How is coronavirus transmitted? The answer is a long way from tre.

The assertion was growing that the 2019-nCov coronavirus could be transmitted by completely asymptomatic individuals. Except the main study on this subject… is wrong. The debate is not settled.

The outbreak of the new coronavirus emerged more than a month ago, at the end of December 2019. As the real-time map of the spread shows, as of January 5, 2020, the death toll is 25,500 infected people, 493 deaths and 921 recoveries. Faced with such figures, a question obsesses both the public and scientists: how is 2019-nCov transmitted between humans?

Let us first recall that this new coronavirus triggered what is still, even today, an epidemic. This is not a “pandemic”. Human-to-human contamination occurs mainly in the outbreak of the virus in China. Globally, and with no changes for the moment, 2019-nCov remains relatively under control. The situation calls for vigilance, but not catastrophism.

In addition, the coronavirus is the subject of very active research by many laboratories around the world. And the good news is that scientists can both sequence the virus’ genome and grow the strain in the lab, which helps them better understand it. As with any research that is in process, some results may be contradictory. In any case, there may be a debate in the scientific community. This is the case for the modalities of coronavirus transmission: a study that had become very important has just been refuted by another study.

  • Read more: Coronavirus: laboratory culture and sequencing are possible, and that’s a good sign

Coronavirus nCov-2019 (illustration). // Source : Numerama / Claire Braikeh

“No doubt” about transmission without symptoms? Not really.

By January, the information had spread and was taken almost for granted: asymptomatic people could not only still be infected with the coronavirus, but could also be contagious. This would represent one of the most complex epidemiological situations for health authorities to manage, as it would be a major obstacle to diagnosing infections and curbing the epidemic.

This idea was supported by a study published on January 30 in The New England Journal of Medicine. It focuses on the first four people who were infected in Germany. The local infection is believed to have originated from a woman returning from Shanghai who infected three colleagues at a time when, according to the study, she was doing well. For the authors, these cases confirmed by observation the transmissibility of the coronavirus in people without apparent symptoms. The conclusion of this research had even led Anthony Fauci, director of the American Institute of Allergic and Infectious Diseases, to declare to CNN that there was “no doubt” about this mode of transmission.

A perhaps somewhat hasty statement: for there to be a complete absence of doubt, there must be a body of evidence confirmed almost unanimously by a large number of studies. However, a new research paper published on Monday, February 3 in Science, strongly challenges the January 30 study.

One essential source was missing: the patient involved in the study…

This recent article in Science shows that the study it challenges made a most fundamental mistake: the authors relied on secondary sources, namely the accounts of other patients… but not that of the woman herself who had just returned from Shanghai.

Shortly after the publication of this study, the German health authorities contacted the original patient. She did tell them that she had symptoms upon her return to Germany – muscle aches and fatigue. Her colleagues were probably unaware of her condition because she had taken paracetamol. The author of the article in Science adds that the Robert Koch Institute – the German institution responsible for disease control and monitoring – alerted the World Health Organization and sent a letter to the New England Journal of Medicine to point out the error in the study.

We must be careful with our words

Virologist Christian Drosten, who was involved in the flawed study, says in Science that he feels “bad about how it happened” but does not think “anyone is at fault here“. Above all, he regrets that the publication of the study, with one source missing, was caused by a runaway phenomenon: “The woman could not be reached at first and people felt that this had to be communicated quickly. “Michael Hoelscher, also a stakeholder in the study, laments the global pressure to publish too early.

But this lack of an essential source, in a context of crisis, is causing an outcry in the scientific community. “Asymptomatic means no symptoms, zero. It means you’re feeling good. We have to be careful with our words,” says Isaac Bogoch, a Canadian infectious disease specialist interviewed by Science.

What conclusion can we draw from this?

That the study published in The New England Journal of Medicine is erroneous seems fairly certain given the material in Science, as well as the comments of some of the authors of the study itself. Does that mean the conclusion is entirely wrong? Is the coronavirus transmitted from person to person even in asymptomatic individuals? From the point of view of strictly scientific observations, we don’t really know. There’s a lack of evidence.

Transmission on an asymptomatic basis probably plays a minor role.

It remains likely that the answer is yes, according to information disseminated by Chinese health authorities since the peak of the epidemic. But, as noted by Science, the World Health Organization considers that this type of transmission on an asymptomatic basis plays a “minor role” in this case. Emphasis on it, moreover, in the absence of substantial evidence, is therefore unnecessary.

The drift illustrated by this erroneous study is that of a too frantic circulation of information on this subject. This is precisely what the WHO is denouncing, calling for caution about what the organization calls “infodemia”, which has accompanied the coronavirus epidemic for the past few weeks Between the surplus of information, the circulation of false information, preconceived ideas and conspiracy theories, it seems necessary to calm this global panic somewhat in order to remain rational – all the more so as bad information can have a negative impact on research and solutions, as the WHO Director herself points out.

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