B1a4 Infectious Diseases

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Microorganisms that cause infectious diseases are called pathogens.  Examples of some pathogens are shown in the picture below.


Bacteria and viruses can reproduce rapidly inside the body and may produce toxins (poisons) which make us feel ill.  The bacteria which cause food poisoning (e.g. Salmonella and Campylobacter) often produce toxins.  Viruses live inside cells and hijack the cells machinery to make lots of copies of themselves.  They often damage cells when the reproduce and the cell may burst open to release lots of copies of the virus which can then go on to infect new cells.

The human body provides an ideal environment for pathogens to grow and reproduce as it provides a warm environment with a good supply of nutrients.  Under ideal conditions bacteria can reproduce every 20 minutes.

Medicines such as paracetamol and aspirin help to relieve the symptoms of infectious diseases but they do not kill the pathogens.