Many human infections are caused by either bacteria or viruses. Bacteria are tiny single-celled organisms, thought by some researchers to be related to plants. They are among the most successful life forms on the planet, and range in habitat from ice slopes to deserts.
Bacteria can be beneficial – for instance, gut bacteria help us to digest food – but some are responsible for a range of infections. These disease-causing varieties are called pathogenic bacteria. Many bacterial infections can be treated successfully with appropriate antibiotics, although antibiotic-resistant strains are beginning to emerge. Immunisation is available to prevent many important bacterial diseases.
A virus is an even smaller micro-organism that can only reproduce inside a host’s living cell. It is very difficult to kill a virus. That’s why some of the most serious communicable diseases known to medical science are viral in origin.
How bacteria and viruses enter the body
To cause disease, pathogenic bacteria must gain access into the body. The range of access routes for bacteria includes:⇔ Cuts
⇔ Contaminated food or water
⇔ Close contact with an infected person
⇔ Contact with the faeces of an infected person
⇔ Breathing in the exhaled droplets when an infected person coughs or sneezes