Sunday, May 26, 2024

Yes, people without symptoms can be contagious

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Maria Gill
Maria Gill
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This article is part of a column Rumor detectorClick here for other texts.

The origin of the rumor

As we learned very early in the start of the pandemic, some infected people are “asymptomatic” – meaning they have no noticeable symptoms. From there, the idea continues, to this day, to spread across social networks: non-infectious symptoms will not be contagious. This confirmation becomes a pretext to challenge health measures, as people without symptoms represent a large proportion of the infected.

We should also remember that Conflicting messages It circulated on this topic in the early months of the pandemic. although From January 2020And scholars He had an intuition People without symptoms can transmit the disease, authorities say Took time to blend in This fact is in their recommendations. This resulted in what is interpreted, not always incorrectly, as a Waltz frequencyWhich fueled suspicions.

Yes, people without symptoms are contagious

Scientists agreed for a year on the fact that asymptomatic could be a vector for transmission of COVID-19. The unknown variable It is the exact percentage of transmissions that cause it. It seems logical that this is less common than people who are very ill, for example they would spread the virus more easily by coughing. But precisely measuring the contribution of asymptomatic to an epidemic remains difficult today. On their page Dedicated to patterns of virus transmission, the United States’ Centers for Disease Control (CDC) states that asymptomatic or asymptomatic patients Will be responsible More than 50% of the transmission.

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In a literature review published in December 2020, Quebec Institute of Public Health He also concluded that asymptomatic people could transmit the infection.

Many other, more recent studies are in the same direction. Search Posted on February 27 in The scalpel In a large screening program in Luxembourg, it was concluded that the risk of transmission among people without symptoms of the disease is present, even if it is lower. These results are consistent with those of 13 other studies, adds A. Comment in The scalpel.

Semantic differences

Part of the confusion explained Semantic differences, Which separate symptoms (those who never show symptoms) and precede symptoms (who will get sick after a few days), or even those with few symptoms (those with symptoms so weak that they continue to function as if nothing happens). Now, if this distinction Important to researchIt is less important in practice, when it comes to generalizing the importance of health measures: regardless of distinction, a person who does not feel ill can transmit the virus.

A renewed rumor

In December 2020, Study from the University of Florida Posted in Journal of the American Medical Association, Opponents of the health measures shared widely: their explanation was that this study was going to show that people without symptoms never transmit COVID. However, as the study authors themselves I have to mentionIn this meta-analysis, we looked at the transmission of COVID within the home rather than in the community. In addition, the study concluded that there was indeed a risk of transmission by asymptomatic people: it was just the thinnest.

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Crucial figure: a number of closeness

Finally, the difficulty in measuring the contribution of asymptomatic patients to the infection stems from the fact that we do not know what the cause is. The exact percentage of asymptomatic, As it is not systematically tested. However, this is important information: Even if people without symptoms transmit “less” disease, the more often they are, the greater their effect. We think so 30 to me 50% Of Covid-19 cases do not show symptoms.


There is no doubt that a large number of syndromes can transmit the virus. It remains to be seen how many people can do so, if we are to be able to accurately measure their contribution to the epidemic.

Photo: Anna Kovtun / Pixabay

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