Covid: what we know and still don’t know about the virus, one year on

Published by Cécile D. · Photos by Rizhlaine F. · Published on 7 April 2021 at 14h09 · Updated on 7 April 2021 at 16h38
Where does it come from, how did it contaminate the entire planet in a matter of months, how to get rid of this? The Covid-19 raised many questions and some of them remain answerless. What do we know about the virus that changed our lives in less than a year? Keep reading to find out more.

A third lockdown, closed schools and stores, cultural places, bars, and gyms that remained empty for months… It is hard to think the pandemic will end soon now. Even though in France, we feel like stuck in a time breach since March 2020, it feels good to list the breakthroughs amid the pandemic and how Covid-19 treatments improved.

Scientist communities from all over the world have been working on this virus for months. Such work, this unparalleled teaming of brains, enabled to make research move to an incredible speed. Institut Pasteur Virus and Immunity head manager Olivier Schwartz told France Info the number of scientific publications about coronavirus is breaking a record. “If I type Covid on PubMed – a website listing all scientific articles – I get 12,000 articles listed excluding all articles in pre-publication. As a comparison, for AIDS, there are 380,000 namely three times more with four decades back. Huge progress on understanding the virus, its functioning, its structure and the way it enters the organism, and how it spreads in infected cells have been made”, Schwartz says, delighted.

The arrival of the variants also shone a new light on how the virus mutates. “The virus happened to be subject to selection pressure, that is to say, it had been faced with immunized populations, whether because they have been infected already, or they have been vaccinated. To continue, it ensured it could be more infectious in order to get a selective advantage enabling it to better spread amid the population”, the professor goes on.

Therefore, the virus managed to quickly and effectively evolve since variants are now the most common strains in France.

Covid-19 is a virus that is mostly airborne through aerosols and droplets. This is why it is crucial to wear a mask and ventilate closed places. Paris Saint-Louis hospital infectious disease specialist Anne-Claude Crémieux reminds on France Info that “the extent of aerosols explains the supercontaminations that occurred in closed and poorly ventilated places. […] When it came to modes of transmission, first contamination through hands, objects have been overestimated, and airborne contamination underestimated”.

Her peer, Montpellier CNRS fluid mechanics searcher Simon Mendez adds that we now know “airborne contaminations in a room can occur in distance greater than one or two meters and in longer times we thought at first. We also know there are big variations from one moment to the other, depending on the stage of the disease and from one person to the other. If nine people contaminate none, and one person contaminates ten, the disease reproduction rate will be equal to 1 [the threshold beyond which it keeps on spreading]. This is also why the disease is hard to handle, it is not even”.

What about symptoms?

What made it difficult to detect and attend to the disease at the beginning of the epidemic is that it can seem different depending on people infected. Loss of smell and taste, breathing failures, or less worrying symptoms such as fever, cough, headaches, sore muscles… Covid-19 can be found in more or less severe forms and can often be mistaken for other diseases.

Furthermore, scientists are now aware the virus can spread between people 48 hours before symptom expression. This is all the more difficult to curb the spread of the virus.

Over the course of the year, there are yet some good news. Severe coronavirus are now better treated. “We learned to better treat it with corticoids, anticoagulants, and oxygen therapy. This is the tripod preventing intensive care with mechanical ventilation. Since last year, mortality decreased in severe patients and is now set around 30%”, Crémieux explains.

Vaccinating people the most fragile to the virus also enables to make the mortality curves decrease. These vaccines show they actually are working against severe forms of the virus. A recent study conducted in Scotland shows that one month after being given the first dose of Pfizer or AstraZeneca vaccines, people vaccinated tend to get fewer risks of developing severe and clinical coronavirus.

It should also be hailed how fast scientists and laboratories managed to develop effective vaccines assessed safe by health agencies and authorities.

What we do not know

Despite all these breakthroughs, many grey zones are still casting a shadow on Covid-19. Where does the virus come from? It was first suspected it originated from pangolins, but the animal is no longer suspected. After carrying out an investigation, WHO wrote a report raising more questions than it brings answers.

International experts entrusted with the file give four likely theories, including leak from a laboratory, and non-identified animal to human transmission. “Despite the investigations carried out by the Chinese authorities, today, no scientific evidence enables to draw conclusion among the different hypotheses proposed to explain where Sars-CoV-2 originates from” virologist Etienne Decroly regrets.

Yet, it is important to understand how this epidemic started if we want to prevent this event to occur again. “If the mechanisms underlying the outbreak of the Sars-CoV-2 epidemic are not identified, we take the risk of experiencing similar epidemiologic situations in the coming years”, the virologist told our peers from France Info.

Another answerless question: the uneven spread of the virus in the world and some places. “We have been struck over the course of the pandemic by the heterogeneity of the spread depending on territories”, Crémieux notices. “We can try and assess this heterogeneity, but it will be hard to predict. Do climate factors have a part to play? We do not know, neither why some areas are more exposed than others”.

Scientists are also wondering about the real number of people contaminated by Covid-19 since the pandemic broke out. Between cases not reported and asymptomatic people, the proportion of people who have been infected already is undoubtedly bigger than what is currently reported.

How long immunity lasts in people cured or vaccinated is also a preoccupying topic. It seems to vary from one person to another. This unknown quantity is yet a key to fight the epidemic and see life get back to normal. Unfortunately, for now, no clear pattern seems to stand out.

Crémieux also wonders about the future: “We know the vaccine will enable to decrease the spread of the virus. But are we heading to a low spread or zero Covid including the virus fully disappearing?

Schwartz adds: “Any epidemic aims at trailing off, but we don’t know when. When certain immunity will have been reached with vaccine, will there be waves, wavelets? We don’t know”.

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