A patient identified in Rennes
The Ministry of Health has confirmed that a woman hospitalized at Rennes University Hospital has the new mpox variant. This isolated case is the first identified in France and was quickly treated. The patient had not traveled to Central Africa, but she was in contact with two people returning from this region, known to be a focus for the spread of clade Ib. An epidemiological investigation is underway to understand the chain of transmission.
This variant, first detected in the Democratic Republic of Congo at the end of 2023, has since spread to other African countries before reaching Europe. Several cases were reported in Sweden, Germany, the United Kingdom and Belgium, before this first diagnosis in France.
The specifics of the variant clade Ib you virus mpox
The variant clade Ib of the mpox virus, recently detected in France, presents several specificities which differentiate it from other clades, in particular clade IIb, which had widely circulated in Europe in 2022-2023. Here is an overview of the main characteristics of this variant:
1. Geographic origin and spread
- Origin : Clade Ib was first identified in the Democratic Republic of Congo (DRC) in late 2023, where it caused an epidemic resumption. It is associated with increased circulation in several Central and West African countries.
- Propagation : Unlike clade IIb, mainly observed in Europe and North America, clade Ib has been reported in regions with limited health infrastructure, facilitating its initial spread. Since then, it has reached several European countries (Sweden, Germany, United Kingdom, Belgium) before being detected in France.
2. Transmissibility rate
- Higher transmission : This clade appears more transmissible than clade IIb. This could be due to genetic characteristics favoring its spread, although the exact mechanisms are still being studied.
- Methods of transmission : The virus is transmitted mainly by close contact (skin to skin), including during sexual intercourse, but also via contaminated objects and, potentially, by respiratory droplets.
3. Severity and mortality
- Mortality rate : Clade Ib is associated with a mortality rate of approximately 4 %according to data from the DRC. However, this figure mainly reflects contexts where access to care is limited and could be overestimated due to insufficient screening.
- Clinical manifestations : Symptoms are similar to other clades (fever, skin lesions, fatigue, muscle pain), but some preliminary studies suggest that skin lesions may be more extensive in some patients.
4. Resistance to treatments
- Reduced effectiveness of Tecovirimat : A study from Africa indicates that the antiviral treatment Tecovirimat, used for other mpox variants, may be ineffective against clade Ib. This raises concerns about treatment options for severe cases.
- Vaccines : Smallpox vaccines used against clade IIb are expected to provide similar protection against clade Ib, although additional studies are needed to confirm their effectiveness.
5. Populations at risk
- Populations at risk include those already identified for clade IIb, including:
- Men having sex with men.
- Sex workers and people frequenting places of sexual consumption.
- People in close contact with confirmed cases.
- However, epidemics in Central Africa show that this clade can affect rural and urban populations more widely, independent of these factors.
6. International response
- In August 2024, WHO declared a public health emergency of international concern due to the rapid spread of clade Ib. This declaration aims to coordinate global efforts to contain this variant, particularly in areas where the virus is endemic .
Clade Ib presents worrying specificities, such as increased transmissibility and potential resistance to certain treatments, but European health systems, and in particular French, are well equipped to limit its spread. Reinforced vigilance, rapid screening and targeted vaccination are essential to control this new variant.
A situation under control according to Professor Verdon
According to Professor Renaud Verdon, specialist in infectious and tropical diseases at the University of Caen Normandy and Caen University Hospital, “the current situation in no way justifies widespread concern, just vigilance”. Professor Verdon recalls that France has solid surveillance mechanisms allowing rapid detection and effective management of cases. This Breton case, although notable for its rarity, is part of a context of health control thanks to adapted measures.
-Professor Verdon also specifies that the disease, although it can cause annoying symptoms (fever, skin lesions, muscle pain, fatigue), remains under control. Until now, clade IIb was the only one in circulation in France, with 200 confirmed cases in 2024. The appearance of clade Ib, which is more transmissible, justifies increased vigilance but should not cause a generalized epidemic, in particular thanks to prevention efforts deployed.
Reinforced prevention measures
To limit any risk of spread, health authorities have strengthened prevention measures. These include:
- Targeted vaccination : people at high risk (men who have sex with men, sex workers, professionals at places of sexual consumption) and contacts of confirmed cases are invited to be vaccinated.
- Epidemiological surveillance : rigorous monitoring of suspected and confirmed cases helps prevent any spread.
- Specific measures for travelers : Current recommendations target people returning from regions where the virus is actively circulating. They include advice to limit the risk of exposure.
Necessary vigilance, but no alarmism
Professor Verdon points out that the emergence of this clade Ib in regions such as the DRC and Sierra Leone has led the World Health Organization (WHO) to declare a public health emergency of international concern. However, in Europe, and particularly in France, the risks for the general population are considered low.
Health authorities continue to monitor the situation and issue appropriate recommendations, particularly for travelers going to risk areas. The High Council for Public Health (HCSP) has also issued opinions to strengthen prevention measures internationally and among health professionals.
The appearance of clade Ib in France is a reminder of the importance of mechanisms for surveillance and prevention of infectious diseases. The rapid treatment of this first Breton case demonstrates the effectiveness of the French public health system. Although vigilance remains essential, experts agree that the risk of a major outbreak is limited. The general population can approach the situation with serenity while following the recommendations of the authorities.
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