Coronavirus is continuing to spread with more than 400,000 confirmed cases around the world. But why is the response of governments to enforce lockdowns of their populations? And what does “viral load” have to do with it?

What is viral load?

Simply put, viral load is the total amount of a virus a person has inside of them.

It usually refers to the amount of measurable virus in a standard volume of material, such as blood or plasma.

The term is very commonly used to define how an HIV patient responds to antiviral drugs.

For example, a patient who responds well to such drugs would see their viral load reduced.

Why does viral load matter for coronavirus?

COVID-19 is the disease that develops from coronavirus.

According to Dr Edward Parker, a research fellow at the London School of Hygiene and Tropical Medicine, early reports from China suggest that – when it comes to COVID-19 – the viral load is higher in patients with more severe disease.

This is also the case for viruses such as 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 suggests viral load in COVID-19 patients is highest at the beginning of their illness.

This could account for the fast-spreading nature of the pandemic.

So, how do you try and limit viral load?

Antiviral drugs used to treat the flu do not work for COVID-19.

Therefore, until a treatment or vaccine is developed, countries around the world are imposing stringent conditions on their populations to try to limit the spread of coronavirus.

The UK is, in effect, on lockdown with people being told to stay at home.

It is “crucial” for people to limit their exposure to coronavirus, according to Dr Parker.

“The amount of virus we are exposed to at the start of an infection is referred to as the ‘infectious dose,'” he said.

“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?

So, if the amount of virus in your blood at first infection directly relates 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 pub or another crowded space and a large number 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.

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