Causes and Spread of Infection

Fungi are: Fungi are living organisms that are distantly related to plants, and more closely related to animals, but rather different from either of those groups. Fungi have similar physical characteristics to plants and are sometimes mistakenly put in the plant characteristics.

Parasites are: Parasites are living organisms that live and feed on an organism’s or host’s body. They jump from one host to the other damaging the body as they go along the most common carriers like mosquitoes and tick which are never harmed by these parasites.

They may be transmitted from animals to humans, from humans to humans, or from humans to animals. Several parasites have emerged as significant causes of foodborne and waterborne disease. These organisms live and reproduce within the tissues and organs of infected human and animal hosts, and are often excreted in faeces.

1.2 Name some common illness caused by bacteria:

  • Salmonellosis,
  • tuberculosis,
  • MRSA,
  • food poisoning, dysentery,
  • bronchitis,
  • ear infections,
  • strep throat/tonsillitis,
  • gonorrhoea,
  • syphilis,
  • chlamydia


  • Influenza,
  • common cold,
  • stomach flu,
  • pneumonia,
  • ear infections,
  • herpes,
  • warts, dengue,
  • West Nile Virus


  • Valley fever,
  • athlete’s foot,
  • ringworm,
  • yeast infection


  • Worms,
  • malaria,
  • sleeping sickness,

1.3 Infection means: It is the invasion and multiplication of microorganisms in the body tissues, especially that causing local cellular injury due to competitive metabolism, toxins, intracellular replication, or antigen-antibody response.

Colonisation means: it is the presence of bacteria on a body surface (e.g. skin, mouth, intestines or airway) without causing disease in the person. It is also the presence and multiplication of microorganisms without tissue invasion or damage. The colonies develop when a bacterial cell begins

1.4 Systematic infection means: it is an infection in which the pathogen is distributed throughout the body rather than concentrated in one area. Example acute infection, airborne infection, arrested infection, chronic infection, cross infection, etc.

Localised infection means: it is an infection that is limited to a specific part of the body and has local symptoms. it is an infection involving bacteria that invades the body at a specific point and remain there, multiplying, until eliminated.

1.5 Poor practises that might lead to the spread of infection are:

  • not washing your hands,
  • not wearing PPE,
  • not storing or cooking foods properly,
  • not cleaning your surroundings,
  • not covering your nose or mouth when sneezing or coughing.

2.1 The conditions needed for the growth of micro-organisms are (explain a little about each):

  • FOOD Microorganisms need nutrients to grow on and are especially happy with proteins and carbohydrates. These are where the potentially hazardous foods come in, such as meats, poultry, dairy and eggs.
  • ACIDITY. the measurement of how acidic or alkaline something is. The range starts at 0.0 and goes to 14.0 with 0-6.9 being Acidic, and 7.1-14 being alkaline. Microorganisms tend to find themselves most happy in the slightly acidic range of 7.5-4.6, which also happens to be where most foods lie.
  • TEMPERATURE. micro-organisms grow best between 40°-141°F. Going outside the danger zone may not kill them, but merely slow their growth rates.
  • TIME. Microorganisms need time to grow and given the right environmental conditions, they are capable of doubling their numbers in just 20 minutes. If you leave food in the danger zone for e.g. 4 hours or more, the levels of Microorganisms can be high enough to make someone ill.
  • OXYGEN. micro-organisms need oxygen to grown, but not all of them necessarily do. Botulism is one of the tough organisms that are anaerobic, which means it does not require any oxygen to multiply.
  • MOISTURE. Most foodborne microorganisms need some amount of moisture to grow, but again not all. The moisture in potentially hazardous foods is just right to provide the organisms what they need to grow.

2.2 An infection agent might enter the body by:

  • Down the respiratory tract into the lungs
  • Breaks in the skin.
  • Down the digestive tract.
  • Up the urinary and reproductive systems.

2.3 Common sources of infections are:

  • Airborne
  • Blood borne
  • sexually transmitted
  • faecal oral transmission
  • cross contamination

2.4 Infective agents can be transmitted to a person by:

  • intradermal – through the piercing of skin and letting germs enter
  • through respiratory tract – by inhaling it
  • absorbing some things through the skin, such as chemicals.
  • obtain diseases through having sex with infected person
  • one can be injected deep into muscle, through infected needles or other sharp objects
  • one can be infected through contaminated IVs
  • it can be through eating (ingesting) something that has infectious germs
  • one can get urinary tract infections by wiping the wrong way with soiled toilet tissue.
  • you can get vaginal infections by wiping the wrong way with soiled toilet tissue

2.5 Key factors that will make it more likely that infection will occur are:

  • dirty and/or contaminated areas,
  • equipment
  • contact with body fluids
  • very young children (babies)
  • elderly people.

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