| Features| Illnesses Caused|
Bacteria| Can be helpful, can be an aid in digestion, able to break down sewage, can be used in food (yoghurt), affects odour, taste and texture. Needs nutrients, pH, time, temperature, +/- Oxygen and water activity to grow.| Lyme disease, Tuberculosis| Viruses| Exist only to replicate, need a host, infect all types of cells, found in soil, water and air.| Hepatitis A, Norovirus, Measles, Mumps| Parasites| Need a host (nourishment, protection, complete life cycle), found in soil, water air and animals, acquired via contaminated food, water and contact with a contaminated source.| Anisakiasis, Giardiasis, Cryptosporidiosis, Trichinosis, Taeniasis| Fungi| Reproduce via spores e.g. yeasts, moulds. | Tinea pedis, Oral thrush| A Pathogen is an agent that produces disease. There are four categories; Bacteria, Viruses, Parasites and Fungi. Here is a table, which shows the differences between them:
An infection, in general terms, is the illness caused by the growth of a germ on or in a person. Sometimes the infection does not give any symptoms – this is called an ‘asymptomatic’ infection. When the germ is commonly found on our body without causing an illness, it is called carriage or colonisation. Carriage may be very short term (transient). For example, acquired by touching someone but quickly removed by washing your hands, or persistent with the germ multiplying on your body (usually called colonisation). In certain circumstances, the germs that colonise our bodies may go on to give an infection. 1.4
Systemic infection is a generic term for an infection caused by microorganisms in animals or plants, where the causal agent (the microbe) has spread actively or passively in the host’s anatomy and is disseminated throughout several organs in different symptoms of the host. Systemic infections are also called disseminated infections, and they can be caused by bacteria and...