Covid-19: Study finds 10% infection rate in France

A new study released by research centre l’Institut Pasteur indicates that 10% of people in France have already been infected with the Covid-19 virus.

The study also showed that the number of people infected varies significantly from region to region.

The regions with the highest percentage of infections are the Ile-de-France (21.3%), Grand-Est (15,2%), and Auvergne-Rhône-Alpes (14.3%). Meanwhile in Brittany, only 3.6% of the population have contracted the virus.

These figures could have a significant impact on reducing its spread.

In a population where no one has been in contact with the virus, an R-number of 2 means that ten infected people will infect twenty others. But, if one in four people are potentially immune to the virus, the R-number drops to 1.5. This means those ten infected people will now only infect 15 others.

However immunity through infection has not yet been proved and does not remove the risk of future waves of the virus.

Dr Simon Cauchemez, one of the authors of the study and a member of government advisory body le Conseil Scientifique, told newspaper Le Monde: “In all regions there is a risk of a significant third wave. We must stay vigilant, everywhere.”

Will numbers improve enough for deconfinement on December 15?

In a speech last week, President Macron said that confinement measures would end on December 15, and be replaced with a curfew, if the spread of the virus has slowed sufficiently.

The President said that for deconfinement to go ahead, daily contaminations should be down to 5,000 a day in France and there should be a maximum of 2,500-3,000 Covid patients in intensive care.

Currently there are just under 3,500 Covid patients in intensive care, and figures from December 3 show there were 12,696 new cases in the previous 24 hours.

But forecasts from the study suggest meeting the targets is possible. It predicts that on December 15, 1,600-2,600 critical-care beds will be occupied by Covid patients in intensive care and continued surveillance wards.

It is also expected that the target of fewer than 5,000 infections per day will be reached, although this is less certain.

Dr Cauchemez said: “In the past few days we have the impression that the decrease in contaminations is starting to slow. If this is the case, the date will be pushed back.

"Additionally, it is possible that all the cases detected with rapid antigen tests have not yet been recorded in the data, which would give us an over-optimistic outlook.”

Researchers at l’Institut Pasteur also expect the R-number to rise throughout France as a result of non-essential shops being allowed to open since November 28. At the end of November, the R-number was 0.8, but by mid-December it is expected to be 1.1.

Study conducted in complicated conditions

Dr Cauchemez also spoke about the difficulty of conducting such a study, saying that it was impossible to evaluate the exact spread of the virus as different measures such as curfews and restaurant closures are implemented.

“What matters the most is the way in which people apply measures and change their behaviour, which is difficult to see in the data,” he said.

An additional factor is uncertainty over how long patients with Covid are staying in hospital.

The average stay is estimated to last 14 days, but can be much longer in reality.

Dr Cauchemez said: “At the end of a wave of the virus, the only patients left in hospital are those who have been there for a very long time.”

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