New variant of mpox detected in Brittany: what we know

What do we know about the first case of clade 1b detected in Rennes?

On Monday, the Ministry of Health indicated that it had been informed of “a first human case of clade 1b mpox on the national territory, in Brittany”, confirming information from Ouest-France. The patient concerned was hospitalized at Rennes University Hospital. The health authorities clarified that she “did not travel to central Africa, an area in which the different clades of mpox viruses have been actively circulating for several months, including clade 1b. This person, however, was in contact with two people returning from central Africa.”

According to our information, the patient, in her thirties and living in the Rennes region, only experienced mild symptoms and is now cured. All his contacts have been screened and vaccinated, according to the planned indications. “We have good reasons to think that this will just be a unique case in the territory, without secondary transmission,” confides a source close to the matter to Télégramme. This was confirmed by the Minister of Health, Yannick Neuder, during a visit to Rennes this Tuesday morning: “There is no reason to think that there would be other sporadic cases. In any case, none has been brought to our attention. And if there is, a very clear strategy is established in conjunction with the WHO, Europe and Public Health France.”

Which countries are most affected by this new variant?

Before France, four European countries had recorded cases of clade 1b mpox on their territory since August 2024: Sweden, Germany, the United Kingdom and Belgium. In its press release, the Ministry of Health notes that “sporadic cases, linked to countries with more intense viral circulation, may occur” but that “the risk of infection by clade 1 (including clade 1b) of mpox for the general population in France and Europe is considered low by the European Center for Disease Prevention and Control (ECDC).”

For its part, the World Health Organization decided, on November 22, to maintain its highest level of alert in the face of “the resurgence of mpox” which “continues to constitute a public health emergency of international concern”. The Democratic Republic of Congo (DRC) is the most affected country, with more than 38,000 suspected cases and more than 1,000 deaths reported in 2024.

Long confined to Africa, mpox has managed to generate a global epidemic in 2022, via its 2b variant. Since then, it has been circulating quietly in France. “In 2024, 215 cases of mpox were declared”, counted Public Health France. Five were detected in Brittany. Only 6% of French patients had to be hospitalized.

Is this new variant more dangerous?

Mpox is characterized by skin lesions, high fever and muscle pain. It is transmitted by contact with these lesions, fluids and mucous membranes. Clade 1b is considered “possibly more transmissible” by scientists. The Pasteur Institute also notes that “lethality seems greater with the Central African strain (clade 1) and in an endemic context”. The case fatality rate was between 3 and 6% in Africa during the 2022 epidemic, according to the WHO, but it varies greatly depending on the age of the patients or the quality of hospital care.