Bacteria - can cause TB, anthrax, legionaires.
Virus - can cause HIV, flu, cold.
Fungus - can cause athletes foot, thrush.
Microorgamisms reproduce faster in warm and damp places.
Symptoms can be caused by damage to the cells directly by microogranisms (like HIV taking over white blood cells).
Symptoms can also be caused by toxins created by the microorganisms - ecoli cause diarrhoea by releasing toxic chemicals.
Your body has defence against microogranisms - examples include: skin, sweat, bile in stomach, tears in eye, hydrocloric acid in stomach.
The lymphocytes make antibodies that attach to the antigens.
The phagocytes engulf the pathogens - this is called phagocytosis.
The first time you encounter a microorganism, you get ill- your body hasn't encountered this before and it doesn't have the antibodies needed. The time you get ill is the time it takes for your body to make the antibodies to fight it off - this time, there is a plataeu in the level of how many antibodies your body has.
Once you get better, the level of antibodies for this microorganism doesn't lower completly - some antibodies stay behind as memory cells so that when your body encounters it again, there is a quicker response because it can easily make more antibodies.
When you are vaccinated, you are injected with a weakend or dead form of the pathogen - this is so that your lympocytes can recognise it, create antibodies, and keep some memory cells so that when you encounter the pathogen for real, you can quickly fight it off.
Some people don't want to get vaccinated - they don't think that they will get the disease or they might be worried about the side effects.
Vaccines are only effective if the majority of the population gets them - it 95% of the population are vaccinated, they can offer a herd immunity to people who don't get the vaccination - this is where enough people have got it to make it very unlikely for the people without the vaccnation to become infected.
When microogranisms reproduce, the DNA sometimes mutates - this changes the structure and characteristics of the microorganism.
Some viruses, like the flu and cold have a high mutation rate - you need a new vaccination each year for the flu and cold because by the time the next year comes, the virus has mutated.
HIV has a very high mutation…