What is one method of controlling the agent in breaking the chain of transmission

In our last blog post, we looked at the crucial role cleaners play in breaking the chain of infection in hospitals. But infection prevention and control (IPC) isn’t just down to the cleaners. It is the responsibility of everyone working in the hospital, including doctors and nurses, and of course, the dedicated IPC team.

Here, we summarise the four key factors that are crucial for breaking the chain of infection in hospitals.

1. Isolation and cohort nursing

Isolation of infected patients is an important component in preventing the spread of infection in hospitals. The purpose is to contain the organism and its mode of transmission, rather than the patient.

The Health and Social Care Act 2008 requires that all hospitals provide adequate isolation precautions and facilities, have policies in place for how to allocate patients to isolation facilities, and ensure that they can keep infected patients separate from others.

Individual patients with an infection should be isolated in single rooms or side rooms. When there are not enough single rooms to isolate individual patients, cohort nursing should be undertaken. This is where patients with the same organism, e.g. MRSA, or those displaying similar signs and symptoms, can be nursed together. The cohort may consist of an entire bay of infected patients, in which case the patients should be cared for by designated staff in a dedicated area of the ward.

Isolation and cohort nursing break the chain of infection by containing the organism in specially appointed areas so that it can’t spread to other patients, staff, equipment or surfaces within the hospital.

2. Hand hygiene

Alcohol gel dispensers and signs to wash your hands can be seen all over hospitals – and for good reason. Hand hygiene is the single most important intervention that hospital workers can undertake to prevent the spread of infection. It has been estimated to reduce the spread of hospital-acquired infections (HAIs) by 15-30%.

Organisms present on the skin of infected patients can shed onto nearby objects or equipment, allowing it to be transferred to the hands of hospital staff, where it can survive at least several minutes. If the staff member washes their hands or uses alcohol gel, they kill the organisms before they can transfer them to the next patient, object or equipment they come into contact with.

There are many reasons hand hygiene may sometimes be overlooked by staff. Not least because there are often so many other tasks that demand a staff member’s attention in such a busy hospital environment. Ensuring there are plenty of alcohol gel dispensers, conveniently located within the hospital, is crucial – as well as making sure they are regularly re-filled. Introducing personal bottles of hand gel can also increase hand hygiene significantly. Our recommendations for hand hygiene can be found here.

3. Personal protective equipment

The importance of personal protective equipment (PPE) has been a highly topical subject of late. The shortage of PPE during the coronavirus outbreak in the UK demonstrated just how crucial it is in preventing the spread of infection.

In line with EPIC and NICE guidelines, the selection of PPE should be based on a risk assessment of the risk of transmission to the patient or staff member, and the risk of contamination with blood, body fluids, secretions and excretions or exposure to chemicals. Aprons, gowns and gloves are the most commonly required PPE, as well as surgical face masks and respiratory protection – such as in the case of caring for patients with coronavirus.

Just as important as having the appropriate PPE is using it correctly. The incorrect use of gloves and disposable plastic aprons increases the risk of cross-infection to patients, equipment and the environment.

Putting on PPE is often the first thing healthcare workers do when preparing for a task or patient care, but actually, it should be the last thing they do. This is so that there’s no risk of accidental contamination before they even make it to the patient. Healthcare workers must also not leave a bay or room wearing PPE – unless there is an emergency or they are removing a bedpan.

PPE intended for single-use should also not be reused. This was where a lot of the criticism around COVID-19 came from, as many healthcare workers complained of having to re-use masks and share them between colleagues. Many studies have been done around the effectiveness of decontaminating reusable PPE, including by University Hospital Southampton using the ProXcide hydrogen peroxide technology. The Inivos strategy for decontaminating reusable PPE, including our recorded webinar on the subject, is here.

4. Environmental decontamination

Environmental decontamination also plays a critical role in breaking the chain of infection. There has been a growing body of evidence in recent years to show that contaminated surfaces are a key contributor to the spread of infection from person to person. This is because pathogens and multidrug resistant organisms can easily be shed from infected patients and survive on dry surfaces for hours, days, or even months at a time.

Manual cleaning is an important first step, but, on its own, is not enough to break the chain of infection. In the case of an outbreak, enhanced cleaning methods such as increasing the frequency of cleaning, using extra staff to target ‘high-touch’ surfaces and bringing in teams for ‘high risk’ areas can be beneficial. Disinfection is also equally important, as cleaning alone isn’t effective enough to inactivate certain microbes such as viruses and spores.

But the most effective methods for environment decontamination involve specialist automated technologies. These systems use either ultraviolet (UV-C) light or hydrogen peroxide vapour (HPV) to eliminate pathogens from the environment.

UV-C kills microorganisms by destroying the nucleic acid and disrupting their DNA. UV-C decontamination is most appropriate if a ward is experiencing an extremely high volume of patients, as it can reduce pathogens within 45 minutes and, in some cases, in as little as 3 minutes. HPV kills microorganisms by a process of oxidisation which destroys the cell wall. HPV decontamination is arguably more effective than UV-C but does take longer – up to two hours.

More hospitals are turning to automated decontamination systems for effective infection prevention and control. Used in addition to manual cleaning and disinfection, they give cleaning staff the reassurance that they are delivering the best possible service for patients, visitors and staff.

