Following a number of recent global news stories about viral load and its impact on Coronavirus (COVID -19) patients;

Michael Breen, Director of Infectious Diseases at GlobalData, a leading data and analytics company, offers his view on this phenomena and how concerned we should be about it;

“A recent study from China supports a higher viral load being associated with more severe disease, and that viral load could be useful in stratifying patients for assessment of disease severity and prognosis.

“There are two factors that will likely influence your viral load: initial exposure, and patient factors such as age and immunocompetence. For the vast majority of patients, initial exposure to high viral loads is extremely unlikely, and patients with severe disease are frequently hospitalized. With around 80% of admitted patients with severe disease (and high viral loads) being in the intensive care unit (ICU), and much of the remainder also being hospitalized but not in the ICU, these patients are accordingly – at times of peak viral load – not likely to be in the community spreading disease.

“Thus, healthcare workers are likely to be the group at greatest risk of a high initial bolus of virus, while the general population would contract the infection through a significantly smaller load.

“As older patients are disproportionately affected by COVID-19; we can probably assume that initial viral doses are probably not the driver of most disease we’re seeing, as there is little reason why we would be able to conclude that they are disproportionately exposed to high viral doses. Thus, there is likely something inherent to this older patient group that may allow for a higher load post-infection, rather than at the time of infection, which is driving more severe disease.

“For cases of severe disease in non-healthcare workers, we should likely be thinking of patient-specific factors, which allow for high viral loads, or factors such as our own responses to the infection driving more severe disease. Obesity, smoking and even stress can be factors that allow for infections to take hold. Inflammatory responses, and sometimes (severe) overreactions, are what can trigger steep differences between disease severity and outcome, as is well-documented in sepsis.

“So we really need to distinguish between high initial viral dose and viral load, and while high initial viral doses may be associated with worse disease, these cases are likely rare.”