AQA GCSE science on pages 18 & 19
Infectious Diseases
A Hungarian doctor called Ignaz Semmelweis was the first to realise that washing hands helps to prevent the spread of disease. He noticed that a number of deaths in one hospital maternity ward was higher than in another. At this time nobody knew about germs, but when he investigated he found that on the ward with more deaths the doctors went straight from dissecting bodies to delivering babies. He asked doctors to wash their hands between tasks and the number of deaths reduced significantly.
Pathogens
Any micro organism that can cause an infectious disease is called a pathogen. Some bacteria are pathogens.
All viruses are pathogens.
All viruses are pathogens.
Bacteria
Not all bacteria are pathogens. We have millions of them on our skin and in our gut and we could not live without them. However, if they get through our gut wall or skin and into our blood or cells they can make us very ill. They reproduce rapidly inside our warm bodies and some produce toxins (poisons) that make us feel ill. Some bacterial toxins may cause death.
Viruses
It is debatable whether viruses are living or not. They are not made of cells, they cannot carry out any life processes. They have to insert themselves into a host cell and hijack that cells parts to make copies of the virus. These new virus particles can then burst out of a cell and infect many other host cells in a 'chain reaction'. Viruses damage and destroy our cells when they infect us in order to reproduce. Viruses are much smaller than bacteria.
Learning Objective
Microorganisms, Pathogen, Bacteria, Virus, Toxin. |
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