Plans to make face masks compulsory in enclosed public spaces were brought forward on Thursday in the Finistere region of Brittany and Mayenne region near the Loire Valley after concerns over a spike in COVID-19 cases.
Western and southern France, both popular with tourists, were relatively spared during the height of the country's outbreak between March and May.
However, focus has now turned to those regions as the R number - a key measure of how fast coronavirus is spreading - in Brittany rose from 0.92 on 10 July to 2.62 by 14 July.
It means for every person infected with COVID-19, they will pass it on to between two and three other people, with a number of less than one needed to gradually contain the disease.
"It's a worrying number because it means the epidemic is taking off again," Professor Eric Caumes, an infectious disease specialist at the Pitie-Salpetriere hospital in Paris told BFM TV.
Brittany's regional health agency said the rising case numbers are also linked to a 50% increase in testing in the area over the past week, and said there are only three people in intensive care with the virus in the region.
More than 30,000 people have died with COVID-19 in France but the number of deaths and people in intensive care had been falling.
As the summer holiday season approaches daily cases have increased as people gather in larger groups and travellers have been allowed back into France.
Professor Caumes said Paris hospitals had not seen any new cases in June, but since the start of July two or three infected people a day have been coming in - a similar number to February.
"It is possible that what is happening in Paris is nothing compared to what is happening in other regions of France which were not hit by the first epidemic wave and risk facing an epidemic wave," he said.
The rest of France will have to wear masks in indoor public places from next week.
https://news.sky.com/story/coronavirus-cases-soar-in-frances-brittany-region-as-summer-holidays-begin-12030616