Can you transmit COVID-19 even without feeling sick?
The origin of the rumor
As we learned very early on at the start of the pandemic, some of the infected people are “asymptomatic” – which means that they have no apparent. From there, an idea continues, even today, to circulate through social networks: the asymptomatic would not be contagious. And this assertion becomes all the more a pretext to contest health measures, as asymptomatic people represent a significant proportion of infected people.
It should also be remembered that contradictory messages circulated on this subject in the first from . Although as early as January 2020, scientists had a hunch that people without symptoms could transmit the , the authorities took to incorporate this fact into their recommendations. This resulted in what was interpreted, not always wrongly, as a waltz-hesitation, which fed skepticism.
Yes, asymptomatic people are contagious
Scientists agree and well for a year on the fact that asymptomatics can be vectors of transmission of COVID-19. The unknown is the exact transmissions caused by them. It seems that this is less frequent than with very sick people, who, for example, will spread the disease more easily coughing. But measuring with precision the contribution of asymptomatics to the epidemic remains difficult even today. On their page dedicated to the modes of transmission of the virus, the of diseases of the United States (CDC) report that asymptomatic and presymptomatic patients are responsible for more than 50% of transmissions.
In a review of the literature published in December 2020, the from of Quebec also concluded that asymptomatic people can indeed transmit the infection.
Other more recent studies abound in the same . A published on February 27 in on a vast program of in Luxembourg concludes that the risk of transmission in asymptomatic people exists, even if it is lower. These results are consistent with those of 13 other studies, adds a comment in
Part of the confusion is due to the semantic nuances, which separate asymptomatic (who never develop symptoms) and presymptomatic (who will get sick a few times). later), or even oligosymptomatic (which have symptoms so weak that they continue to function as if nothing had happened). However, if this distinction is important for research, it is less so in practice, when it comes to popularizing the importance of health measures: whatever the distinction, someone who does not feel sick can transmit the virus.
A revived rumor
In December 2020, a study of of Florida published in the was widely shared by opponents of health measures: their interpretation was that this study would have shown that asymptomatic people never transmit COVID. However, as the authors of the study themselves must have recalled, this meta-analysis was interested in the transmission of COVID within a and not in the community. In addition, the study concluded that there was indeed a risk of transmission by asymptomatic people: it was just that he was thinner.
A crucial figure: the asymptomatic
Finally, the difficulty in measuring the contribution of asymptomatic patients to comes from the fact that we do not know what is the exact proportion of asymptomatic, since they are not systematically tested. However, this is crucial information: even if asymptomatic people transmit the disease “less”, the more there are, the greater their impact. It is estimated that 30 to 50% of Covid-19 cases are asymptomatic.
There is no doubt that a large number of asymptomatics can transmit the virus. It remains to be seen how many can, if we want to be able to accurately measure their contribution to the epidemic.