A study from the University of Nebraska (United States) tends to prove that the Covid-19 is transmitted by aerosols. What do we really know ? What are the other means of transmission of the new coronavirus ?

Summary The droplets in The air, objects, food and water sexually, Intra-uterine The duration of infectiousness Avoid the contagion

For sure, the new coronavirus is transmitted through droplets and fomites. And it is likely that even minute particles can play a role in the spread of the disease. A team from the University of Nebraska (Usa) has managed to do is to replicate the particles of SARS-CoV-2 taken from the air. The first tends to prove that the Covid-19 is transmitted by aerosols. The report of the study was pre-published — without having to replay not a scientific committee — on the site medrxiv.org on Monday 20 July 2020. To arrive at these results, the researchers sampled the air in the rooms of five patients Covid-19, bed-ridden, 30 cm above their feet about. The research team has collected droplets less than five microns (1 micron is equivalent to 0.001 mm) in diameter containing the virus. Scientists have isolated the SARS-CoV-2, and have placed it in a special environment to make it replicate. On the 18 samples collected, three were able to be replicated with certainty. Joshua Santarpia, a professor at the medical centre of the university of Nebraska, explained to the AFP that the virus "replicates in cell culture and is therefore infectious." Professor Lindsey Marr, a specialist in aerial transmission of the virus, said on Twitter that the study showed "strong evidence" of airborne transmission. "There are the infectious virus in the air. Remains to know how much it is necessary to breathe in order to be infected", she added.

The transmission by droplets

according To the information available on the website of the government, the Covid-19 "can be transmitted by droplets (secretions projected invisible when talking, sneezing or coughing." A close contact with a patient is necessary to transmit the disease, it is referred to as "the same place of life, a direct contact to less than a metre during a discussion, a cough, a sneeze, or the absence of protective measures."

The transmission through the air

The study above, prépubliée by the University of Nebraska, tends to prove the airborne transmission of the Covid-19. Recently the world Health Organization (WHO) has recognized that evidence emerged on the transmission by the air in the coronavirus. "We recognise that evidence is emerging in this area and therefore we must be open to this possibility and understand its implications," said Benedetta Allegranzi, a person in charge WHO, during a virtual press conference on Tuesday 7 July. "The possibility of transmission by air in public places, particularly crowded, can not be excluded. The evidence, however, must be collected and interpreted", she continued, recommending the observance of the distanciations and effective ventilation in closed places. "When this is not possible, we recommend the wearing of the mask", she added. These statements are in response to the alert launched in the journal Clinical Infectious Diseases Oxford 239 scientists.

The transmission by the objects

In the New England Journal of medicine, researchers demonstrated that the Covid-19 last for four hours on the copper and metal, 24 hours on a piece of cardboard, three days on plastic, four days on wood and steel, five days on glass. De facto, the handles of doors, work plans, and other books may show traces of the virus. "These surfaces, these are the 'fomites' : all objects that potentially carry germs and that can cause problems in terms of hygiene in the management of the coronavirus," explained recently to 20Minutes Jocelyn Raude, lecturer-researcher in social psychology of health and infectious diseases at the Ecole des hautes études en santé publique (EHESP).

However, these conclusions are qualified. On the one hand, the majority of these studies are based on the projection of droplets of water highly charged virus SARS-CoV-2, on different surfaces with the help of an aerosol. In fact, the viral load is much lower outside experience in the laboratory. According to an article published in the Journal of Hospital Infection, "below 10 000 particles, the virus is resistant is less than 5 minutes, regardless of the surface." are on the other hand, the survival of the virus does not necessarily lead to a contamination. The viral load of the virus "are significantly reduced, up to 1000 times" , has explained on Twitter Angela Rasmussen, a doctor of virology at the University of Columbia in New York.

The transmission through food and water

According to the ANSES (national Agency of sanitary safety of food, environment and labour), " contamination of an animal being unlikely, the possibility of direct transmission of virus from a food from an animal infected has been ruled out by experts. "In contrast, "an infected person can contaminate food by preparing or manipulating it. "Also, the agency advises to cook the food, as a minimum, for four minutes at 63°C.

Regarding contamination of the water, the Centre of information on water has certified that "the different stages of treatment to protect the water of viruses, including the coronavirus." Several disinfection methods ", such as chlorination, ozonation, or uv disinfection can eliminate all viruses, including the coronavirus." It is stated that the "risk Covid-19 in itself does not justify surchlorer." A Spanish study has also reassured the most worried about. The CISC (Consejo Superior de Investigaciones Científicas), main council of research in the country, has ruled out the possibility that the virus develops in the sea water, but also in that of the swimming pool thanks to the presence of disinfectants such as chlorine. The study draws despite all the attention on the fact that swimming in fresh water natural lakes or rivers turns out to be more at risk.

sexual transmission

doubts have been raised about a possible sexual transmission and, more specifically, by the sperm. A study of the chinese, published in early may in the Journal of the American Medical Association, evokes this possibility. The experiment was carried out on 38 subjects Covid+. In 16% of patients the semen proved positive to the virus. The research team has admitted that "if it could be shown that the SARS-CoV-2 can be sexually transmitted, it could be an essential element in the prevention of the virus." The researchers have found that "abstinence or condom use can be preventative measures" for the positive patients. The authors recommended the conduct of additional clinical studies.

intrauterine transmission

A French study, published in the scientific journal Nature Communications, has confirmed the contamination of intra-uterine to the Covid-19. To do this, the research team analyzed the case of a baby, of the male sex, born in France in march and suffering from neurological symptoms associated with the disease. "We have shown that the transmission from the mother to the fetus via the placenta in the last weeks of pregnancy", explained to AFP the doctor, Daniele De Luca, of the hôpital Antoine-Béclère in Clamart (Hauts-de-Seine, france), lead author of the study. After a battery of tests, it turned out that the viral load is the most important has been found in the placenta. "It went from there, through the umbilical cord, to the baby, where it is developed", has developed the doctor Of Luca. The expert recalled : "The main message for pregnant women remains to avoid infection, hand washing, and social distancing."

The duration of contagiousness of the virus

A modeling study in China — published on Wednesday 15 April 2020 in the journal Nature Medicine — has found that the infectivity begins 2-3 days before the first symptoms of the Covid-19. The peak of contagiousness is 0.7 day before the first manifestations of the virus. In addition, 44% of secondary cases are infected during the period of pre-symptomatic.

The Pr Antoine Flahault, University of Geneva, has assured, that the more the foundations are severe the longer the patient is contagious. In fact, individuals who have few or no events are contagious for up to 14 days, those with moderate symptoms for three weeks and for the most severely afflicted 25 days.

1) on the form: the process is unpleasant : I sign my tweets, you not;
2) on the bottom : jendosse fully this infographic which summarises very didactic information currently available on the range of clinical forms, their freq., infectiousness, mortality pic.twitter.com/UjDG6NEgsE

— Antoine FLAHAULT (@FLAHAULT) April 8, 2020

How do you prevent contamination ?

to alleviate the possible contagion, we should observe the gestures, barriers, and rules of hygiene in the traditional way. On the side of the French Government, are also advised to disinfect the surfaces. "In addition to the regular cleaning, surfaces that are frequently touched with hands should be cleaned and disinfected twice a day, especially when they are visibly soiled. It is, for example, doorknobs, lift buttons, light switches, handles, toilets, counters, handrails, surfaces, touch screen and keyboard", is it specified on the site dedicated to the coronavirus. The digital objects and, in particular, smartphones are particularly targeted. Apple has already advised to clean it with disinfectant or wipes 70% isopropyl alcohol.

Date Of Update: 22 July 2020, 14:57