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  • Created by: Amy
  • Created on: 19-02-12 19:37


*       An infectious disease is caused by a microorganism entering and attacking the body. People can pass these microorganisms from one person to another. this is what we mean by infectious, 

Microorganisms that cause diseases are called pathogens. Common pathogens are bacteria and viruses. 

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how pathogens cause disease

How pathogens cause disease:

- bacteria and viruses cause disease because once they are inside the body they reproduce rapidly. bacteria simply split in two. they often produce toxins (poisons) which affect your body. sometimes they directly damage your cells. viruses take over the cells of your body as they reproduce,damaging and destroying them. they very rarely produce toxins. 

common disease symptoms are a high temperature, headaches and rashes. these are caused by the damage and toxins produced by the pathogens. 

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The differences between bacteria and viruses;

- Bacteria and single celled living organisms that is much smaller than plant and animal cells. 

- it is made up of cytoplasm surrounded by a membrane and a cell wall. Inside the bacterial cell is the genetic material. 

-although some bacteria cause diseases, many are harmless and some are really useful to us. We use them to make food like yoghurt and cheese, in sewage treatment and to make medicines. 

- Viruses are even smaller than bacteria. 

- They usually have regular shapes.

- A virus is made up of a protein coat surrounding simple genetic material.

-they do not carry out any of the functions of normal living organisms except reproduction; 

- They can only reproduce by taking over another living cell. And as far as we know all naturally occurring viruses cause diseases, 

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when ignaz semmelweiss was a doctor in the mid- 1850's, many women who gave birth in hospital died a few days later. they died from childbed fever, but noone knew what caused it.

-semmelweiss realised that his medical students were going straghit from dissecting a dead body to delivering babies without washing their hands. he wondered if they were carrying the cause of a disease fromt the corpses to their patients. 

-he insisted that his medical students wash their hands in an antiseptic solution before delivering a babies. immediately, fewer mothers died. the antiseptic solution killed bacteria 

many doctors thought that childbed fever was gods punishment to women, they didnt want to accept the idea that the disease was caused by something invisible passed on from patient to patient. also, it was hard for doctors to admit that they might have spread the disease and killed their patients instead of curing them. 

- it took years for semmelweiss idea to be accepted because handwashing seemed strange in the 19th century. 

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