COVID-19: How to break the chain of infection

Sabina Muminović Last updated: 27 October 2023

It’s been more than one year since COVID-19 first reached public debate. Now, we hear something regarding it every single day! It can feel overwhelming and can cause unpleasant feelings on a daily level.

That’s why it’s essential to break this chain – not only of daily discussions about sickness and disease but breaking the chain of infection as well. This way, you can keep yourself and others healthy, which is vital: especially nowadays.

Dive deeper and learn the links of the chain, what you can do to break them and how your genes can affect the course of COVID-19.

In this article

What is the chain of infection?
Which are the links?
How can we break the chain?
What role do genes play?
Learn if you’re susceptible to severe COVID-19

What is the chain of infection?

The chain of infection is a process of an infectious disease spreading from one person to another. The process consists of six links, and the transmission can only succeed when all six of them are complete.

In principle, the ‘chain of infection’ paradigm applies to tackling healthcare-associated infections (HAIs), but it’s useful when thinking about stopping COVID-19 in non-healthcare settings too. Infection prevention and infection control principles aim to break the links in this chain, as it can stop the spread of infection.

Chain of infection

Which are the links?

There are six links – and the more links in the chain you can break, the better.

Here we go:

1. Disease microorganisms or germs

The first chain of the link, scientifically called the agent, consists of the pathogens that cause diseases.
Most commonly, these are bacteria, viruses, fungi, or parasites.

2. Reservoir

Sometimes called the source, the reservoir is a host which allows the pathogen to live, grow, and multiply.
The host can be a person, an animal, or the environment. As we know, a person may have a disease but is not symptomatic or ill. We call this person a carrier.

3. Mode of escape or portal of exit 

SIt refers to the route by which the infectious microorganisms escape or leave the source. For example, pathogens that cause respiratory diseases, such as COVID-19, usually exit through the respiratory tract (coughing and sneezing).

Other portals of exit include the intestinal tract (rectum), urinary tract, blood, and other body fluids.

4. Mode of transmission

There are different classifications for modes of transmission. We will look at one of them.

Get ready; this is a complicated one!

Since microorganisms cannot travel independently, they require a vehicle to carry them to other persons and places. Breaking the chain at this link is one the most critical ways to interrupt the spread of infection, as it can be most successful.

Four main routes transmit microorganisms:

• Contact

There are two types of contact transmission.

Direct contact means the physical transfer of an infectious agent from a reservoir to a susceptible host. Direct contact transmission involves actual physical contact between an infected subject and a susceptible subject (e.g., kissing, hugging, or sexual intercourse for sexually transmitted viral diseases).

Indirect contact means contact between a person and a contaminated object. It’s often a result of unclean hands contaminating an object or environment (means any surface or piece of medical equipment). The microorganism remains on this surface to be picked up by the next person who touches it.
Concrete examples of indirect contact are touching the door handle and then touching your eyes, touching the shopping cart or elevator buttons, handling cash, and then touching your face.

We’re pretty sure you’ve done one of these things before – that is why it’s essential always to wash your hands!

If you are still doubtful of the handwashing effects, check out the numbers.

Educating the community about handwashing:

• reduces respiratory illnesses, like colds and COVID-19 in the general population by 16–21%, and
• reduces the number of people who get sick with diarrhoea by 23–40%!

Person washing its hands

Droplet transmission

Droplet spread refers to relatively large, short-range aerosols produced by sneezing, coughing, laughing, or even talking. Droplet spread is classified as direct transmission because droplets containing microorganisms are propelled through the air and land on another person. They enter through the portal of entry. These microorganisms are relatively large and travel only short distances (up to 6 feet/2 metres).

Examples of diseases transmitted from an infectious patient to a susceptible host by droplet spread are whooping cough and infection with meningococcus bacterium, causing meningitis.

• Airborne transmission

Microorganisms travelling by air!

