Health and if we finally understand the Covid transmission?

and if we finally understand the Covid transmission?

Several cases of Covid-19 have been identified in slaughterhouses. Why are these sites frequently affected by the epidemic? What are the modes of transmission of the new coronavirus?

[Mis à jour le 22 mai 2020 à 12h45] Numerous “clusters” have been identified in slaughterhouses and meat processing plants. In France, the Kermené slaughterhouse in the Côtes-d’Armor was hit hard. Of the 1,027 employees tested, 109 were infected with Covid-19. The first such “cluster” was detected in Germany, in a slaughterhouse in Birkenfeld. 300 employees, including 200 Romanian, had been contaminated. To explain this multiplicity of cases, the living conditions of workers (dilapidated collective habitats and public transport) were mentioned. However, part of the scientific community agrees that the problem is not only material. Christian Drosten, head of the institute of virology at the Charity hospital in Berlin, said in a podcast broadcast on NDR: “You have to wonder if these precarious living conditions explain everything, or if there is also not another factor. ” According to Gilles Salvat, deputy director general of the National Health Security Agency, this other factor would be the temperature. “In a cutting workshop, the average is 4 to 8 ° C. These are very cold and humid atmospheres, favorable for the survival of the virus. In these workshops, the proximity of people can be very important, and with humidity , the masks lose their filtration capacity and rarely last 4 hours, “he explained in Le Monde. A scientific article, published by the American Centers for Disease Control and Prevention (CDC), focused on working conditions. The researchers mentioned the “difficulty of maintaining a distance of at least 2 meters between two employees on the production lines” and “the pace and the physical demands of the work” which prevent the wearing of an optimal mask. In addition, the American organization underlined “socio-economic difficulties which could involve the arrival at work of sick people”.

Many other questions arise about the transmission of the coronavirus, in particular via everyday objects. Researchers in the New England Journal of Medicine have shown that Covid-19 lasts four hours on copper and metal, 24 hours on cardboard, three days on plastic, four days on wood and steel, five days on glass. De facto, doorknobs, worktops and other books may show traces of the virus. “These surfaces are the ‘fomites’: all objects potentially carrying germs and which can pose hygiene problems in the management of the coronavirus”, Jocelyn Raude, professor-researcher in social psychology of health and infectious diseases at the Graduate School of Public Health (EHESP).

A previous study, published in the American scientific journal JAMA, and carried out by researchers from the National Center for Infectious Diseases of Singapore and the DSO National Laboratories, is also abundantly cited. Carried out on patients confined to their rooms, it showed that they had, depending on the symptoms, lightly or severely soiled the rooms and furniture. In the rooms 13 of the 15 surfaces analyzed were contaminated, including the chair, the bed, the window and the floor, even with a patient presenting a simple cough. In the bathroom, sinks and bowls were severely affected by “traces of the virus”.

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

In practice, your food purchased commercially can be contaminated. However, contrary to certain information which could circulate on Internet, to leave its races 1:30 in the trunk of its car would not be used for nothing. “We don’t know where this 1.5 hour duration comes from because if we look at the latest studies on the survival capacity of the virus on surfaces, researchers are talking about durations ranging from 1 to 3 days. ‘It is not conceivable to leave your shopping in quarantine for such a long period “, said Bruno Grandbastien, medical officer of health, on LCI, who evokes” other precautions “,” like throwing away the cardboard or plastic packaging, cleaning the fresh products before consumption and wash your hands when everything is unpacked. “

ANSES (National Agency for Food, Environmental and Occupational Health Safety) has studied the potential transmission of the virus through food. “Since contamination of an animal is unlikely, the possibility of direct transmission of the virus through food from an infected animal has been ruled out by experts,” the study concluded. On the other hand, “an infected person can contaminate food by preparing or handling it. Also, the agency advises to cook the food, at least, for four minutes at 63 ° C.

Some concerns about Covid-19 contamination by water may have arisen, in particular following a press release from the City of Paris indicating that a “tiny amount of traces of the virus” has been detected in its non-water network. potable (watering, street cleaning, etc.). But if the city hall of the capital was reassuring, a Spanish study also reassured the most worried about this. The CISC (Consejo Superior de Investigaciones Científicas), the country’s main research council, has ruled out the possibility that the virus develops in seawater, but also in swimming pools, thanks to the presence of disinfectants such as chlorine. The study nevertheless draws attention to the fact that swimming in natural fresh waters such as lakes or rivers is more at risk.

