What is viral load and how does it affect the spread of coronavirus?
DEADLY coronavirus is continuing to spread with more than 400,000 confirmed cases around the world in 183 countries.
Most governments have now responded to the outbreak by enforcing lockdowns of their populations – with experts mentioning the impact of “viral load” in patients with more severe illness.
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But many people have been left asking what exactly is “viral load” and why it matters for Covid-19.
Here, with the help of experts, we take you through exactly what viral load is and it’s relationship to the new coronavirus, which has killed 434 people in the UK.
What is viral load?
The term viral load refers to the amount of viral particles present in a person’s body.
Professor Richard Tedder, Visiting Professor in Medical Virology, Imperial College London, says that it usually refers to the amount of measurable virus in a standard volume of material – typically blood or plasma.
He added: “It is very commonly used to define how HIV responds in a patient to antiviral drugs.
“A patient taking such drugs would be pleased to know that their ‘viral load’ is reduced.”
Why does viral load matter for coronavirus?
Some early research from China has suggested people who are exposed to a larger viral load could experience worse symptoms when they become ill with coronavirus.
According to Dr Edward Parker, a research fellow at the London School of Hygiene and Tropical Medicine, this is also the case for viruses such as severe acute respiratory syndrome (SARS) or the flu.
When someone is infected with a virus, it replicates in their body’s cells.
Analysis published by The Lancet medical journal claims viral load in Covid-19 patients is highest at the start of their illness.
They have pointed out that this could account for the fast-spreading nature of the coronavirus outbreak.
How can you limit viral load?
Currently, there is no vaccine to protect people against the virus.
Antibiotics do not help, as they do not work against viruses – only bacteria.
The NHS says that treatment aims to relieve the symptoms while your body fights the illness.
Therefore, until scientists develop a treatment or vaccine, countries around the world are being forced to impose strict conditions on their populations to try to limit the spread of the bug.
Boris Johnson announced on Monday, March 23, that all UK residents must stay at home to stop the spread of coronavirus.
The PM got tough with the public, urging them to stay indoors to save lives and protect the ailing National Health Service.
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Dr Parker say it is “crucial” for people to limit their exposure to coronavirus.
He said: “The amount of virus we are exposed to at the start of an infection is referred to as the ‘infectious dose’.
“For influenza, we know that that initial exposure to more virus – or a higher infectious dose – appears to increase the chance of infection and illness.
“Studies in mice have also shown that repeated exposure to low doses may be just as infectious as a single high dose.
“So all in all, it is crucial for us to limit all possible exposures to Covid-19, whether these are to highly symptomatic individuals coughing up large quantities of virus or to asymptomatic individuals shedding small quantities.
“And if we are feeling unwell, we need to observe strict self-isolation measures to limit our chance of infecting others.”
What does that mean in practice?
With the amount of virus in your blood at first infection directly linking to the severity of the illness you will suffer, it is obviously best to reduce the risk of exposure.
For example, if you are in a restaurant or another crowded space and a large number of people are infected with coronavirus but not showing symptoms, you will be breathing in a lot of respiratory droplets which are thought to spread the disease.
This will mean you will absorb a high viral load, which could be so great as to overrun your immune system and cause serious illness.
On the other hand, if you sit with only one infected person, you would get a smaller viral load and your immune system will have a better chance of fighting off the bug.
Experts claim this is why coronavirus is most widespread in London, where people are more likely to gather in big groups in crowded spaces – such as the tube – and got a large initial viral load.
They could then have gone home and infected their family and friends, if they did not follow government advice on social distancing.
What about shared houses?
The government says if someone in your household believes they have coronavirus they should separate themselves from other people in the house and stay in a designated ‘sick room’.
If you live in shared accommodation with a communal kitchen, bathroom and living area, they should stay in their room with the door closed, only coming out when necessary.
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In particular, vulnerable individuals (such as the elderly and those with underlying health conditions) should move out of shared homes, to stay with friends or family for the duration of the home isolation period.
If you cannot move vulnerable people out of your home, make sure the sick person stays away from them as much as possible
This is because if those infected all sit in one room together, you could increase the viral load for all of you and increase the severity of illness; as well as infect those who might not yet have caught coronavirus.