All these methods work together to break the chain of infection. Isolating infected patients helps to contain the organism and its mode of transmission. Correct use of PPE prevents pathogens from being transmitted from infected patients to other patients, staff and visitors, as well as equipment and objects within the environment. And good hand hygiene and environmental cleaning kills the pathogens to prevent them from being spread between people and surfaces.

Updated February 2021 with infographic linked above

Healthcare acquired infections (HAIs) are the result of a sequence of events that take place between an infectious agent (or pathogen), a host and an environment – in a process that is referred to as the ‘chain of infection’.

Understanding how infections become established in healthcare settings is crucial for effective infection prevention and control.

In this blog post we explore the six key links in the chain of infection, together with the actions that can be taken to disrupt the chain.

The 6 links in the chain of infection

1. The pathogen

The first link in the chain of infection is the infectious agent or pathogen which can take the form of:

• Viruses – such as Influenza A, shingles and Hepatitis
• Bacteria – including Lyme disease and Leptospirosis
• Fungi – for example Candidiasis and Aspergillosis
• Parasitic protozoan diseases – such as Malaria, Giardia and Toxoplasmosis
• Prions – which are the cause of rare progressive neurodegenrative disorders such as Creutzfeldt-Jakob disease (CJD)

How well any pathogen is able to thrive depends on three factors:

• Its pathogenicity – its ability to produce disease
• Its degree of virulence – its severity or harmfulness
• Its invasiveness – its tendency to spread

2. The reservoir

A reservoir is the principal habitat in which a pathogen lives, flourishes and is able to multiply.

Common reservoirs for infectious agents include humans, animals or insects and the environment.

Human reservoirs

In humans, there are two forms of reservoir: acute clinical cases (in which someone is infected and is displaying signs and symptoms of the disease); and carriers (where someone has been colonised with an infectious agent but is not unwell.

Acute clinical cases are more likely to be diagnosed and treated which means that the patient’s contacts and normal activities will normally be restricted. Carriers, however, can present more of a risk to those around them because they do not display any signs or symptoms of illness.

Carriers can be further subdivided into four main types:

• Incubatory carriers – people who are infectious even before their own symptoms start
• Inapparent carriers – in which an individual is able to transmit an infection to others, without ever developing the infection themselves
• Convalasecent carriers – people who are in the recovery phase of their illness but who continue to be infectious
• Chronic carriers – anyone who has recovered but who continues to be a carrier for infection.

Animal & insect reservoirs

Examples of animal or insect reservoirs include Lyme disease (which is transmitted via ticks); Rabies (which is transmitted by dogs, cats, foxes and bats); and Salmonella (which is transmitted by poultry, cattle, sheep and pigs).

Any infectious disease that is transmitted under natural conditions from animal to human is referred to as zoonosis.

Environmental reservoirs

The environment contains a large number of reservoirs of infection, including soil (which acts as a reservoir for Clostridium tetani, the causative agent of tetanus) and water (which is a reservoir for Legionella pneumophila, the causative agent of Legionnaire’s disease).

3. The portal of exit

The portal of exit is any route which enables a pathogen to leave the reservoir or host. In humans the key portals of exit are:

• Alimentary – via vomiting, diarrhoea or biting
• Genitourinary – via sexual transmission
• Respiratory – through coughing, sneezing and talking
• Skin – via skin lesions
• Trans-placental – where transmission is from mother to foetus

4. The mode of transmission

The two main ways that an infection can be transmitted from its reservoir to a susceptible host are via direct transmission or indirect transmission.

Direct transmission tends to be instantaneous and occurs when there is direct contact with the infectious agent. Examples include tetanus, glandular fever, respiratory diseases and sexually transmitted diseases.

Indirect transmission can occur through animate mechanisms such as fleas, ticks, flies or mosquitoes or via inanimate mechanisms such as food, water, biological products or surgical instruments.

Indirect transmission can also be airborne, in which tiny particles of an infectious agent are carried by dust or droplets in the air and inhaled into the lungs.

5. The portal of entry

The portal of entry is the means by which an infection is able to enter a susceptible host.

Portals of entry into the human body include:

• Inhalation (via the respiratory tract)
• Absorption (via mucous membranes such as the eyes)
• Ingestion (via the gastrointestinal tract)
• Inoculation (as the result of an inoculation injury)
• Introduction (via the insertion of medical devices)

6. The susceptible host

The last link in the chain of infection is the susceptible host.

How susceptible any host will be, depends on a variety of factors:

• Their age – and in particular if they are very young or very old
• Whether there is any presence of malnutrition or dehydration
• Whether there is any underlying chronic disease
• If the host suffers from immobility
• If they are taking any medication which could disrupt or suppress their immune response
• General resistance factors (such as mucous membranes, skin, cough reflex etc) that can help defend against infection

How can we break the chain of infection?

The healthcare environment can expose patients to infection risks that they may not encounter elsewhere.

Understanding how infections become established, and how they are transmitted, is essential for effective infection prevention and control.

There are opportunities to break or disrupt the chain at any link: though the rapid and accurate diagnosis of an infectious disease; the prompt treatment of infected patients; the safe disposal of waste; the sterilisation and disinfection of medical equipment or the implementation of an environmental decontamination strategy.