Covid-19: wearing a mask, viral load and seasonal flu

Almost 10 months after the discovery of the coronavirus, many questions still remain about the mechanisms of transmission of SARS-CoV-2.

MEHDI FEDOUACH / AFP

Text by: Simon Rozé Follow

5 mins

As European countries appear to be facing what looks like a second epidemic wave, many questions still remain about the mechanisms of SARS-CoV-2 transmission.

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Almost ten months after the discovery of the coronavirus, much has been written about how it is transmitted.

Numerous studies have been carried out since the start of the pandemic, some isolated, others not having been reproduced;

it is therefore sometimes complicated to navigate.

The prestigious journal

has therefore decided to take stock of all its knowledge and summarize precisely what we know about the mechanisms of transmission of Covid-19.

This is necessary compilation work, yet never done before. 

Today, the scientific community therefore knows that the virus can remain present and infectious for a period of 3 hours in the air and up to 3 days on plastic.

Nevertheless, if cases of contamination via infected surfaces have already been observed, the mechanisms of such an infection have never been really proven and its extent must be low.

The virus therefore penetrates mainly by air, thanks to postilions and probably smaller particles, aerosols.

This transmission is all the more frequent if people are close to each other, less than two meters, for a long time, in a room which is not ventilated.

It is also known that an infected person, whether or not they have symptoms, will be contagious three days before they appear and up to five days thereafter on average.

This contagiousness will then depend on the viral load, the quantity of virus in the body.

Wearing a mask to promote collective immunity?

The mask therefore prevents a certain number of contaminations, but also has other interests.

The

publishes this week a “ 

 ” in which the authors return to the concept of variolation.

This is not, however, a study, but an alert from researchers, who indicate to the community a lead that could be interesting to explore.

This returns to the concept of viral load: the authors indeed emphasize that according to the latest data available, the lower it is, the less severe the case of Covid-19 will be.

In addition to contagiousness, this viral load therefore has a link with the severity of the disease.

They also write, that still according to current knowledge, if it fails to prevent an infection,

will then limit the entry of viruses into the body of the newly infected person: his viral load will therefore be low.

People infected while wearing a mask will then more often develop mild or even symptom-free Covid-19.

Finally, the authors stress that these patients will always benefit from an immune response.

This is where variolation comes in.

This is a strategy used for centuries against smallpox until a vaccine arrived.

At the time, it was a question of weakly exposing healthy people to smallpox, so that they develop immunity at the cost of a mild illness.

The authors of this article estimate that for the Covid-19, the generalized wearing of the mask could play this role and would allow progress towards collective immunity while awaiting the arrival of a vaccine.

They therefore call on the community to step up research work to verify this hypothesis.

The seasonal flu epidemic worries

Wearing a mask finally has another advantage.

The American Center for Disease Control (CDC) teaches us in its

that it can play a role against epidemics of seasonal flu.

The researchers noted that in the United States, as of mid-March 2020, the incidence of the disease had greatly decreased compared to previous years.

According to them, the reason is simple: it was during this period that the barrier measures against Covid-19 came into force.

Social distancing and wearing a mask are therefore also effective against the spread of influenza.

This was suspected because the two viruses share the same mode of transmission.

It is now observed.

This is good news because the occurrence of a new epidemic of seasonal flu this winter is worrying.

The coexistence of the two diseases risks causing heavy pressure on hospitals, worsening the cases of patients suffering from an infection with the two viruses or even diagnostic difficulties because their symptoms are similar.

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