Covid-19: is the BA.5 variant, which is progressing rapidly in France, more virulent?

The Omicron BA.5 subline is progressing rapidly week after week in France. Identified in early April, it seems to cause more symptoms in patients, but not more hospitalizations.

For several weeks now, the number of Covid-19 cases has been on the rise again, with an increase in the Omicron BA.5 variant, which is gradually replacing BA.2, hitherto dominant in France. This increase signals the arrival of a 7th wave in France, even if its health impact is not yet known.

“The question is: ‘how strong is the wave?'”, launched this Wednesday on France 2 Alain FischerChairman of the Vaccine Strategy Advisory Board.

The Omicron BA.5 sublineage was identified in early April 2022 in South Africa, along with the BA.4 sublineage. It has therefore only been observed and analyzed for two months, which still leaves a lot of room for guesswork about it, even if trends are emerging.

“Anosmia and ageusia, but also nausea, vomiting and diarrhoea”

In its latest risk analysis on variants, Santé Publique France (SPF) notes a stronger possibility of having symptomatic disease with these variants. “The probability of presenting anosmia and ageusia, but also nausea, vomiting and diarrhea was higher for the BA.4/BA.5 cases compared to those of BA.1”, writes the organization.

“BA.4/BA.5 cases also reported longer duration of clinical signs.”

Difference in age and symptoms between people infected with BA.1 and those infected with BA.4 or BA.5
Difference in age and symptoms between people infected with BA.1 and those contaminated with BA.4 or BA.5 © Santé Publique France

However, “the hospitalization rate was not significantly higher for BA.4 and BA.5 compared to BA.1 and the majority of hospitalized cases had risk factors”.

If the people affected statistically have more symptomatic Covid-19 than with the previous sub-variants of Omicron, they do not necessarily go to the hospital more, which is observed, for the moment, in the figures of the ‘epidemic.

“There are more cases every day, but for the moment this does not translate significantly into an increase in the number of hospitalizations, let alone the number of deaths. But we know that there is always a lag”, recalls Alain Fischer.

A preliminary study on hamsters published in May thus points to a potential greater severity of the BA.4 and BA.5 sub-variants, in particular because they seem to favor the infection of the lung cells rather than the tissues of the respiratory tract. “But these results should be taken with caution”, notes SPF, because “the hamster model is difficult to transpose to humans”.

“No signal in terms of severity has been reported”

“To date, little data is available on the characteristics of BA.2.12.1, BA.4 and BA.5”, underlines SPF, adding then that for the moment, “no signal in terms of severity has been reported for these three sub-lineages, and the investigations of the cases of BA.4 and BA.5 carried out by Public Health France go in this direction.

Observations from South Africa and Portugal, where the epidemic peak has passed, also tip some observers towards reasoned optimism about the increased risks of hospitalizations and deaths.

On the other hand, SPF notes that BA.4 and BA.5 are “genetically closer to BA.2 than to BA.1, and a previous infection with BA.2 could therefore confer better protection”. The sustained circulation of BA.2 in recent months in France could thus “have a protective effect against BA.5 and further moderate its impact.”

“Based on limited data, there is no evidence that BA.4 and BA.5 are associated with increased severity of infection compared to BA.1 and BA.2 variants,” writes the ECDC (European Center for Disease Prevention and Control) in a report dated June 13, 2022. “However, as in previous waves, an overall increase in Covid-19 cases may lead to increased hospitalizations, ICU admissions and deaths.”

“We have to take care of it”

For the moment, the real concern around the rise of BA.5 in France indeed concerns its high contagiousness. This variant “represented 24.2% of interpretable Flash sequences” the week of May 30 to June 5, “compared to 13.3%” for the previous week, writes SPF. And even if this variant does not seem more virulent, if it spreads quickly to many people, it will mechanically increase the number of patients in the hospital.

“It is not more severe than the other Omicron BA.1 or BA.2 variants, it is at the same level. But there are more cases so we have to deal with it”, underlines Alain Fischer. “When there is a wave, there is a certain degree of warning signal because inevitably, some of the infected people will go to the hospital”.

Especially since health professionals have warned of a lack of staff to come this summer, which could quickly lead to the saturation of certain services in the event of an increase in hospitalizations. The health authorities therefore encourage respect for barrier gestures and vaccination of the most fragile in order to avoid serious cases.

“We are vaccinated, we have strong collective protection, we know the variant that is in circulation, we know the means to protect ourselves from an epidemic outbreak – the mask, the barrier gestures… – the French know everything that”, declared the ex-minister of Health Olivier Véran this Wednesday on BFMTV / RMC, declaring not to have an “excessive concern” on this subject.

Salome Vincendon

Salome Vincendon BFMTV journalist

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