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Current Affairs

Viral load of SARS-CoV-2

Date: 11 April 2020 Tags: Miscellaneous

Issue

As we make more progress in the fight against the novel coronavirus, findings are emerging about the viral load of SARS-CoV-2.

 

Background

Identifying viral load patterns also helps researchers and scientists figure out the disease prognosis and assessing its severity.

 

Details

  • Viral load refers to the amount of virus in the body of a person who is infected and could determine how ill a person can get from the disease or how infectious the person may be.

  • In the case of COVID-19, however, it is not exactly clear if asymptomatic and symptomatic cases have different viral loads in their bodies.

  • It also cannot be said certainly if a high viral load translates to more severe symptoms for a person or if they are more contagious.

  • Some recent research points out that the viral load patterns of SARS-CoV-2 differ to that of SARS-CoV. In the case of SARS-CoV-2, the viral loads are known to peak around the time of onset of symptoms, whereas in the case of SARS-CoV, the viral loads peaked about 10 days after the onset of symptoms. In the case of MERS, the viral loads are known to peak around 14 days after the onset of symptoms.

  • The viral load profile of a particular pathogen can help in figuring out how to administer antiviral treatments to a patient, especially since there is no standard recommended treatment for COVID-19 as of now.

  • A study analysing the early phase of the outbreak in Lombardy, did not find a “significantly different” viral load in the nasal swabs of symptomatic and asymptomatic cases, which could mean that both have the same potential for transmitting the virus.

  • The study also maintains that the “limited number” of asymptomatic infectious cases that were identified through contact tracing may suggest they play a “minor role” in the overall spread of infection.

  • Another study observed the highest viral load in throat swabs at the time of symptom onset, from which they infer that a person’s infectiousness may peak on or before symptom onset.

  • They note that the viral load gradually decreased towards the detection limit at about 21 days after onset. There was no obvious difference in viral loads across sex, age groups and disease severity, they say.

  • In another study published in The Lancet, researchers note that the mean viral load in severe cases analysed by them was over 60 times higher than that of mild cases, which suggests that higher viral loads may be associated with more severe outcomes.

  • The research is still emerging and it cannot be said with certainty how viral loads of SARS-CoV-2 are associated with severe symptoms or how contagious the person is if they display higher viral loads. 

  • Broadly, a higher viral load may make the transmission of the virus easier and may mean more severe symptoms for the infected person. But research differs about the correlation of viral loads with age and it is also unclear if asymptomatic and symptomatic cases have different viral loads.