Germs are microscopic organisms that enter your body and cause harm.
The scientific word for germ is ‘pathogen.
When germs begin to multiply inside your body, you are suffering from an infectious disease.
An infection that spreads throughout your body (flu or measles, for example) is called a systemic infection.
An infection that affects only a small area (such as dirt in a cut) is called a localized infection.
It is often the reaction of your body’s immune system to the germ that makes you feel ill.
Bacteria are single-celled organisms. They are found almost everywhere in huge numbers, and multiply rapidly.
Most bacteria are harmless, but there are three harmful groups – cocci are round cells, spiral bacteria are coil-shaped, and bacilli are rod-shaped. These harmful I bacteria cause diseases such as tetanus and typhoid.
Viruses can only live and multiply by taking over other cells – they cannot survive on their own. They cause diseases such as colds, flu, mumps and AIDS.
Parasites are animals such as tapeworms that may live in or on your body, feeding on it and making you ill.
Fungal spores and tiny organisms called protozoa can also cause illness.