tration said “the period between the contamination and the first symptoms appear,” is 3 to 5 days in general. “It may, however, extend up to 14 days”, writes the ministry of Health. And it is during this period of 3 to 14 days, a patient can be contagious. This is the reason why a quatorzaine has been adopted across the world, in various cases : in prevention in some countries for every entry on the territory, in the face of a suspicion of a Covid, or, in most cases, after the detection of the disease, following a positive test. In France, this quatorzaine has been reduced to a “septaine” (7 days), the September 11, 2020, after the favourable opinion of the scientific Council. “It is more contagious in the first five days of symptoms or a positive test. Then, the contagiousness decreases in a very important way, and beyond a week, it remains, but is very weak,” explained the minister of Health Olivier Véran. According to him, “beyond 10 days, it is less than 5% of the people is contagious, and weakly contagious”. This reduction in the septaine, however, has been discussion in the scientific world, some scholars deeming the risk too high. Exceptions have been identified in the reviewed scientific, as in the case of an elderly woman asymptomatic for a period of 70 days, but still contagious, which is mentioned in the journal Cell. A special case nevertheless.
What are the places at risk of contamination Covid-19 ?
The methods of transmission of the coronavirus continues to be examined by scientists and health authorities, through statistics, as well as by laboratory work. Each week, public Health France is the point in the epidemiological bulletins on the data of the clusters and can thus establish a list of the places with the most outbreaks of infection, mainly the long-term care facilities, public and private sector and health facilities (the “school and university” has also been a time a large number of clusters). A major study is currently underway in France on the places and modes of contamination.
An american study published in the prestigious scientific journal Nature on Tuesday 10 November 2020, has already operated millions of data to get a clearer view on the places at risk. Directed by Serina Chang, Stanford University, us scientists have mapped the travels of the 98 million people in the month of march to may 2020. Scientists have garnered 57 000 places of residence. The displacements recorded ranged up to 553 000 “points of interest”, with shops, boutiques, places of worship or places of hospitality and catering industry. To measure the dynamics of the Covid-19 in public places, the researchers used an epidemiological model behavioral called SEIR (Susceptible-Exposed-Infectious-Removed).
The results of this study are not a surprise. They suggest that the restaurants, gyms, cafes, hotels and religious establishments are places where the virus is circulating most actively. The majority of these places, ranked by decreasing order of contamination, does not require wearing a mask constantly. It is also closed places, sometimes in poorly ventilated areas, or activities (sport, song, food, conversation) prevent the wearing of the mask and/or encourage the projection of droplets through the mouth. This study, although rewarding, however, has limits. The mobile data were not available in the schools or the retirement homes, facilities very crowded in the day. The companies have not been counted.
The Spanish daily El Pais has also explained in the fall of 2020 that places silent were less conducive to the spread of the disease. If a sick person is silent, the aerosols are not very numerous. When the latter begins to speak, it makes ten times more particulate matter than remaining silent.
The Covid-19 can be transmitted through the air ?
the page devoted to The Covid-19 on the website of the ministry of Health is adamant : “No”, the coronavirus “can’t live on air alone”. “The virus is carried by the droplets, it does not circulate in the air all alone, but can reach a person in close proximity (<1 meter) or set on a surface contaminated by droplets, such as hands or handkerchiefs," can one still read, in November 2020, on this official source. The world Health Organization, it is more nuanced. It states on its website that "the virus can spread when small liquid particles are expelled through the mouth or through the nose when an infected person coughs, sneezes, speaks, sings, or breathes deeply". And added : "these liquid particles are of different sizes, ranging from large 'respiratory droplets' of 'aerosols' little people'.
following an alert launched at the beginning of the month of July 2020 in the journal Clinical Infectious Diseases Oxford 239 scientists, the 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, July 7, 2020. “The possibility of a sent
