The Covid virus is still very contagious. The initial Sars-CoV-2 contaminated 3 people, the Omicron variant nearly 10 and the sub-lineages circulating in 2024 even more.
Appeared in China in December 2019, the Covid-19 disease had contaminated more than a million people worldwide at the beginning of April 2020, proof of the high contagiousness of its virus, the SARS-CoV-2. There transmission capacity of this coronavirus is evaluated through the measurement of “R0”. This “R” corresponds to 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 The French health authorities have no longer updated the evolution of the “R” since June 2023 since the virus is circulating less than in previous years. In December 2024, it is the JN1 variant descending from Omicron which remains in the majority (since November 2023) in France and internationally. This variant is associated with “A greater immune escape“ and to “a growth advantage” compared to the sub-lineages which circulated until now but “in terms of severityno concerning signals have been associated with JN.1” reassures Public Health France. Among the JN.1 sub-lineages, the KP.3.1.1 lineage dominates in France. The KP3 could “better escape the immune system. The decline in immunity and low uptake of the latest COVID-19 vaccine (in the United States, editor’s note) have created a more susceptible population. underlines the American site Today.com.
What is the definition of the term “contagion”?
The word “contagion” comes from Latin “cum” which means “with” and “tanger” for “touch”. In medical language, contagion is defined by the transmission of an infectious agent and, where applicable, the corresponding disease, from a contaminated subject to a healthy individual, by direct contact (skin, mucous membrane) or indirect (airborne transmission (saliva , spittle…), digestive…).
The Sars-CoV-2 virus spreads mainly in case of close contact with an infected person, by small liquid particles expelled through the mouth or nose if the contaminated person coughs, sneezes, speaks or breathes deeply. “You can also contract Covid-19 when the virus enters the mouth, nose or eyes, a situation more likely when people are in direct or close contact (less than a meter away) with an infected person” indicates the WHO. You can also be contaminated if you touch your eyes, nose or mouth before washing your hands, after touching a contaminated surface. Transmission of the virus is increased in indoor, crowded and insufficiently ventilated spaces.
How long are you contagious when you have Covid?
When the Covid virus appeared at the end of 2019-beginning of 2020, the duration of contagion extended from 2 days before the onset of symptoms to continuing for up to 8 days on average. With the majority Omicron variant since the end of 2021, “replication is faster everything shortens, including the symptomatic – or asymptomatic phase but contagious explained Professor Alain Fisher, head of the former Vaccination Strategy Council for France, to Les Echos. According to a Japanese study, the amount of viral RNA (or “viral load“) Covid-positive patients are especially elevated 3 to 6 days after diagnosis or after the appearance of their symptoms and then gradually diminish.
“We do not excrete the same quantities of virus if we have a virus that infects the nose or the throat”
We would therefore be contagious for about a week but this duration of contagiousness varies depending on the individual, recalled the president of Covars Brigitte Autran in 2023 on France Inter: “There viral load varies enormously depending on severity of illness and symptomatology. We do not excrete the same quantities of virus if we have a virus that infects the nose or the throat. There is of course a proportionality between the number of viral particles produced and the number of contaminations that we risk doing.”
How contagious is the Omicron variant?
The majority Omicron variant since 2021 is the most transmissible Covid variants. His predecessors, theAlpha came from England then Delta who came from India, were less contagious. According to a study relayed by the University of Geneva in 2023, on average, a person infects a little more than three out of ten of their contacts, mainly within the family unit, and up to four out of ten with Omicron. According to studies reported by Public Health France, “Omicron is approximately 3 times more transmissible than Delta”. “A professor of medicine in the United Kingdom says that, without barrier measures, the R0, the reproduction rate would be close to 10” informed epidemiologist Éric d’Ortenzio from Inserm on TV5Monde on December 31.
What is the incubation period for Covid?
Incubation covers the period between contamination by the virus and the appearance of the first symptoms. The median incubation period for Covid-19 is initially 5 days but has been reduced to 3 days with Omicron. We can therefore allow approximately 3 days between the moment when we are in contact with the virus and the moment when the first symptoms appear if we are contaminated. During this periodthe person may be contagious. A meta-analysis published in 2022 in the JAMA Network by Chinese researchers based on 142 publications (8,112 Covid patients) confirmed the reduction in the incubation period of the virus with Omicron. Precisely :
- 3.4 days with the Omicron variant.
- 4.4 days with the Delta variant
- 5 days of incubation with the Alpha variant
Viral load peaks during the first week of illness.
How long are you contagious before Covid symptoms start?
A person positive for Covid-19 is considered contagious from 48 hours before the appearance of symptoms.
How long are we contagious after the start of Covid symptoms?
According to Japanese analyzes from January 2022 on Omicron cases, the viral load of the virus would be maximum 3 to 6 days after diagnosis or start of symptoms then would decrease. There contagion is therefore particularly strong in the first week following the onset of symptoms. The WHO also informs that “people who develop severe form of the disease can be contagious for longer. Likewise, those who have more symptoms appear to be more contagious than asymptomatic cases. “We do not excrete the same quantities of virus if we have a virus that infects the nose or the throat. a proportionality between the number of viral particles produced and the number of contaminations what we risk doing” explained Brigitte Autran on October 10, 2023 on France Inter.
Are we contagious when we do not have Covid symptoms (asymptomatic)?
A person positive for the Sars-CoV-2 virus, who has no symptoms, is contagious and can infect other people. However “transmission of Covid-19 occurs mainly from people with symptoms” indicates the WHO. The longer and closer the contact, the more the risk of contamination increases (more than 15 minutes, less than two meters). If in doubt, wearing a mask is still recommended.
