Quebecers expected a pandemic lull during the summer. Sunbathing away from COVID-19 and its multiple variants. They were rather caught, at the start of their holidays, by a seventh wave fed by BA.5 and BA.4. The duty takes stock of these new subvariants with four experts
Why do BA.5 and BA.4 spread so quickly although it is summer?
SARS-CoV-2 does not experience “seasonality” like respiratory viruses that are transmitted “mainly during winter” (such as respiratory syncytial virus or influenza virus, for example), indicates the Dr Donald Vinh, microbiologist-infectiologist at the McGill University Health Center. “It was assumed that COVID-19 would be transmitted little during the summer because it was a “respiratory” virus, he says. His behavior was misjudged. »
Since the start of the pandemic, Brazil, South America, Texas and Florida have been hit by major waves of COVID-19, and this “in the heat”, recalls Nathalie Grandvaux, director of the Laboratory. on the host response to viral infections at the Center hospitalier de l’Université de Montréal (CHUM).
The current high transmission is due to various factors. BA.5 and BA.4 are more transmissible than the other subvariants; they would even be almost as contagious as measles. “Before, we said that it took at least 15 minutes in a poorly ventilated place with an infected person to be contaminated, says Nathalie Grandvaux. Today, if we talk to someone who is contagious in a poorly ventilated place for a few minutes, we have every chance of being contaminated. »
Sanitary measures such as the obligation to wear a mask in shops and public transport were also lifted before the summer. “There are no longer any barriers in society,” says Dr.r Karl Weiss, president of the Association of microbiologists-infectiologists of Quebec. Global air traffic is almost back to a pre-pandemic state. The number of cases is increasing simply because the contacts are intense. »
BA.5 and BA.4 also manage to evade immunity conferred by another infection or the COVID-19 vaccine. These new sub-variants have undergone mutations and antibodies developed in the past are less effective in countering them.
Do we remain contagious longer with BA.5 and BA.4?
“With Omicron, we had hoped that after five days, the contagiousness would be over, which is really not the case, answers DD Caroline Quach-Thanh, microbiologist-infectiologist at the Sainte-Justine University Hospital Center (CHU). We remain contagious for 10 days as before. The situation does not change with BA.5 and BA.4.
According to the D.r Vinh, however, these sub-variants might require an isolation period longer than 10 days. “It may be that the elimination of the virus is a little bit slower, because of the high viral load of BA.5,” he says.
The Dr Weiss believes, on the contrary, that a “paradigm shift” is needed with regard to the isolation of infected people. Currently, Public Health recommends that the population completely isolate themselves for five days, then wear a mask “during all social interaction” for the following five days. Non-essential “public” activities, such as dining out, visiting friends or attending festivals, should therefore be avoided.
“We have triple-vaccinated health care workers who test positive, who are hardly sick and who are put away from the hospital system for 10 days, deplores the Dr Weiss. We cancel operations, we cancel activities. » The Dr Weiss reminds workers not to stay home for 10 days when they have the flu. “We will have to review the way we perceive, from a societal point of view, COVID and how we live with it. It is clear that we will not get rid of the virus anytime soon. »
Is the disease less serious when infected with BA.5 and BA.4?
It is difficult to answer this question with the data collected in Quebec. Since PCR tests are reserved for certain categories of the population (healthcare workers and the elderly, in particular), it is difficult to truly quantify the number of people infected. Impossible, therefore, to know the exact proportion of individuals ending up in the hospital because of these new sub-variants.
“Despite the number of people who are currently infected, the number of hospitalizations is increasing, but not at the same speed as the number of cases, observes the DD Quach-Thanh. So, it feels like in terms of severity, it’s not on par with the 2020 ancestral strain.”
The Dr Vinh says it’s “not clear if BA.5 causes more severe disease.” “The severity of the disease does not depend exclusively on the virus, but on the immunity acquired by the population and by the individual [touché] “, he explains.
A “large part of the population has been vaccinated and has already [eu] COVID-19,” recalls the Dr Weiss. “Of the total number of people infected, the severe disease that will lead to direct hospitalization directly related to COVID, death or major complications, is a relatively very rare phenomenon, even if it unfortunately exists”, affirms the physician who practices at the Jewish General Hospital in Montreal.
To better detect variants and assess their dangerousness, Dr Vinh believes that Quebec must acquire better infrastructures. “If we look at the online data of the[Institut national de santé publique du Québec] on the variants, it dates from June 19th! »
The Dr Vinh also invites Public Health and the Legault government not to see the possible reinstatement of health measures “as a failure”, he said. He cites as an example a patient who no longer has hypertension thanks to a drug. “We can stop the medication, if we see that the pressure remains normal. But if we see it coming back up, we’re going to recommend the drug. It is the same for public health measures. »