Recently, doubts have been expressed about a possible transmission by sexual means and more specifically by sperm. A Chinese study, published in early May in the Journal of American Medical Association, suggests this possibility. The experiment was carried out on 38 Covid + subjects. In 16% of patients the sperm tested positive for the virus. The research team admitted that “if it can be proven that SARS-CoV-2 can be sexually transmitted, it could be essential in preventing the virus.” The researchers felt that “abstinence or using a condom can be a preventive measure” for positive patients. The authors recommended further clinical studies.

A study on the question, which was the subject of many questions, was made public on Tuesday, May 13 on the antenna of BFM TV by Robert Cohen, pediatrician and infectiologist at the hospital of Créteil (Val-de- Marl). According to the latter, who was part of the team of pediatricians who conducted the study, the risk of the disease in children is “extremely low, we can say a thousand times lower than in adults”. “Children are weak carriers, poor transmitters, and when they are infected it is almost always adults in the family who have contaminated them,” he also explained. Reassuring remarks therefore, especially if we add that even between them, children are very little contagious, according to Robert Cohen, who rules out the revival of the virus caused by the reopening of schools. “Children outside the school are probably more at risk than inside the school,” he said.

Since the beginning of the epidemic, the Government has advocated maintaining a social distance of one meter. However, according to a study carried out in the Chinese province of Wuhan, the cradle of the pandemic, and published on Friday April 11, 2020 by the American Centers for Prevention and Control of Patients (CDC), the virus could travel up to four meters from a sick. The Chinese researchers who carried out the study worked on 15 patients affected by Covid-19 from a resuscitation unit at the Huoshenshan Field Hospital in Wuhan and 24 others less seriously affected in a general care unit of the prefabricated hospital that has toured the media around the world. Between February 19 and March 2, they took samples from patient masks, beds, floors, caregivers’ protective equipment, including computer equipment, garbage cans, air vents. they also carried out several capture of the ambient air in the rooms.

The research team concluded that “SARS-CoV-2 (covid-19) was widely distributed in the air and on the surface of objects in intensive care and general care, which poses a potentially risk high contamination for health care workers and other close contacts. ” The researchers identified that “the maximum transmission distance for a SARS-CoV-2 aerosol could be four meters”.

How long is a patient contagious?

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

Pr Antoine Flahault, University of Geneva, assured that the more severe the prodromes the more the patient is contagious. In fact, individuals who present little or no manifestations are contagious for 14 days, those with moderate symptoms for three weeks and for the most severely affected 25 days.

Recently, French researchers admitted – in the Oxford University Press – that the “dynamics of transmission [du coronavirus est] potentially different in children. “However, according to a German study, led by Professor Christian Drosten,” children can be as contagious as adults. “The research team examined the samples of 3,712 patients. then analyzed “the relationship between patient age and SARS-CoV-2 viral load.” They found that these “data indicate that viral loads in very young people do not differ significantly from those in adults.” the report noted: “It is evident that children are underrepresented in clinical studies and less frequently diagnosed due to mild or absent symptoms.”

In order to mitigate possible contagions, it is necessary to respect barrier gestures and traditional hygiene rules. On the side of the French Government, we also advise to disinfect surfaces. “In addition to regular cleaning, surfaces that are frequently touched with the hands should be cleaned and disinfected twice a day, especially when they are visibly soiled. These include door handles, elevator knobs , light switches, toilet handles, counters, handrails, touchscreen surfaces and keyboards, “said the site dedicated to coronavirus. Digital objects and in particular smartphones are particularly targeted. Apple has already advised to clean them with disinfectants or wipes with 70% isopropyl alcohol.

The World Health Organization (WHO) also says that “if you think a surface may be infected, clean it with ordinary disinfectant to kill the virus”. The recommended solvent dosage is four teaspoons for one liter of water. It is advisable to wash soiled sheets and clothing at 60 ° C. In a page devoted to the fight against misconceptions about Covid-19, the WHO also indicates that “disinfectants based on bleach or chlorine, solvents, 75% ethanol, peracetic acid and chloroform “are effective against the virus.

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