Disease

• 3 types of microorganism

• Virus - the smallest microogasnism, infects by injecting a host cell with a strand of DNA turning the cell into a factory of viruses. These then break out of the cell and spread through the body.
• Bacteria - these single celled organisms infect by entering the body on food and drink or by being inhaled. The body then rovides ideal living conditions and they multiply rapidly causing the syptoms of the disease
• Fungi - Usually appears as a blemish on the skin examples include diseases such as athletes foot, ringworm and thrush

• the main treatment for viruses is vacination. This works by injecting a weakened form of the disease into the body which is then fought by the immune system. If the real disease appears the body can fight it faster
• bacteria are treated with antibiotics. These kill the harmful bacteria but can also kill the useful bacteria as well. It is important to finish the course as not doing so can cause resistant bacteria to emerge. An example of this is the MRSA disease (methicillin-resistant staphylococcus aureus).

• White blood cells fight diseases in two ways
• They surround and digest the microorganisms
• They produce antibodies and memory cells (antibodies make the microorganisms clump together so that more can be destroyed at once, memory cells remember the disease so that if it reapperars it can be fought faster)

Stomach acid also helps to destroy microorganisms that enter the body on food before they enter the blood stream