HOW ARE INFECTIONS SPREAD?

1. HOW ARE INFECTIONS SPREAD? The Chain of Infection

2. Micro-organisms • There are many types of micro-organisms. Not all cause illness, some live in or on some part of the body (skin, mouth, intestinal tract) and are called the normal flora. They may cause an illness if they find their way into another part of the body. • Normal skin flora is called ‘resident’ and is there all the time. It rarely causes infection. • Micro-organisms which are deposited or acquired from other staff or residents or the environment, are known as ‘transient’. They do not live permanently on the skin are readily removed or destroyed by thorough and frequent hand hygiene.

3. Reservoirs • Reservoirs of micro-organisms can be people, the environment or equipment. • The human body is the biggest and best reservoir for micro-organisms and most common source of infection. The micro-organisms are present in some of the body fluids and can be passed on to others. • Contaminated food may act as a reservoir. For instance, food not thoroughly cooked can infect individuals who consume it. • The environment can become contaminated by micro-organisms shed by people with an infection and become a reservoir for spread to others. • Poorly maintained or incorrectly maintained equipment can also act as a reservoir of micro-organisms.

4. Point of entry • All micro-organisms need a point of entry, for instance: • The mouth for the salmonella bacteria • The Nose and mouth for the micro-organisms causing tuberculosis, which then make their way to the lungs • The bloodstream until the liver for the hepatitis B virus • A catheter if poorly cared for can lead to urinary tract infections.

5. Point of exit • All micro-organisms need an exit point, for instance: • Salmonella bacteria are excreted through faeces • Tuberculosis bacterium uses the same entry and exit points (lungs, mouth and nose)

6. Method of spread or mode of transmission • All micro-organisms need a mode of transmission. Hands play a big part in spreading infection. The modes of transmission include: • Aerosol • Droplet • Faecal – oral • Direct contact (person to person) • Indirect contact (food, water, fomites, environment) • Blood and body fluid • Insects and parasites

7. Susceptible host • For infection to occur once micro-organisms have reached their ‘target’, the person must be at risk of infection. Infection is caused by organisms that evade the host’s immunological defence mechanisms, although susceptibility to infection may vary from person to person.

8. Risk factors for infection • Factors that affect a person’s susceptibility to infection include: • Age (the very young and very old are more susceptible) • Immune status • Physical well-being • Psychological well-being • Hygiene • Underlying or chronic diseases or medical conditions • Other existing infections • Medical interventions • Medical therapies

9. Principles of asepsis It is the responsibility of all staff to understand and incorporate the following principles into their everyday practice. These key principles have been developed to prevent contamination of wounds and other susceptible body sites: • Keep the exposure of the susceptible site to a minimum • Ensure appropriate hand decontamination prior to procedure • Use sterile or non-sterile gloves depending on nature of site or procedure undertaken • Protect uniform/clothes with disposable plastic apron • Ensure all fluids and materials are sterile • Check sterile packs for evidence of damage or moisture penetration • Ensure contaminated/non-sterile items are not placed in the sterile field • Don’t re-use single use items • Reduce activity in the immediate vicinity of the area in which the procedure is to be performed