WJEC Biology for A2: Student Bk

Side effects Most medical drugs have side effects and many cite this as a reason not to vaccinate their children. Considering the complexity of living systems, it would be extraordinary if a molecule affected one aspect only of the body’s biochemistry. Common side effects include soreness at the injection site, fever, fatigue and muscle or joint pain. Serious side effects have been documented, but because of the rigorous testing required for vaccines, these are extremely rare. The attention they get in the mass media makes them seem more common that they really are. An example relates to the triple vaccine for measles, mumps and rubella, MMR. The percentage of children receiving the MMR vaccine fell from 92% to under 80% following a 1998 publication, in which a link between the vaccine and the onset of autism was suggested. A case study Measles is a highly contagious air-borne viral infection accompanied by a whole body rash and fever, sometimes in excess of 40 º C. Complications occur in about 30% of cases and include diarrhoea, blindness, brain inflammation, pneumonia and even death. A vaccine was introduced in 1963. In the UK, about 97% of the population was vaccinated and since then, from being a common childhood disease, measles became extremely rare. However, in 1998, misleading claims about the MMR (measles, mumps and rubella) combined vaccine, suggesting a link between the vaccine and the onset of autism, were published. They led to the percentage of the population vaccinated dropping. The claim was discredited but great damage was done. In Wales, the uptake of the MMR vaccine fell from 94% of two-year-olds in 1995 to 78% by 2003. In the Swansea area, uptake fell to 67.5%. Between November 2012 and July 2013, there were 1,455 measles notifications in the whole of Wales and 664 of them were in Swansea; 88 people were hospitalised for measles and a 25-year-old man died from complications. The cost associated with treating the sick and controlling that outbreak alone approached £500,000. Going further Emerging diseases Emerging diseases are infectious diseases in humans that have increased in frequency over the last 20 years or are likely to do so in the near future. Many such infections are correlated with increased global interconnectedness and close interactions between humans and animals. They include: • A new disease caused by an unknown microbe, e.g. HIV-AIDS • A disease found in new areas, e.g. West Nile virus in the Western hemisphere, causing encephalitis. • A microbe developing resistance to antimicrobial agents, e.g. meticillin-resistant Staphylococcus aureus (MRSA). • A microbe from an animal that now infects humans, e.g. avian ‘flu. • Evolution producing a change in a microbe, e.g. most E. coli strains are relatively benign, but O157:H7 can cause severe illness. • An organism that has been deliberately altered to cause intentional harm, e.g. Bacillus anthracis , which causes anthrax, was used to contaminate mail in the USA in 2001. A recently emerged disease is Ebola hemorrhagic fever (EHF). It is a viral disease causing fever, sore throat, muscular pain and headaches, then, vomiting, diarrhoea and a rash, with decreased liver and kidney function. Some people bleed both internally and externally. It is fatal in 25–90% of cases, often because of low blood pressure from fluid loss. It was identified in tropical sub-Saharan Africa in 1976 in two simultaneous outbreaks and now occurs intermittently. The largest outbreak was the west African epidemic, from December 2013 to January 2016. Option A: Immunology and disease 277