The science behind coronavirus: An easy guide

It's a time of high anxiety and confusion for many across the globe. While many of us wait in lockdown, scientists around the world are gathering and sharing data on COVID-19 at a furious pace. Every day, new updates and findings emerge in the media, and the scientific references can be challenging to comprehend.

To help get you through the pandemic, UNSW virologist, Dr Sacha Stelzer-Braid, answers a spectrum of questions on the science behind this new coronavirus. 

What is coronavirus, and has there been one before?

Coronavirus is the name for a family of viruses. 

There are many strains of coronavirus, from the mild to more severe. Some examples of more severe cases prior to this pandemic include Severe Acute Respiratory Syndrome (SARS-CoV-1) which emerged in Asia in 2003, and Middle East Respiratory Syndrome (MERS) first identified in 2012. 

Though new and deadly in around <1% of cases in Australia, SARS-CoV-2 is not the first coronavirus humans have encountered, it is simply the most recent coronavirus to emerge.

In addition to those mentioned above, there are four known coronaviruses which circulate among humans. Three of them cause about 15% of colds, while the fourth coronavirus is responsible for about 2% to 5% of cases of croup (a disease mainly in infants and young children).

Why do some scientists refer to it as SARS-CoV-2 (as opposed to COVID-19 or coronavirus)?

SARS-Cov-2 stands for Severe Acute Respiratory Syndrome Coronavirus 2, and COVID-19 stands for Coronavirus Disease 2019—the year when it first emerged.

If we are being technical, SARS-CoV-2 (the species of virus) gives you COVID-19 (the illness). The World Health Organisation explains it as being the same way you would say that HIV gives you AIDS.

Of course, it does sound very technical and medical, so it is no wonder that most are sticking with ‘coronavirus’ as a broadly accepted term.

Where in the body does SARS-CoV-2 attack?

A person can become infected with a virus when they come into contact with the diseased particles, which then infiltrate our bodies, hijacking healthy cells and replicating rapidly. Where a virus replicates can dictate the infection’s symptoms.

The common cold-causing coronaviruses replicate in the cells lining the upper respiratory tract and prompt symptoms like sneezing and a runny nose. In contrast, SARS-CoV-2 primarily infects cells and replicates deep within the lungs, otherwise known as the lower respiratory tract. 

Is the lower respiratory tract more susceptible to damage than the upper respiratory tract? 

Generally speaking, a viral infection in the lungs is worse than an infection in the upper respiratory tract (affecting mostly the nose and throat), because of the potential for bacterial secondary infections in the lungs such as pneumonia. 

There is also increased possibility of long-term damage, for example, leading to asthma in the case of other respiratory viruses such as Respiratory Syncytial Virus (RSV). For those with pre-existing conditions that would make it more difficult to fight off bacterial infections and secondary diseases, this can be a dangerous combination.

How stable are coronavirus particles outside the body? 

A lot of people are anxious about touching door handles, receiving mail and shaking hands due to the unknown lifespan of SARS-CoV-2. So, how do coronaviruses withstand these surfaces?

All viruses are obligate intracellular parasites; in other words, they have to be inside a cell, such as a human, animal, plant or bacteria, in order to replicate. So, in general, they have a finite shelf-life outside the body.

However, viruses differ by their chemical composition. Coronaviruses are characterised by having a layer of fat (lipid) around their body (genes and proteins), which is called an ‘envelope’. The envelope is critical for the virus to enter a cell and is very susceptible to the sort of environments it can withstand. If the virus loses its envelope, it loses infectivity. 

Research on SARS-CoV-1 and MERS tells us that coronaviruses may exist for 24-48 hours outside the body. Further studies reveal that SARS-CoV-2 can survive for up to three days on hard surfaces but will decrease in infectivity over this time. The virus can be killed by washing hands for 20 seconds with regular soap (this breaks up the lipid envelope), or washing surfaces with detergent and hot water or diluted bleach.

We hope this summary has provided enough key information for you to better understand the conversations and decisions around COVID-19. If you have any further questions about the virus that our academic community can support with, please contact us.

Dr Sacha Stelzer-Braid is a Senior Postdoctoral Scientist in the Virology Research Lab at UNSW Sydney and Prince of Wales Hospital. She is currently working on studies involving whole-genome next-generation sequencing of SARS-CoV-2 and enterovirus from around NSW and assessing new point-of-care tests through the UNSW Centre for Research Excellence “Integrated Systems for Epidemic Response (ISER)”.