1.3 Describe what is meant by infection and colonisation

This guide will help you answer 1.3 Describe what is meant by infection and colonisation.

Health and social care workers meet a wide range of situations involving infections. Understanding infection and colonisation is important for anyone working in this sector. These terms help us understand how diseases start, develop and spread among people.

What is Infection?

Infection is when harmful micro-organisms, such as bacteria, viruses, fungi, or parasites, enter a person’s body and begin to multiply. These micro-organisms are sometimes called pathogens, which means “germ” or “disease-causing bug.” If the body’s defences do not stop these invaders, they may multiply, causing damage to body tissues. This can result in symptoms and signs of illness.

Some frequent examples of infections include:

• Chest infections, which may be caused by bacteria or viruses
• Urinary tract infections, often caused by bacteria
• Wound infections, where bacteria get into a cut or surgical wound
• Gastroenteritis, commonly caused by viruses or bacteria

The process of infection has several stages:

1. Entry. The pathogen finds a way into the body, such as through the mouth, nose, skin, or a wound.
2. Multiplication. The pathogen starts to grow in number.
3. Spread. The pathogens move within the body, sometimes spreading from the original site to other areas.
4. Damage. The pathogens may cause inflammation or destroy body cells, leading to illness.

How Infection Occurs

For an infection to develop, certain conditions need to be met. The “chain of infection” helps people understand how germs spread and cause illness:

1. Infectious agent: The microbe that causes the infection.
2. Reservoir: Where the pathogen lives and grows (e.g., people, animals, dirty surfaces).
3. Portal of exit: How the pathogen leaves its reservoir (coughing, sneezing, bleeding).
4. Mode of transmission: How the pathogen moves to a new host (hands, air, food, water, contact).
5. Portal of entry: How the pathogen enters the new host (mouth, nose, skin, wounds, eyes).
6. Susceptible host: Someone who can become infected (a person with low immunity, elderly people, or those already unwell).

Breaking this chain at any point helps stop the spread of infection. Proper hand hygiene, cleaning, use of protective clothing and safe handling of waste all help to interrupt this process.

Signs and Symptoms of Infection

When the body detects invading pathogens, it puts up its defences. The immune system acts to try to destroy the germs. This response causes the typical symptoms of infection:

• Fever or raised temperature
• Redness and swelling (inflammation)
• Pain
• Pus or discharge from wounds
• Tiredness
• Loss of appetite
• Feeling generally unwell

Infections can be mild, like a common cold, or severe, like pneumonia or sepsis, which is a life-threatening reaction to infection.

What is Colonisation?

Colonisation means that micro-organisms are present and living on or in the body but are not causing sickness or symptoms. Our bodies naturally carry many bacteria—known as the “normal flora”—on the skin, in the gut and sometimes in other areas. These normal micro-organisms do not usually cause disease and can be helpful.

Colonisation, in a care context, usually refers to people carrying potentially harmful bacteria, such as MRSA (Methicillin Resistant Staphylococcus aureus), without showing any signs or symptoms. The bacteria may be found, for example, in the nose, throat or on the skin.

Key points about colonisation:

• Micro-organisms are present on the body or within body systems.
• There are no signs or symptoms of illness.
• The person does not feel unwell because of these micro-organisms.
• Colonised people can still transmit germs to others.

Differences Between Infection and Colonisation

It is important to understand the difference between infection and colonisation, as the terms are often confused in health and social care settings.

Infection	Colonisation
Pathogen multiplies and damages body tissues	Pathogen is present but not causing harm
Body develops symptoms	No symptoms
Needs treatment in most cases	May not need treatment
May be short-term or long-term	Can persist for a long time with no harm
Can spread to others	Also can spread to others

For example, someone may carry MRSA on their skin and appear healthy (colonised). Another person may develop a wound infection with MRSA and become seriously unwell (infected).

Types of Micro-organisms

To understand infection and colonisation, you need to know about the different types of micro-organisms:

• Bacteria: Single-celled organisms. Most are harmless, some help us (such as in digestion), and some cause disease.
• Viruses: Much smaller than bacteria. They infect our cells and use them to reproduce. Examples include flu and COVID-19.
• Fungi: Includes yeasts and moulds. Some cause minor infections like athlete’s foot.
• Parasites: Live on or in another organism, causing harm. Examples: head lice, scabies, and worms.

