B5 Communicable Diseases

• communicable diseases can be spread from person to person, e.g. measles. they are spread by pathogens; bacteria or viruses.
• health is a complete state of physical and mental well-being. ill health can be caused by communicable diseases
• tuberculosis is a communicable lung disease and can be fatal. in most people, the immune system can fight this off, however some people have a defective immune system e.g. HIV patients. so they are much more likely to suffer from infectious diseases
• HPV (human papilloma virus) is extremely common. in most people it is harmless, however in some people it can cause cervical cancer
• diseases can be triggered by the immune system e.g. allergies, asthma. in this case, the body is infected with a pathogen that the immune system fights off, but the person is then left with an allergy
• sometimes a mental illness can be triggered by a physical illness. e.g. feeling isolated and depressed from having a disease
• pathogens are microorganisms that cause infectious disease. bacteria, viruses, protists and fungi are all pathogens.
• bacteria can cause food poisoning
• when bacteria enters the body, they reproduce very rapidly, they then release harmful chemicals called toxins. toxins damage tissues and make us feel ill.
• viruses cannot reproduce by themselves. they can only reproduce inside a host cell. the virus will invade the host cell, then reproduce inside the host cell. this will damage the cell, when the virus leaves the cell it can burst open and die.
• pathogens can be spread through the air e.g. water droplets (coughs, sneeze), directly in water (e.g. cholera) and through direct contact between individuals (e.g. HIV)
• HIV can be spread through sexual contact or through sharing needles
• to reduce the spread of pathogens we can wash our hands before eating, provide people with clean drinking water, reduce direct contact e.g. condoms, isolating people with highly infectious diseases like ebola and use vaccinations.
• viruses cannot be killed by antibiotics
• measles is a highly infectious disease that has symptoms like a fever, then patients will develop a red skin rash. usually it is spread through inhaling droplets of someone else
• in some cases of measles, complications can develop causing damage to the breathing system and the brain, as well as being fatal. this is why children are vaccinated against measles when young
• HIV has flu-like symptoms, the virus attacks the cells of the patient's immune system until it becomes severely damaged. at some point it will become so badly damaged that it cannot fight off other infections that most people could, as well as not being able to fight off cancer cells. at this point, the patient is described as having late-stage HIV or AIDS, usually now the disease is fatal
• HIV can be treated using antiretroviral drugs to stop the virus from multiplying inside the patent so the virus doesn't damage the patient's immune system. patients who take these don't go on to develop AIDS and can live with a normal life expectancy
• antiretroviral drugs aren't a cure for HIV or AIDS, the patient must take these for the rest of their life.
• HIV is transmitted through the exchange of fluids between humans, so can be spread through unprotected sexual intercourse and when people share needles because blood containing HIV will pass from one person to the other
• unlike viruses, bacteria can be killed using antibiotics.
• the bacteria that cause salmonella food poisoning are spread by ingesting infected food e.g. the kind of food that is prepared in unhygienic conditions. the salmonella bacteria secrete harmful chemicals called toxins that cause the symptoms of salmonella
• fever, abdominal cramps, vomiting and diarrhea are all symptoms of salmonella
• salmonella bacteria are found in poultry like chickens, however in the UK all chickens are vaccinated against salmonella, preventing the spread of disease.
• gonorrhoea is a sexually transmitted disease (STD). symptoms include a thick yellow or green discharge from the penis or vagina and pain when urinating
• gonorrhoea was easily treated using the antibiotic penicillin, but antibiotic resistant strains are now common. we can stop the spread of gonorrhea using a condom, being tested and treated by antibiotics.
• malaria is a communicable disease spread by a pathogen. the malaria pathogen is an example of a protist.
• people with malaria experience repeated bouts of fever and it can sometimes be fatal
• malaria is spread by mosquitoes. an infected person is bitten, the pathogen will pass into the mosquito. the mosquito will bite a different person and the pathogen passes into them. this mosquito is a vector because it passes a pathogen between people
• to stop malaria, we need to stop the vector (the mosquito) from breeding. mosquitoes breed in still water, so we need to find areas of still water and drain them or spray areas of still water with insecticide to kill them.
• to stop malaria, we can also prevent them from biting humans. this could be done by sleeping under a mosquito net, they can't get through the net so cannot bite anyone sleeping in the bed
• the body has a non-specific defense system and a specific one.
• the job of the non-specific defense system is to prevent pathogens from entering the human body
• the skin is the biggest defense to pathogens. it forms a protective layer covering the body. the outer layer of the skin consists of dead cells and is difficult for pathogens to penetrate. the skin also produces an oily substance called sebum which can kill bacteria
• if the skin becomes damaged, that could allow pathogens to enter, to stop this the skin will scab. platelets will form a clot to create this scab.
• the nose contains micro hairs and mucus, both of which catch pathogens, stopping them from entering the body. if pathogens get through, the trachea and bronchi are covered with tiny hairs called cilia that are covered in mucus to trap pathogens. the cilia will waft the mucus up towards the throat where it is swallowed into the stomach.
• pathogens can be present on food. to protect us, the stomach contains hydrochloric acid, this kills pathogens before they can make their way further down into the digestive system
• the immune system destroys pathogens and any toxins they produce, it also protects us in case the same type of pathogen enters the body again
• white blood cells can ingest and destroy pathogens. the WBC detects chemicals released from the pathogen and moves towards it. it engulfs the pathogen and uses enzymes to destroy it. this process is called phagocytosis
• antibodies are protein molecules produced by white blood cells. antibodies bind to the antigens of the pathogen, triggering the pathogen to be destroyed. they are extremely specific. they remain in the body for a long time, if we get infected again, the body can quickly defend us.