Since 2020, medical professionals across the globe have been tirelessly investigating all there is to know about COVID-19. From the viral load and how the disease is passed on through communities to the factors that increase the risk of severe illness, researchers have been synthesizing information that could aid in slowing the spread and lowering the death toll.
While there is still much we do not fully understand about COVID-19, including how it affects people differently and why, there are some new studies shining light on the viral load and its possible connection to severe COVID-19 cases. So what is the relevance of viral load in the severity of COVID symptoms, exactly?
What is viral load in terms of COVID-19?
A viral load in terms of any contagious disease is the amount of virus that can be found within the body at any given time. To check someone’s viral load, medical professionals will typically use blood, nasal swabs, or bodily fluids. However, the viral load of COVID-19 may not be as straightforward as it is with other types of infections. Different people have different viral loads, regardless of their vaccination status.
The key reason for investigating the viral load and how it appears in different people is to gain clarity on how the virus spreads and determine how it may be related to symptom severity. Is COVID-19 more severe in those with higher or lower viral loads? Does the viral load have anything to do with how symptoms present?
These are questions scientists have been aiming to answer since the onset of the pandemic. Even with a couple of years to investigate so far, the changing nature of the disease throughout this time, including several mutations, has made it difficult for researchers to come to a consensus.
How is the severity of a COVID-19 infection defined?
To understand the viral load and its connection to disease severity, it’s important to have an understanding of what exactly constitutes severe disease.
According to the National Institutes of Health, severe COVID-19 illness is defined as: “SpO2<94% on room air at sea level, PaO2/FiO2<300mm Hg, a respiratory rate >30 breaths/min, or lung infiltrates >50%.” Patients who fall under these categories are thought to experience rapid declines in health and should be put on oxygen immediately.
To put it in simpler terms: each person with a COVID-19 infection has to meet the above criteria in terms of oxygen saturation levels, ratio of arterial oxygen partial pressure, rate of breathing, and substances other than air that have gotten into their lungs.
Does high viral load typically mean more severe disease in other infections?
Typically, a high viral load is only indicative of how contagious a person is. That being said, in some cases, it can indicate when a person will have a more severe case of disease. When looking at an illness other than COVID-19, such as influenza, research has shown that different strains adhere to different rules in terms of disease severity and viral load.
For example, one study looked at viral load and hospitalizations with influenza and found that those hospitalized with influenza B had higher viral loads than those who were hospitalized with influenza A. However, this isn’t a way to determine COVID-19 severity and viral load, because it is a completely different type of virus.
Is there a relationship between the COVID-19 viral load and severity of disease?
It can be difficult to determine if there is a relationship between a person’s viral load and the severity of the disease, because research is seemingly mixed. For example, one study published in October 2020 found that the viral load is highly associated with an increased risk of disease severity. However, that study was done at the beginning of the pandemic and contains some limitations such as small sample size.
Newer research published in July 2021 found the opposite to be true: there was no association with a higher viral load and disease severity at all. The study does also mention that various other studies were completed previously that associated high viral load with mortality from COVID-19.
One of the most recent investigations, carried out in December 2021, presented inconclusive results when examining the connection between a higher viral load and COVID-19 severity. However, the research posited that age may be a factor when it comes to higher viral load and infection severity, because older patients were seen to have higher viral loads and more severe disease.
While the jury is still out when it comes to viral loads and disease severity, research will continue to investigate just what causes people to develop more severe disease when they contract COVID-19 – and hopefully how such cases can be reduced.