Example Scenarios

To make the difference clear, consider these workplace examples:

Colonisation Example:
Janet works in a nursing home. She is tested for MRSA during a routine screening. The swabs from her nose come back positive for MRSA, but she feels well, has no wounds, cough or fever. Janet is colonised with MRSA. She is not ill and may never become ill from this. However, if she needs surgery or develops a wound, the MRSA could cause an infection.

Infection Example:
Robert lives in the same nursing home. He has a pressure sore on his heel that begins to swell and ooze pus. He develops a temperature and feels shivery. The wound swab grows MRSA. Robert is showing clear signs of infection—his body is reacting to the MRSA, which is harming his tissues.

The Importance for Health and Social Care Workers

Correctly recognising the difference between infection and colonisation helps workers make safe decisions. Here’s why it matters:

• Staff know when to take extra precautions, like isolation and use of gloves or aprons.
• It helps in planning care. Some colonised people need cleaning or screening but not antibiotics, while infected people may need treatment.
• It stops unnecessary use of antibiotics, which helps lower the risk of antibiotic resistance.
• It supports good communication with colleagues and visiting healthcare professionals.

Risks and Precautions

People who are colonised can still spread germs—even if they are healthy. This is why regular hand hygiene and cleansing surfaces is important. Infections can be more dangerous for people who are older, have weak immune systems, are pregnant or already have illnesses.

Key preventive steps include:

• Washing your hands after contact with each person.
• Wearing gloves and aprons where appropriate.
• Keeping the environment clean and removing waste safely.
• Paying attention to wounds, catheters, feeding tubes or any break in the skin.

Communication with Individuals

Care workers should explain the difference to the person and their family. For colonisation, inform them that:

• Carrying the germ usually does not cause harm.
• There is usually no reason to have antibiotic treatment.
• Good hygiene helps prevent spread.

For infection, explain:

• Symptoms may need medical review or treatment.
• There may be extra precautions to protect others.
• Treatment (sometimes antibiotics) may be needed.

This helps reduce worry and confusion.

How Health and Social Care Settings Respond

Organisations have guidelines to manage infection and colonisation:

• Early identification—screening for “high risk” bacteria when people come into care homes or hospitals.
• Risk assessment—deciding if extra steps are needed.
• Monitoring for symptoms.
• Isolating infected people if needed.
• Training staff to recognise symptoms and respond properly.

Documenting and reporting are important so that outbreaks are managed quickly.

Common Misunderstandings

• People sometimes think carrying a germ means they will always become sick. This is not true; colonisation may never cause harm.
• Not everyone with a cough or sore is infected—sometimes symptoms are due to other causes.
• “Superbugs” like MRSA can be present on the body without causing any issues.

Your Role as a Health and Social Care Worker

Be aware of the difference between infection and colonisation:

• Know who is at risk in your workplace.
• Watch for early signs of infection, especially with wounds, tubes or fevers.
• Follow hygiene and cleaning routines every time you provide care.
• Keep up to date with your training and organisational procedures.
• Communicate clearly with other staff and with those you support.

How Infection and Colonisation Relate to Good Practice

Effective infection prevention supports the wellbeing and health of those receiving care. It lowers the risk of outbreaks, keeps staff and individuals safe and builds public trust in care services.

Consistent hand washing, wearing personal protective equipment, cleaning rooms, safe disposal of waste, and checking for early signs of infection are all good practice.

Final Thoughts

Infection means harmful micro-organisms enter the body, multiply, and cause illness or symptoms. This needs watching, reporting and often treatment.

Colonisation means micro-organisms live in or on a person, usually with no symptoms or illness. Colonised people may still carry and spread germs, but do not need the same treatment as those with infection.

Being clear about these terms helps you provide better care, reduce risks, and support the health and dignity of those you assist. Understanding these differences is a foundation of safe and effective health and social care practice.