Risks of contagion, plasma, infected animals: the latest work on the coronavirus

Can Covid-19 be transmitted simply by breathing? This is the question that has stirred the scientific community since studies have pointed to the presence of the new coronavirus in the microscopic particles that we emit by speaking or breathing.

Until then, the health authorities considered that the transmission of Covid-19 in the air took place when a sick subject coughed or sneezed, in the form of projections of droplets containing the virus. More simply, it was especially necessary to escape the postillons of his interlocutor to avoid being contaminated.

According to the journal Science, the latest work from the American Academy of Sciences evokes a far more pernicious threat: aerosols. Scientists use this common term to designate clouds of particles a thousand times smaller than postilions - and therefore totally invisible to the naked eye - that everyone emits simply by breathing. Problem: these aerosols stay longer in the air and can travel further, up to seven to eight meters away, according to the American scientist Lydia Bourouiba, associate professor at the American Research Institute MIT.

This work does not provide definitive proof that the aerosols have contaminated patients. It remains in particular for researchers to determine if the quantity of virus present in these microscopic particles is sufficient to infect a third person. Questioned by LCI, Professor Yves Buisson, member of the National Academy of Medicine, believes that these aerosols could have a contaminating role only in very confined spaces "such as elevator shafts, shops, public transport… ". According to him, there is little risk of being infected on the street. This work could nevertheless encourage health authorities to reinforce recent calls for the wearing of a generalized mask.

>> To read on France 24: Generalized wearing of masks: "We must do everything to avoid a second wave" by Covid-19

Felines likely to catch Covid-19

Nadia is not a head of state or a sports celebrity, but the announcement of her coronavirus infection on Sunday, April 5, went around the world in a flash. This 4 year old Malaysian tiger is indeed the first wild animal to have been infected by a human being. In any case, this is what the New York Bronx Zoo suspects after the return of a positive coronavirus test. Six other cats have coughs and lack of appetite. In addition to Nadia's sister, two Siberian tigers and three African lions have actually developed symptoms that correspond to the Covid-19 infection. However, the other felines - leopards, cougars, cheetahs, snow panthers - do not seem to have been contaminated.

🇺🇸 FLASH - Tiger infected with #coronavirus: this is a 4 year old #Malaysian tigress named Nadia which is infected with # Covid_19. 6 other tigers and lions have symptoms of #virus. The #Bronx zoo has been closed since March 16. (ABC7) #COVID #NewYorkCity pic.twitter.com/D8Fxf0HvUR

The issue of Covid-19 infection in pets has been studied by the Harbin Veterinary Research Institute in northeast China. Scientists had then introduced the new coronavirus into the noses of five cats to find that they could actually be infected. Three of these infected cats were then confined in a cage near other cages containing three cats not carrying the virus. One of these healthy subjects was contaminated by the coronavirus, reinforcing the hypothesis of the possibility of contamination from cat to cat.

Other animals have undergone the same coronavirus inoculation treatment. Chickens, pigs, and ducks have not contracted the disease. Two out of five dogs have developed a limited, non-contagious viral load. The study, which has not yet been evaluated by other researchers, therefore states that the risk of pets becoming a reservoir for Covid-19 is very limited.

A conclusion which joins the announcement of the Belgian health authorities after the positive test of a cat with the coronavirus at the end of March. The latter then emphasized that the animal had been contaminated by its sick master and excluded any risk of contamination from animal to man.

The plasma of convalescents to the rescue

While chloroquine treatment took center stage in France, Chinese studies have raised a glimmer of hope for treating Covid-19 patients using plasma - the liquid part of the blood - of cured patients . This would make it possible to prepare a therapeutic fluid which contains the precious antibodies, these organisms secreted to fight against a foreign substance, in this case the new coronavirus. On paper, the idea therefore consists in transfusing the plasma of cured patients towards a sick person in order to stimulate their immune defenses and to get rid of the virus.

The study carried out by a research center in Wuhan, which has not yet been evaluated by other researchers, consisted precisely in transfusing plasma from convalescents to ten patients, who were seriously ill with Covid-19. Six days after the injection, the virus had disappeared from the body of seven out of ten patients. A second study done in Shenzhen and pre-published March 27 in the journal of the American medical association also showed promising results, but on an even smaller sample of five patients.

This did not prevent the Methodist Hospital of Houston and the Mount Sinai Clinic in New York from launching, on March 28, their own program to test this so-called "therapeutic plasma" option.

"It is a gamble in terms of time, energy, and money," an American infectious disease specialist, William Schaffner, told the newspaper USA Today, stressing that this method had yielded fluctuating results in the past, according to diseases. But circumstances dictate, he says, to launch these programs as quickly as possible.

France got into gear with the announcement of the start on April 7 of a clinical trial called Coviplasm for 60 patients in Parisian hospitals. A joint statement from the Assistance Publique-Hôpitaux de Paris (AP-HP), the French Blood Establishment (EFS) and the National Institute of Health and Medical Research (Inserm) said that targeted samples would begin as of Tuesday in Île-de-France, in Grand Est and in Bourgogne-Franche-Comté, with around 200 patients cured for at least fourteen days. The first evaluation of this French study is expected within two to three weeks.

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