A “high” viral load even in asymptomatic people

Genetic traces of the coronavirus are believed to be almost as important in people infected with COVID-19, whether or not they are suffering from the symptoms of the disease, according to a South Korean study.

Scientists at Soonchunhyang University in Seoul analyzed data from 303 patients infected with COVID-19 who stayed during the month of March in a temporary isolation center established on the outskirts of the South Korean capital.

During their isolation, 89 people (29.4%) never developed symptoms – although they were diagnosed with COVID-19 positive – and therefore fall into the “asymptomatic” group.

In addition, 21 people (6.9%) showed no symptoms when they arrived at the center, but developed them later. They were therefore presymptomatic.

All other individuals had symptoms upon arrival.


The patients were generally young adults with no other health problem. All were tested periodically on the nose, throat and saliva to check for the presence of the virus.

The most astonishing result is that the viral load of asymptomatic patients was “similar” to that of symptomatic patients. The study appeared this week in the journal JAMA Internal Medicine. Another interesting fact: asymptomatic people healed slightly faster than others, receiving a negative first result on average on day 17 of their isolation, compared to days 19 or 20 for those with symptoms.

The researchers characterize the viral load found in infected and asymptomatic people “high”, suggesting that they “could be a key factor in the spread in the community”.


However, they acknowledge that their study “was not designed to determine” and therefore do not provide a definitive answer to this question.

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Indeed, the scientists were not able to do the data collection themselves, but instead analyzed the results of 1886 tests that were requested by the medical staff who were at the bedside of the 303 patients. They were therefore not able to verify whether the genetic material of the virus that was detected was infectious or not, since the method used detects the virus regardless of whether it is alive or dead.

Wider epidemiological and experimental studies will be needed to establish with certainty the risk of contagion posed by asymptomatic people, the researchers write.

According to them, a precautionary principle should apply and intensive screening of the population and contact tracing should be encouraged to help trace and isolate silent carriers of COVID-19.

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