Covid contagion: incubation time, before symptoms?

Covid contagion: incubation time, before symptoms?

Even in the summer of 2022, Covid-19 remains a highly contagious disease. The initial Sars-CoV-2 virus infected 3 people, the Delta variant more than 6, the Omicron variant nearly 10, and its BA5 subvariant is even more contagious. Period of contagion, before and after symptoms, asymptomatic…

Appeared in China in December 2019, the Covid-19 disease had infected more than a million people worldwide by early April 2020, proof of the high contagiousness of his virus, the SARS-CoV-2. the transmission capacity of the coronavirus Sars-CoV-2 is evaluated through the measurement of “R0”. This “R” corresponds to the reproduction rate of the virus and indicates the number of people infected by a positive case of Covid-19. The higher it is, the more the disease is transmitted. the release of variantsFirst theAlpha came from England then the Delta came from India and the omicron from South Africa changed the game because they were much more contagious than the original 2020 Sars-Cov-2 strain. subvariant BA.5 by Omicron majority in France since mid-June is more contagious than BA.2, itself already more transmissible than Omicron’s BA1 sublineage what “It shows the evolutionary capacity of the virus capable of evading vaccines, while increasing its transmission” explained infectious disease specialist Anne-Claude Crémieux on FranceInfo on June 22. At the end of July, the 7th wave descends with a reproduction rate of the virus that falls below the threshold of 1 (a contaminated person infects less than another). Public Health France also reports a increase in the proportion of Covid reinfections from December 2021. how many days are you contagious when are you positive for covid? 5 days ? 10 days is the isolation time? We are contagious if no symptoms ? During the incubation period? Focus on knowledge.

Effective reproduction rate of the Covid virus in France as of July 23, 2022 © Government.fr

What is the definition of the term “contagion”?

The word “contagion” comes from the Latin “semen” which means “with” and “tange” touch”. In medical language, contagion is defined as the transmission of an infectious agent and, where appropriate, of the corresponding disease, from an infected subject to a healthy individual, by direct contact (skin, mucous membranes) or indirect (transmission aerial (saliva, postilions)…), digestive…).

The Sars-CoV-2 virus is spread mainly by case of close contact with an infected personby small liquid particles expelled through the mouth Where through the nose if the infected person coughs, sneezes, talks or take a deep breath. “You can also get Covid-19 when the virus enters through the mouth, nose, or eyesa more likely situation when people are in direct or close contact (less than a meter away) with an infected person” says the WHO. It can also become contaminated we touch our eyes, nose or mouth before washing hands, after touching a contaminated surface. the virus transmission increases indoorsovercrowded and insufficiently ventilated.

Duration: what is the contagion time of Covid?

The contagious phase of a Covid-19 positive patient is initially 8 days on average and start over 2 days before symptoms start. With the Omicron variant, “replication is fasterconfirmed Professor Alain Fisher at the head of the French Vaccine Strategy Council, to Les Echos. Then, everything is shortened, including the symptomatic or asymptomatic phase but contagious.

According to study by Japanese researchers published in January 2022, is cases vaccinated with Omicron are unlikely to clear infectious virus 10 days after diagnosis or the appearance of its symptoms (as was the case with the original virus, editor’s note). The amount of viral RNA (or “viral load“) was higher 3 to 6 days after diagnosis (test) or 3 to 6 days after symptom onsetthen gradually decreased over time. we would be like this contagious for a shorter time (6 days instead of 10) and not necessarily before the onset of symptoms with the Omicron variant.

How contagious is the Omicron variant?

The Omicron variant became the majority in France at the end of 2021 in just a few weeks. The number of infections was doubling every 2-3 days in late November and early December, much faster than when the Delta spread. According to studies reported by french Public Health, “Omicron is about 3 times more transmissible than Delta”. “A professor of medicine in the United Kingdom claims that, without barrier measures, the R0, the reproduction rate it would be around 10“, reported the epidemiologist Éric d’Ortenzio of Inserm on TV5Monde, on December 31. His incubation period is also shorter: “Replication is faster, confirmed Professor Alain Fisher at the head of the French Vaccine Strategy Council, to Les Echos. Then, everything is shortened, including the symptomatic or asymptomatic phase but contagious. According to a Japanese study published in January 2022, the viral load is high 3-6 days after Omicron diagnosis (test) or the appearance of its symptoms. Omicron’s majority BA.2 subvariant in France until early June was “more contagious than its predecessor” (BA1), Professor Arnaud Fontanet had indicated in France Inter on March 14. around 30% the rest. and the subvariant BA5 now majority”spreads better than BA.2″ what “It shows the evolutionary capacity of the virus capable of evading vaccines, while increasing its transmission” explained infectious disease specialist Anne-Claude Crémieux on FranceInfo on June 22.

