Causes and Spread of infection

Understand the causes of infection

1:1 Identify the differences between bacteria, viruses, fungi and parasites

The differences between bacteria, viruses, fungi and parasites are;

  • Fungi have cell walls made up of chitin (found in outer skeleton of insects, shrimps and lobsters – also used in healing agents). Fungi and parasites are multi cellular (Ref:
  • Viruses are not living, they are only made of complex proteins and nuclear acids
  • Bacteria are unicellular micro-organisms
  • Parasites and bacteria are animals

(Bacteria, fungi and parasites are living organisms) (Dundas & Welsby 2002, pp99-106)

1:2 Identify common illnesses and infections caused by bacteria, viruses, fungi and parasites

Common illnesses and infections caused by bacteria, viruses, fungi and parasites are;


  • Chicken pox
  • Shingles
  • Laryngitis
  • Pneumonia
  • Mumps
  • Common cold
  • Aids
  • Whooping cough
  • Measles


  • Malaria
  • Intestinal
  • Scabies
  • Ringworm
  • Tapeworm
  • Crab louse


  • Conjunctivitis
  • Athletes foot
  • Ringworm
  • Thrush
  • Fungal nail
  • Intertrigo (yeast)


  • Colds
  • Flu
  • Fevers
  • Meningitis
  • Pneumonia
  • Gastroenteritis
  • Impetigo
  • MRSA
  • Severe gastrointestinal (caused by E-coli)
  • Acne

(Brooker &Nicol 2003, pp254-255)

1:3 Describe what is meant by “infection” and “colonisation”

The meaning of colonisation occurs when micro-organisms inhabit on a part of the body for example, skin but don’t cause signs and symptoms of infection colonised pathogens have the potential to cause infection if spread to a different parts of the body depending on the micro-organism colonised pathogens which can be passed on from person to person from touching objects or not washing hands. This is a major route of colonisation within the health care facilities. Colonisation of micro-organisms can inhabit the host by being in or being on, they don’t cause damage or invade the tissue, yet if they do invade tissue this can make the person sick, which in turn will turn into an infection.

Even though the host may not show signs of illness, they can still pass it on to others. (Lister & Dougherty 2008, pp1112-1113)

1:4 Describe what is meant by “systemic infection” and “localised infection”

The skins function is to protect the body from infectious organisms, but when there has been a break in the skin infections can pose a threat. The meaning of localised infection is an infection that is limited to a specific body region. The meaning of systemic infection is when the pathogen is distributed throughout the whole body by the bloodstream.

Systemic infection:

  • Conjunctiva infection can cause lasting damage if not treated in time
  • Low immune systems due to diabetes, kidney failure etc.
  • The elderly or children may cause complications with infection due to their age

Localised infection:

  • Swelling
  • Redness
  • Temperature changes in infected area

1:5 Identify poor practices that may lead to the spread of infection

Covered on ECA course Training centre

Understand the transmission of infection

2:1 explain the conditions needed for the growth of micro-organisms

The conditions needed for the growth of micro-organisms are nutrients for them to reproduce. It also requires warmth and moisture. They are not visible with the naked eye. The factor that encourages the growth of micro-organisms is nutrition, oxygen, temperature, PH and moisture. The PH and temperature determines the rate of growth. The moisture carry’s foods into the cell, and carry’s the waste away from the cell to maintain the content of cytoplasm (ground substance in where different components are found). All micro-organisms have a PH at which they can grow. (Brooker & Nicol 2003, pp.254-255)

2:2 explain the ways an infective agent might enter the body

An infective agent might enter the body through the mouth, stomach, intestines. The digestive tract. It can also be through broken skin.

Areas of infection:

The respiratory system – nose, lungs, windpipe.

The digestive system – spoiled food, unclean hands or objects.

The urinary tract – urethra, bladder, kidneys.

Wounds on the skin – cuts, grazes, trauma to the skin.

There is also secondary infective agent:

Genital – sexually transmitted, non-sexual PH imbalance (soaps, sprays, creams).

Conjunctival – to the eye (dust, viruses, bacteria, contact lenses)

The ways that gains entry to the person is by infecting the cells:

Trauma bite – infected animal, human, insect

Congenital – unborn baby (developed through pregnancy. Rubella, chickenpox, herpes, syphilis)

2:3 Identify common sources of infection

The best source for infection is poorly chilled, heated or contaminated food. Contaminated laundry on a low heat setting, clinical waste, and contaminated equipment, others that may be infected. Unclean work surfaces in kitchens. We all come into contact with hands, some just don’t take hand hygiene seriously and will spread the infection further afield.

2:4 Explain how infective agents can be transmitted to a person

Airborne – inhalation of pathogens (microorganism disease producing agent such as bacteria, virus). The common cold and flu spread the infection to another person, either sneezing into the air, nasal droplets; this may be from a nebuliser. Infected dust particles containing skin scales may cause a respiratory virus.

Direct contact – this would be person to person contact, such as dirty hands upon a patient or other way around. Sexual intercourse, chicken pox/shingles (herpes zoster) with the rash and until the last blister has dried up. Impetigo (staphylococcus aureus) which mainly affects children and immune suppressed people.

Hands – are the main part of cross-infection. This can be transferred by microbes to other body areas, for example: hand to face to phone (communal), to shared computers, to person with a handshake. They in turn have now picked up everything you have touched. If they don’t wash their hands, the cycle of cross infection will multiply too many others. With the ambulance cross contamination can be spread from person to equipment including steering wheels, radios, door handles. Your body’s blueprint may have a good resistance to bacteria in your genes, but others you treat or touch may not and could potentially make them very ill.

Indirect contact – can be spread by fomites – an inanimate object that becomes contaminated with infectious organisms and then transports those organisms to another person. This can include children’s toys, chopping boards, baby’s nappies, oxygen masks, Entonox breathing adaptors. They can live for a few minutes or a few hours. Indirect contact can also be spread by crawling or flying insects these are examples of vectors these are organisms that transmits pathogens and parasites (person, insect, animal)Insect bites may cause a variety of infections, one being malaria.

Ingestion – the organisms that infect the gastro-intestinal tract are ingested through the mouth by objects such as the hands, in drink, uncooked food, faecal/oral spread, eating food with unclean hands. Cross infecting would be to eat food while sharing communal keyboards/laptops who would in turn pass on to others by contracting sickness and diarrhoea and by not following hand washing techniques, this will continue until the cycle is broken.

Inoculations – there may be a chance of a “needle stick” injury caused by infected needles that may contain Hepatitis B virus, and as the inoculation has been put directly into the blood stream of the patient, an infection is high.

2:5 identify the key factors that will make it more likely that infection will occur

The key factors that will make it more likely that infection will occur are individuals susceptible to infection; these would include older people with lowered immunity due to other illnesses or conditions, children or babies. Compromised circulation secondly to peripheral vascular disease. People with diabetes have a risk of developing infections if their blood sugar is lower than normal. Urinary catheters or percutaneous endoscopic gastrostomy tubes (PEGS). IV lines if kept in too long (when a paramedic inserts a needle to administer drugs, you should note the time and date it was inserted and place on the surrounding site of the needle, this keeps hospital staff aware the length of time it has been in). Poor personal hygiene can be a factor and open to infections. Areas around skin folds due to obesity, as infections build up in moist areas such as the groin, stomach and under the breasts, infections can multiply rapidly in these areas. Young and premature babies with under developed lungs and heart, this is due to the lungs not being fully developed affecting the oxygen levels in the cells. Infection may be more if the patient or person is contact with contagious agents.

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