Chain of infection

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:

  1. infectious agent or the microorganism which can cause disease

  2. 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

  3. 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 gastroenteritis microorganisms would be transmitted in the faeces or vomit

  4. 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

  5. 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.

  6. 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 of infection.

Select image for full size version.

Chain of infection diagram alt text This diagram shows the 6 different links of the chain of infection. A diagram showing 6 links of a chain interlinked is in the middle of the diagram with the 6 boxes around it. Here is the description of the 6 boxes. Infectious agent: This is the microorganism or bug that can cause harmful infections and make you ill. Common infections in care homes are respiratory such as cold and flu and stomach bugs like norovirus and clostridiodes difficile (C.diff) Reservoir: This is where the germ lives and grows. This can be on a person for example in their respiratory tract or equipment, environment or on food and water., Portal of exit. Way out: The germ then needs to find a way out of the infected person and then to spread. Ways out can be from sickness and diarrhoea and through the nose and mouth from coughing and sneezing. Mode of transmission: Once the germ is out it can spread from one person to another by hands or on equipment such as a commode, in the air by coughing or contact with blood and body fluids. Portal of entry. Way in: The germ then needs to find its way into another person. This can be through the eyes or mouth, hands, open wounds or any tubes that go into the body such as a catheter or feeding tube. Susceptible host: This is the person who is at risk of infection as they are unable to fight the infection. This could be residents, staff or visitors. Elderly people can have a decreased immune system and catch infections easier. Infections also spread quickly in care homes due to many residents living together.

Use the NES SIPCEP Breaking the Chain of Infection module to learn about breaking the chain of infection in care homes. 

 

 

Reducing risk

The hierarchy of controls (HoC) is a system used to help prevent the transmission of infection. It details the most to least effective controls.  You will note that PPE is the last level of control in the hierarchy, used when all other controls have not reduced the risks sufficiently. To be effective, PPE must be used correctly which means putting it on and removing it correctly and safely.

See the Health and Safety Executive’s (HSE) toolkit on management of risk when planning work: the right priorities for additional information.

 

The HoC principles can be broadly interpreted for care home settings and include:

Examples of HoC principles

Here are some examples of how to apply the HoC principles in care home settings. These examples do not cover every situation where you might need to use HoC principles.

Reducing hazards in the care home

Measures such as vaccination, testing and isolation help to reduce the risk of infection. Not coming to work when ill, isolating while infectious and recognising and reporting infections promptly, all help to prevent infections spreading.

Changing practice in the care home

When faced with a particular risk, such as an outbreak, we may need to change what we do. This might include reducing communal activities, considering limiting visiting for a short period of time, or cleaning the care home environment more frequently. The local IPCT and/or HPT should always be contacted for advice and support in outbreak situations.

Making the care home as safe as possible

It is very unlikely that we will be able to change where we work but the care home setting should be made as safe as possible. You can reduce opportunities for pathogens to survive in the care home, ensuring fixtures and fittings are in good repair and can be easily cleaned and following water safety guidelines. Ventilation is also an effective measure to reduce the risk of some respiratory infections, by diluting and dispersing the pathogens which cause them. Consider opening windows and vents more than usual, even opening a small amount can be beneficial. Opening windows and doors may present security and safety issues and so a local risk assessment should always be undertaken.

Changing how we organise and work in the care home

Changing the way, we organise and work in the care home can also help reduce risk. This might include reducing the number of people in a space at any one time and minimising the movement of staff between different settings as well as using administrative controls. Administrative controls include local risk assessments, staff training, IPC audits, and providing clear signage and instructions throughout the care home.