What is the incubation period for Covid?

Incubation covers the period between contamination by the virus and the appearance of the first symptoms. The average incubation period for Covid-19 is initially 5 days, but has been reduced with omicron. As Professor Yazdan Yazdanpanah of the Scientific Council explained on BFM-TV on January 2, 2022,we are facing a variant that has a duration (incubation, editor’s note), before the onset of symptoms, which was 5 to 3 days. So we can be in contact with the virus and have the first signs of contamination three days later. During this period, the person can be contagious.

Viral load peaks in the first week of illness.

How long are you contagious before the onset of Covid-19 symptoms?

“According to laboratory data, it is mainly just before infected people develop symptoms (i.e. two days before the onset of symptoms) and early in the illness they are the most contagious” has explained the World Health Organization at the beginning of the coronavirus epidemic in 2022. Today, before the variant omicronresearch has not shown that people are contagious before their diagnosis (test) or their symptoms, but rather during the first week. A British meta-analysis bringing together 79 studies on Sars-CoV-2 (5,340 people) published on November 19, 2020 in the scientific journal the lancet had already shown that viral load of the coronavirus Sars-CoV-2 in the upper respiratory tract reached its peak during first week of illness.

How long are you contagious after the start of Covid symptoms?

After the 5th day, the viral load decreases.

According to the British authors of the study Lancet published in November 2020, the the peak of contagion of a positive person of Covid-19 extends until 5me day after symptom onset. Subsequently, the viral load decreases. Based on January 2022 Japanese analysis of cases omicronthis viral load would be maximum 3 to 6 days after diagnosis or symptom onset then it would decrease. The authors also considered it to be Vaccinated Omicron cases are unlikely to clear infectious virus 10 days after diagnosis or the appearance of its symptoms”. Therefore, contagion is particularly strong in the first week after the onset of symptoms. The WHO also reports that “People who develop a severe form the disease can be contagious longer.

Are you contagious when you have no symptoms of Covid (asymptomatic)?

A person infected with the Sars-CoV-2 virus but not showing symptoms is contagious and can infect other people. Similarly, someone who never develops symptoms can also transmit the virus even though “It is not yet clear to what extent this is happening” says the WHO. Note that if asymptomatic cases are contagious, “The transmission of Covid-19 occurs mainly by people with symptoms” indicates the agency.

What is the risk of having Covid 2 times or more?

Public Health France reports on July 7 to increase in the proportion of Covid reinfections as of December 2021, rate of diffusion of the Omicron variant (12% of confirmed COVID-19 cases in week 23 (June 6-12, 2022) were possible cases of reinfection). A high number of reinfections with Omicron are observed after a first infection with this same variant. However, the probability of reinfection after a first infection with another variant (Alpha, Delta or other) is even greater. “The the likelihood of reinfection increases with age at first infection to get to a shelf about 6 months after the first infection.

A contact case is a person who has been in contact without protective measures (such as a type 1 mask) with a Covid-positive person. The longer and closer the contact, the greater the risk of contamination (more than 15 minutes, less than two meters)underlines the Ministry of Health. A contact person must be tested on D+2.

Sources:

The SARS-CoV-2 variant, Omicron, displays rapid replication in human primary nasal epithelial cultures and efficiently utilizes the endosomal pathway of entry. Thomas P. Peacock1. Department of Infectious Diseases, Imperial College London, UK, W2 1PG

Recommendations regarding the vaccination strategy. Senate press conference Thursday, July 1, 2021.

Covid-19 – Get vaccinated? Decide with your doctor. January 29, 2021. HA

Vaccination against Covid-19: transparency, pragmatism and flexibility are the keys to an effective campaign. Press release. November 9, 2020. HAS.

Rapid responses in the context of Covid-19 – Frontline care of suspected Covid-19 patients. Validated by the College on June 18, 2020. Updated on November 5, 2020. HAS.

How is COVID-19 transmitted? July 9, 2020. WHO.

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