Back to Microbes


Any micro-organism that causes disease in other living things is called a pathogen.

Viruses cause diseases such as:- influenza, mumps, measles, chickenpox, ebola and the common cold.
Bacteria cause diseases such as:- sore throat, tetanus, tuberculosis, syphilis, leprosy and pneumonia.
Fungi cause diseases such as:- athlete's foot and ringworm.


The human immune system has the job of killing pathogens. The immune system therefore has to be able to tell the difference between the cell of a pathogen and one of its own cells. The way it does this is by recognizing proteins on the cells of pathogens. Once the pathogen has been recognized, your immune system will arrange to have it killed. The problem is, it can take a long time for the human body to recognise the proteins on a pathogen and by then, it might be too late.
To help the immune system fight disease, we can inject a vaccine. A vaccine is a preparation of dead or weakened pathogens or sometimes just sections of the pathogen that contain the important proteins. This is injected into a human so that their immune system can get used to the proteins of a particular pathogen and prepare an immune response so that if the human is ever infected with the disease for real, then the immune system will be able to cope with it much better.

Vaccination video