The European Union delivered this Thursday, September 5, to the Democratic Republic of Congo a first batch of 99,000 doses of vaccines against Mpox, in a country where the epidemic is wreaking havoc: more than 19,000 cases and 650 deaths since the beginning of the year. Scientists from ANRS Emerging Infectious Diseases, an offshoot of Inserm, and IRD reassure about the risk of an epidemic in France, even if many unknowns remain.
“A lot of nonsense has been said about Covid, but I don’t think there is any reason to worry. There are treatments, vaccines… and over the past two years, we have had time to mark out the care pathway.” : Éric d’Ortenzio, doctor, epidemiologist and head of the strategy and partnerships department at ANRS Emerging Infectious Diseases (MIE), wanted to be rather reassuring about the risk of an Mpox epidemic in France, this Thursday, September 5, during a press conference organized the day after the announcements by the Ministry of Health aimed at strengthening the vaccination strategy.
Effectiveness of vaccines, treatments, progress of the epidemic, situation in Africa and Europe, scientists from ANRS-MIE and IRD took stock of the situation, while the first doses of vaccine arrived that same day in the Democratic Republic of Congo, the epicentre of the epidemic affecting several African countries, notably Burundi, Congo-Brazzaville and the Central African Republic.
The epidemic “mainly in Africa”
“The epidemic is mainly located in the Democratic Republic of Congo and neighboring countries”it is linked to the circulation of the clade virus (which can be translated as “strain”) 1b of the virus, underlines Professor Yazdan Yazdanpanah, at ANRS-MIE.
On August 14, the head of the World Health Organization (WHO), Dr.r Tedros Adhanom Ghebreyesus, had declared “a public health emergency of international concern” in the face of the surge in the number of cases in Africa, “The number of cases reported so far this year has already exceeded last year’s total, with more than 15,600 cases and 537 deaths”specifies the WHO.
“We have more than 19,000 cases and 650 deaths this year”says Dr. Placide Mbala, head of the epidemiology and global health department and head of the pathogen genomics laboratory at the National Institute for Biomedical Research (INRB) in the DRC, with extensive experience of Mpox: “MPOX has existed in the DRC for over 50 years, but the disease has always remained confined to forest regions”.
Mode of transmission, clades, risks, situations differ depending on the country, one year after the appearance of clade 1b, identified in 2023, while the year 2022 had seen the emergence, mainly in Nigeria, of clade 2, and caused a first global epidemic. It is clade 2 which circulates almost exclusively in Europe and France, with no deaths to date: “Since January 1, 2024, a total of 143 cases of Mpox clade 2 infection have been reported to Public Health France, including 14 in the last seven days,” SPF said in a press release published this Thursday.
France wants “prevent the emergence of clade 1b” on its territory, “in accordance with the opinion of the High Authority of Health” (HAS) of September 2, 2024. To date, a single case of Mpox 1b has been identified in Europe, in Sweden. There is also a case in Thailand, and investigations are ongoing.
Clade 1 or clade 2, the distinction is not trivial: viruses are not equally contagious and dangerous. “Mortality varies from 3.5% to 6.8% for 1a”says Placide Mbala.
Vaccination imminent in Africa, recommended for at-risk groups in France
It will take a few weeks to organize the vaccination, which should start next month in the DRC. “A vaccination plan has been put in place. Health workers, sex workers, MSM, men who have sex with men, transgender people, and children aged 1 to 17”on the front line (four deaths out of five), are a priority, specifies Placide Mbala. Veterinarians and hunters, in contact with the animals, also.
Protection is essential because “the epidemic has changed” of face, recalls Martine Peeters, research director at the IRD in Montpellier: it was a zoonosis (transmission from humans to animals), it has become a disease transmissible from human to human. Today, several epidemics overlap.
In France, “The people targeted by preventive vaccination are men who have sex with men reporting multiple partners, transgender people reporting multiple partners, people in prostitution and sex workers, professionals in places of sexual consumption”.
If the disease “resembles smallpox, with fever, rash and very painful lesions, especially on the mucous membranes”, Professor Xavier Lescure, Inserm researcher and doctor in the infectious and tropical diseases department at Bichat hospital, recalls the risk of complications: “Bacterial superinfections that can affect the eyes, serious forms with encephalitis and myocarditis, dehydration in toddlers.”
Children and immunocompromised people are on the front line.
Tests are underway.
“The currently authorized vaccine was developed to prevent smallpox. Repositioned on Mpox, it increased its effectiveness, and I am not sure that a vaccine specific to Mpox should be developed”says Dr. Liem Binh Luong Nguyen, an infectious disease specialist at the clinical investigation center for vaccinology at Cochin Hospital. According to him, “the level of neutralizing antibodies that prevent the virus from multiplying, drops quite quickly after a year”. He recommends “to get vaccinated every two years”, “it’s not dangerous”. But “many people at risk have not been vaccinated”.
“Effective treatments”
“Treatments save lives, it is crucial that patients know this”insists Professor Alexandra Calmy, infectious disease specialist, head of the HIV/AIDS unit at the Geneva University Hospitals.
An antiviral drug used against smallpox, tecovirimat, is in the front line. It remains to be seen whether it “It must be combined with other treatments” for greater efficiency.
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“The monkey is not considered a reservoir host of the virus, we are thinking more of rodents”says Eric d’Ortenzio.
This is not the only mystery for researchers to solve: “Little is known about the characteristics of the virus,” adds Montpellier resident Martine Peeters, who worked with Placide Mbala on “samples from 600 symptomatic patients” from the DRC, in 2023, “contain more than 80% of clade 1a strains”.
On the transmission mode: “Respiratory transmissions are very marginal”insists Xavier Lescure, who also remains unclear about the transmission routes among sex workers and in the homosexual community: “We don’t know if it’s just sexual intercourse, or skin-to-skin contact.”