The residue of evaporated droplets from an infected person remains in the air long enough to be transmitted to the respiratory tract of a susceptible host. The pathogens can travel alone or wrapped in dust particles. If microorganisms are carried in this manner, they can remain suspended in the air for long periods.
Consequently, pathogens can contaminate the air in the room.

One more to go!

The fourth route of microorganism transmission is the common vehicle.

Common vehicle transmission refers to microorganism’s transmission through a contaminated source – food, water, medications, medical devices and equipment.

These “common vehicles” potentially expose many people and can be responsible for widespread disease transmission.

As you can see, an infectious agent can be transmitted from its natural reservoir to a susceptible host in a myriad of different ways. We hope this helps you better understand the paths microorganisms can take to enter your body and make you sick.

5. Portal of entry

The fifth link in the chain is the path microorganisms use for getting into the new host. It can happen through:

• inhalation,
• ingestion,
• absorption,
• broken skin,
• open wounds,
• respiratory tract,
• introduction by medical procedures (catheters and lines),
• or most usual: eyes, nose or mouth (your mucous membranes).

There are several strategies to break the chain at this link. For example; bed nets are used to protect sleeping persons from being bitten by mosquitoes that may transmit malaria. A dentist uses a mask and gloves to protect himself from a patient’s blood, secretions, and droplets.

Wondering why everyone is telling you to wear a mask?

The fifth link of the chain, mode or portal of entry, can be broken with this step. If you wear a mask, you cannot inhale the pathogens, and you have successfully broken the chain of infection. Yay you!

Did you know that the effectiveness of masks can range from 0 to 80 percent, depending on material composition, number of layers, and layering bonding? The N95 mask, which is generally reserved for health professionals, can filter out at least 95% of very small particles!

Reusable fabric face masks are definitely an environmentally friendlier version of disposable masks, but make sure you choose the one that offers the best protection. Based on the latest research, the CDC recommends masks:

• made of tightly woven fabrics, such as cotton and cotton blends,
• made of two or three fabric layers, and
• that fit snugly over your mouth and nose.

And don’t forget to wash them daily!

6. Susceptible host

The future host is the person who is next exposed to the pathogen.

The microorganism may spread to another person but does not develop into an infection if the person’s immune system can fight it off! However, they may become a ‘carrier’ without symptoms, able to be the next ‘mode of transmission’ to another ‘susceptible host’.

Once the host is infected, he/she may become a reservoir for future transmission of the disease. That’s when the chain of infection can start again.

How can we break the chain?

WIf you interrupt it at any link, the chain will break. There will be fewer infections, which ultimately is our common goal. The more measures we implement, the easier it will be to interrupt links of the chain. Prevention is most effective when we use a combination of measures.

Our recommendations seem general, but they can make a difference.

You can help break the chain by:

• cleaning your hands frequently

As mentioned, thoroughly washing hands with soap and water is one of the best ways to prevent you or someone you know from getting infected. Wash your hands frequently and help to remove potentially harmful microorganisms from your hands and stop the spread of infection.

• covering coughs and sneezes

As droplets from coughs and sneezes travel up to 2 metres, these simple steps can reduce the spread of COVID-19. Practice cough and sneeze etiquette:

Cover your mouth and nose with a tissue when coughing or sneezing and dispose of the tissue. If you do not have a tissue, sneeze into your elbow rather than your hands. Wash your hands with soap and water immediately after coughing or sneezing.

Some other helpful tips are:

• staying home when sick,
• following the rules for standard and contact isolation,
• using personal protective equipment, such as clothes and masks,
• opening windows to let the fresh air in,
cleaning and disinfecting your environment and frequently used surfaces such as benchtops, desks, doorknobs, mobile phones, keys, and wallets.

Encourage other people around you to do it as well!

If you are a healthcare worker, you should always make sure to wear gloves and PPE when in a patient’s surroundings and clean high-risk areas to prevent any potential spread of the infection.
Even if you don’t work in healthcare, it’s still important to consider these safety measures and keep yourself and others safe – not only from COVID-19 but from other diseases as well.

