Should we be worried about the epidemic of the new variant of Mpox, also called “monkey pox”? Detected in the Democratic Republic of Congo (DRC) in September 2023, the disease has since spread to several neighboring countries. The African Union’s health agency, Africa CDC (Africa Centers for Disease Control and Prevention), has already sounded the alarm over the recent spread of the virus. The World Health Organization (WHO) announced on Saturday, August 10, that it will convene its emergency committee on Wednesday, August 14. “It will probably declare a public health emergency of international concern next week,” predicts Yazdan Yazdanpanah, professor of infectious and tropical diseases at Bichat Hospital and director of ANRS infectious diseases. This would then be the highest alert that the WHO can trigger.
Mpox is not a new disease. It was first discovered in humans in 1970, in what is now the DRC. The first form of this pathology was limited to the countries of West and Central Africa for a long time. The virus is transmitted by animals, probably a squirrel that lives in Central and West Africa. The clinical symptoms are fever, swollen lymph nodes, and skin rashes that sometimes cause lesions resembling moderate forms of chickenpox. This classic African form is most often transmitted to children, then to families through close contact, giving rise to small outbreaks of sporadic infections. The R0 of the disease, which indicates the average number of new cases that an infected and contagious person will generate on average, is 0.5 to 0.6. This explains why there has never been a large-scale epidemic.
There are two variants of the virus, the first, called clade 1, is present in Central Africa. The second, clade 2, is present in West Africa. “They are both responsible for classic forms of the disease,” says Antoine Gessain, professor at the Pasteur Institute and specialist in this disease.
But in 2017, researchers discovered a new form of the disease in Nigeria. It spread, affecting almost exclusively male homosexual populations. During this spread, the virus mutated and a new variant, called clade 2-B, appeared. It then spread to many countries around the world in 2022, including France. This time, the R0 was higher, between 1 and 2. Nearly 90,000 cases were recorded and 150 to 200 people died, mainly in patients with severe HIV-related immunosuppression. But the pandemic stopped, in particular thanks to prevention campaigns, the distribution of the drug tecovirimat, as well as the vaccination of at-risk populations with the smallpox vaccine. “There is cross-reactivity: even though they are two different diseases, the smallpox vaccine is about 80% effective against Mpox,” says Professor Antoine Gessain. The health emergency was therefore lifted in May 2023.
A fatality rate of between 5 and 10%?
Today, the disease has taken on a new form in Central Africa. “What we are facing is linked to a viral variant called clade 1-B,” says Prof. Gessain. This new strain was first detected in September 2023 in a major outbreak in South Kivu, a mining region in eastern DRC.A scientific study published in Nature Medicine last June reported several hundred cases and specified that it is a virus that is transmitted primarily through sexual contact in at-risk populations, particularly local sex workers,” notes Professor Gessain.
Clade 1-B seems, in any case, to have adapted to humans, in the same way as clade 2-B which caused the 2022 epidemic. This new variant has already contaminated at least several hundred people in the east of the DRC and has spread to provinces that were not previously affected. Above all, it has recently affected four neighboring countries. “There have been around fifty cases detected in Rwanda, Burundi, Kenya and Uganda. Clade 1-B has been sequenced in three of these four countries, which was the origin of the current WHO alert,” says Professor Yazdan Yazdanpanah. This is worrying, especially since the new strain could have a mortality rate of up to 5% in adults and 10% in children.
In parallel with this clade 1-b epidemic, another one is raging, the majority of cases of which are linked to the classic form of Mpox. “Between 12,000 and 14,000 cases have been recorded and 511 deaths, of which 70% of cases and 88% of deaths concern children under 15 years of age,” specifies Professor Antoine Flahault, epidemiologist at the Institute of Global Health in Geneva (Switzerland). “But this large number of cases is probably linked to a better knowledge of the disease and an increase in detection. The WHO alert is caused by the new clade 1-B variant,” specifies Professor Gessain.
The risk of European contamination is “very low” for the moment
Is a new pandemic inevitable, even reaching Europe? And if so, should we be concerned about the severity of this form of Mpox? “If the 2022 clade 2-B epidemic was so well controlled, it is because it affected a particular population – almost exclusively homosexual or bisexual men – already very mobilized and aware of fighting this type of transmission,” says Professor Flahault. Not to mention that vaccination was offered to them as a priority. “But if the mode of transmission concerns everyone, we change scale, it becomes more complicated to manage,” he adds. “And if it turns out that clade 1-B is also transmitted through the respiratory tract, this would increase the risk of large-scale spread.”
“It is said that the disease is more transmissible and more deadly, but is it the virus itself that is more transmissible, or is it the conditions on site that favor its transmission, particularly through numerous sexual contacts? We are not yet sure,” tempers Professor Gessain, who develops a similar reasoning for lethality. “Most victims do not die from the virus, but from severe bacterial skin superinfections – particularly in malnourished children – due above all to the lack of appropriate medical care (antibiotics, rehydration), since the people affected are often in remote and poor regions,” he emphasizes. And 30% of the population at risk, namely sex workers, is affected by HIV. However, Mpox can be fatal if HIV is poorly treated, which is sometimes the case in the DRC. Almost all of the European deaths during the 2022 Mpox epidemic were, in fact, men with HIV who were poorly treated.
In any case, the situation has not yet changed and could be contained. “The risk of the extension of this clade 1-B is considered very low at the European level, confirms Dr. Yazdan Yazdanpanah. Stopping the epidemic is not impossible, but we must act quickly.” Above all, if it reached us, its treatment could be much more easily managed than in Africa. An analysis shared by the two other researchers, who especially fear a local increase in cases. “We are not at the pandemic stage, but what Covid and HIV have taught us is that the sooner we intervene, the better,” insists Professor Flahault. It is important that politicians take hold of the subject: we know about pandemics, and we know that we do not want them.” The three researchers therefore insist on the solutions to be implemented: increasing human, logistical and financial resources, in particular a massive investment to bring the vaccine and treatments to the populations, but also improving screening, diagnostics, patient care and information to the populations.
A first plan of 15 million dollars
Everyone hopes that the WHO will declare a health emergency, and regrets that it is so late. “Unfortunately, every time a disease emerges in sub-Saharan Africa, we have difficulty triggering alerts that match the commitment required,” laments Professor Flahault. The expert stresses the importance of not only providing one-off aid, but also investing to provide long-term resources so that these African countries can become self-sufficient in the production of vaccines, diagnostics and tests.
WHO has, for its part, developed a regional action plan that requires $15 million (€13.7 million) to support surveillance, preparedness and response activities. On Friday, August 9, it invited vaccine manufacturers to submit an “expression of interest” to be included in the Emergency Use Listing (EUL). Manufacturers wishing to participate will have to submit dossiers proving that their vaccines are safe, effective, of quality and suitable for the target populations. Granting an EUL will then accelerate access to vaccines, particularly for low-income countries, by authorizing the purchase and distribution of vaccines by WHO partners such as UNICEF.
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