. This is known as AIDS, a very late stage of HIV
• HIV can be spread by direct sexual contact and the exchange of bodily fluids
• There is no cure for HIV, however there is a use of antiretroviral drugs used for the early stage and it can control the disease to slow down or halt the progress of AIDS
• Tobacco Mosaic Virus (TMV) is a virus that causes yellowing of leaves and stunted growth
• TMV is only a plant pathogen and it is a fungal disease
• The symptoms of TMV are distinctive mosaic patterns of discolouration of the leaves as the virus infects the chloroplast. The plant will also not grow as much due to the lack of photosynthesis - this reduces the yield of crops
• TMV can be spread by plants in direct contact with an infected plant. The virus can stay in the soil for about 50 years
• There is no treatment for TMV but to prevent it happening is having good field hygiene
• Fungal diseases can affect humans, one example is athletes' foot. This is spread by contact with surfaces that have been touched by an infected person, such as shower room floors
• Fungal infections are more common in plants and can destroy crops or a plant
• Rose black spot is a fungal disease. This is where purple or black dots develop on leaves, which usually turn yellow and drop early. This affects the growth of plants as photosynthesis is reduced
• The spread of rose black spot can be from water or air
• The treatment of rose black spots is to use fungicide chemicals. The leaves can also be removed or burned to prevent the spread of the infection over another plant. Farmers may breed a variety of plants together so that they have a resistance to the disease
• Samonella is a bacteria disease that causes food poisoning and is spread by eating contaminated food
• Symptoms of salmonella are a fever, stomach cramps, and diarrhoea
• Chickens in the UK are vaccinated against Salmonella and having good hygiene in the kitchen to prevent Salmonella happening
• Gonorrhoea is a bacteria disease and it is a sexually transmitted disease (STD)
• The symptoms of gonorrheoa are: thick, yellow or green discharge from the vagina or penis and pain when urinating
• Gonorrhoea is spread by unprotected sexual contact
• The treatment of gonorrhoea are using antibiotics and using protections (contraception) during sex