What role do genes play?

If the chain of infection completes and the disease starts to develop, your genes will be involved in how your body will respond to the infection.

Recent studies have identified genetic variants associated with severe COVID-19 symptoms when infected. Based on the genetic profile, we can predict the likelihood of severe COVID-19 symptoms.

Many people infected with SARS-CoV-2 show mild to moderate symptoms (or even no symptoms at all).

You might even know someone who was positive but had no visible symptoms! As we briefly mentioned before, these people are called carriers. However, the most common signs of COVID-19 are fever, dry cough, and fatigue. Some other typical symptoms include aches and pains, sore throat, loss of taste or smell, diarrhoea, headache, conjunctivitis, skin rash, and discolouration of fingers or toes.

If you are unlucky, you may suffer from more severe symptoms, such as difficulty breathing or shortness of breath, chest pain or pressure, and loss of speech or movement.

But does this actually depend on luck?

Nope, not really.

The risk factors of developing the severe form of COVID-19 include:

• age,
• underlying health conditions (cardiovascular disease, chronic lung disease, sickle cell disease, diabetes, cancer, obesity, or chronic kidney disease),
• pregnancy,
• smoking,
• being a transplant recipient,
• or undergoing immunosuppressive therapy.

And your genes!

Research has shown that the severe form of COVID-19 relates to two crucial biological mechanisms:

• innate antiviral defences, which are essential in the early stages of the disease (and involve the IFNAR2 and OAS1 genes);
• inflammatory lung injury (involving DPP9 and TYK2 genes) is crucial in the later stages of life-threatening COVID-19.

How you get through COVID-19, what it depends on, and how you can influence the outcome is one of the giant puzzles of the pandemic. Our analysis can help you determine your susceptibility to developing severe COVID-19 symptoms.

If your immune system is strong enough, it can fight the infection more successfully!

A healthy lifestyle is crucial for an effective immune system. Try implementing regular exercise in your day, eating fresh and balanced meals, and maintaining a healthy weight. Learn more about how you can boost your immune system with healthy habits here.

Learn if you’re susceptible to severe COVID-19

Wondering how we can determine this with just one test?

Your genes help us do it! Plunge into the world of genetics with us for a minute.

A specific combination of genetic variants (known as a haplotype) in a region of chromosome 3 covers a cluster of six genes – SLC6A20, LZTFL1, CCR9, FYCO1, CXCR6, and XCR1.

We associate this particular gene cluster with an increased risk of developing severe COVID-19 symptoms (including respiratory failure), which could require hospitalisation. Research has shown that around 16% of people in Europe and 50% of people in South Asia carry it.

However, another haplotype on chromosome 12 protects against severe COVID-19!

Young woman meditating

This DNA segment covers the genes OAS1, OAS2, and OAS3, which encode proteins that produce so-called ‘short-chain polyadenylates’. Research has shown that the relative risk of needing intensive care can be reduced by approximately 22% per copy of this haplotype! Besides COVID-19, it is protective against other RNA viruses, such as the West Nile virus and hepatitis C.

Other genes, such as DPP9, TYK2, IFNAR2 and the APOE gene, also play an important role in your chances of developing the severe form of COVID-19 symptoms.

Don’t worry; you don’t have to remember all these names – we do it for you.

Based on your DNA, we can assess the likelihood of suffering from a severe form of COVID-19. Nonetheless, even if you get a favourable result, it does not mean that you are immune to infection. Neither does it eliminate the possibility of severe COVID-19 symptoms, as genetics is only one of the factors influencing COVID-19 severity.

Find out how susceptible you are to developing severe COVID-19 symptoms based on your genetic predispositions here.

Get to know your Immune system! It can help you discover your genetic predispositions for ABO blood type, COVID-19 disease severity, susceptibility to SARS-CoV-2 infection, resistance to noroviruses and resistance to malaria (Duffy type). 

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