In order for infection to occur several things have to happen. This is often referred to as the Chain of Infection. The six links in the chain are:
- The Infectious Agent – or the microorganism which has the ability to cause disease.
- The Reservoir or source of infection where the microorganism can live and thrive. This may be a person, an animal, any object in the general environment, food or water.
- The Portal of Exit from the reservoir. This describes the way the microorganism leaves the reservoir. For example, in the case of a person with flu, this would include coughing and sneezing. In the case of someone with gastro-enteritis microorganisms would be transmitted in the faeces or vomit.
- The Mode of Transmission. This describes how microorganisms are transmitted from one person or place to another. This could be via someone’s hands, on an object, through the air or bodily fluid contact.
- The Portal of Entry. This is how the infection enters another individual. This could be landing on a mucous membrane, being breathed in, entering via a wound, or a tube such as a catheter.
- The Susceptible Host. This describes the person who is vulnerable to infection.
Infection can be prevented by breaking the Chain of Infection.
The chain of infection diagram illustrates and gives examples of actions that can be taken to break it. The overall aim of Standard Infection Control Precautions (SICPs), is to break the Chain.
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