Infectious Diseases: How Do You Break the Chain?
Published: 04 April 2023
Published: 04 April 2023
As a healthcare worker, it’s crucial for you to update your knowledge on the spread and containment of infectious diseases, and what you can do to help break the chain of infection and contain the spread.
Infectious diseases are illnesses caused by pathogenic organisms, including viruses, bacteria, fungi and parasites. They may be transmitted by people, animals (zoonotic diseases) or environmental sources (e.g. water), depending on the specific pathogen (Mayo Clinic 2022).
Infectious diseases differ from non-infectious diseases (noncommunicable diseases) such as deficiency diseases, hereditary diseases and cardiovascular diseases, because rather than being related to internal factors such as lifestyle and genetics, they are caused by organisms that are not naturally found in the body (Aakash BYJU'S 2022).
The symptoms and severity of infectious diseases vary greatly depending on the pathogen causing them (Mayo Clinic 2022).
Bacteria are small, singular cells that are able to survive in a variety of environments - sometimes in extreme cold or heat - without a living host. Bacteria exist in the body naturally and are mostly harmless, but can sometimes cause infections. Bacterial infections can usually be treated with antibiotics (Mayo Clinic 2023).
Common bacterial infections include (but are not limited to):
(Healthdirect 2022)
Viruses are tiny microbes, even smaller than bacteria. They comprise a segment of nucleic acid (DNA or RNA) surrounded by protein. Viruses invade and multiply within the cells of a living host and cannot survive on their own (Healthdirect 2022; Mayo Clinic 2023; NHGRI 2023).
Viral infections include (but are not limited to):
(Queensland Health 2015)
Fungi are single-celled or multicellular organisms that reproduce using spores. They include moulds, yeasts and mushrooms (Biology Dictionary 2019).
There are millions of fungi species, most of which are harmless. Only a few hundred varieties can cause illness (CDC 2022a).
Fungal infections include (but are not limited to):
(CDC 2019)
Parasites are organisms that live in or on another organism and feed on them. Their size varies, with some parasites large enough to be visible with the naked eye (Sepsis Alliance 2022).
Disease-causing parasites are separated into three main classes:
(CDC 2022b; Ho 2019)
Parasitic infections include (but are not limited to):
(CDC 2022c)
The series of events enabling infections to spread between organisms is known as the ‘chain of infection’. There are six steps or ‘links’ in the chain that continue to repeat, and breaking any of these links will allow the chain to be dismantled (Reuter 2023).
The pathogen that causes the infection (Reuter 2023).
The habitat where the infectious agent is living and multiplying. This can be a human, animal, object or environmental source such as water or soil (Reuter 2023; NFID 2016).
The means through which the infectious agent escapes from the reservoir. Examples include bodily excretions, open wounds and aerosols (Reuter 2023; NFID 2016).
The way in which the infectious agent spreads from one place to another (Reuter 2023). Different infections use different modes of transmission.
These modes include:
The infectious agent spreads through large respiratory droplets in the air, which are then breathed in by another person. These droplets are released when an infected person coughs, sneezes or talks, travelling a short distance (about one metre) before falling to the ground. They may also contaminate nearby surfaces. If an uninfected person makes contact with these contaminated surfaces and touches their eyes, nose or mouth, this may also result in transmission.
Similarly to droplet transmission, the infectious agent spreads through respiratory droplets from an infected person. However, these droplets are much smaller in size, meaning they can stay suspended in the air for a longer period of time and be dispersed by air currents. Consequently, the air of the room of someone who has an airborne infection may be contaminated.
The infectious agent is spread through direct contact with an infected person/animal or their bodily fluids. This can include:
An uninfected person makes physical contact with a contaminated surface. A common example of this is faecal-oral spread, where tiny amounts of faeces from an infected person’s hands contaminate another surface. An uninfected person makes contact with this surface and then touches their mouth, allowing the particles of faeces to enter their body.
Parasites such as mosquitoes and ticks may be carriers (‘vectors’) for other disease-causing pathogens such as malaria.
Some infectious agents can contaminate food or water, resulting in infection when it is consumed.
(SA Health 2022a, b; Ministry of Health 2021; Mayo Clinic 2022; Government of Nunavut 2014)
The means through which the infectious agent enters the new host. Depending on the mode of transmission, this can occur via:
(Reuter 2023; NFID 2016)
An uninfected individual who is susceptible to developing an infection when the infectious agent enters their body. Depending on the individual and the invading pathogen, they may be able to fight off the infection. Those who are more susceptible include:
(Reuter 2023)
In order to manage and prevent the spread of infectious diseases, it’s crucial to interrupt the chain of infection at any of the six links.
The specific preventative measures used will depend on the pathogen and its mode of transmission. However, the following list offers some suggested strategies for breaking the chain of infection at each link.
Note: Infectious agents may still be present even if preventative measures are taken. However, the more measures implemented, the easier it will be to interrupt links of the chain. Prevention is most effective when a combination of measures is used.
Stage of the chain | How to disrupt it |
---|---|
1. Infectious agent | |
2. Reservoir |
|
3. Portal of exit |
|
4. Mode of transmission |
|
5. Portal of entry |
|
6. Susceptible host |
|
(APIC 2016)
Question 1 of 3
True or false: Bacteria need a living host to survive.