The World Health Organization (WHO) is changing gear. On Wednesday, August 14, it triggered its highest alert level in the face of the resurgence of cases of MPOX – formerly called monkeypox – on the African continent, due to the appearance of a new variant.
Since then, Sweden has reported an imported case of this variant on its territory. While others are likely to be detected soon in Europe, France is in turn placing the health system in a “state of maximum vigilance”, announced Prime Minister Gabriel Attal on Friday, August 16. Here are the answers to the most frequently asked questions.
What is mpox?
It is a viral disease. “It is of zoonotic origin. That is to say that in the wild, it is an animal that serves as a reservoir for the virus, probably a squirrel,” says Professor Antoine Gessain, head of the epidemiology and physiopathology of oncogenic viruses unit at the Pasteur Institute, and a specialist in the disease. Typically, the classic African forms of the disease are the result of the passage from animals to humans.”
The child, after playing with an animal, may contaminate those close to him. But the epidemic outbreaks die out fairly quickly. This is therefore the classic – and historical – case of the disease. But cases of exclusively human-to-human transmission have emerged. This is what is of concern today.
Is this the same virus as during the 2022 pandemic?
Not quite. Two clades – meaning two variants of the virus – have historically been identified. Clade I is widespread in Central Africa. Clade II is rampant in West Africa. While it was the second version of the virus that gave rise to the pandemic in 2022, the first is currently causing alarm in Africa, but in the form of a new variant. The virus mutated because it made a “jump” and spread massively in the human population, freeing itself from the animal world.
The victims of this clade, called Ib, have changed. Now, adolescents and adults are affected. The first cases were detected in September 2023 in a mining area in the east of the Democratic Republic of Congo (DRC), among sex workers and their clients, men working in the mine. Since the end of 2023, cases of this new variant have been detected outside the borders of the DRC. And so since Thursday, August 15 in Europe.
How is MPOX transmitted?
“Contamination between humans occurs through the skin, through contact with vesicles on the skin and their fluids containing the virus,” continues Professor Gessain. Clade Ib, which is the driving force behind the epidemic, is transmitted mainly through sexual intercourse and contact between skin and mucous membranes. We can read here and there that contamination through the air – through microdroplets of saliva – is possible. This is not the case.
What are the symptoms?
Sometimes, there is none. “The virus can be present in the body, but not cause symptomatic illness,” says Karine Lacombe, infectious disease specialist and head of the infectious diseases department at Saint-Antoine Hospital, Sorbonne University. After an incubation phase, the first signs may appear. “It starts with a flu-like syndrome: a high fever, aches, sore throat. Then adenopathies, that is to say disseminated lymph nodes, she adds. After a few days, a rash appears, which leads to vesicles that disappear in two to three weeks, without leaving scars.” Severe pain may also be present. During the 2022 pandemic – the dynamics of which were also multi-partner sexual intercourse – the mode of contamination gave rise to lesions on the mucous membranes (mouth, genital and anal regions).
African cases mediated by clade Ib seem to give a similar clinical picture. “We know practically nothing about the Swedish case,” Professor Lacombe cautiously points out. The risks of complications are of two types. “First, what is called sepsis, an extremely significant inflammatory reaction due to the overflow of the immune defenses by the virus. And then the bacterial superinfection of the skin lesions.”
Is this new variant of mpox more “nasty”?
Not sure. “According to clinical data that we have in Africa, it would seem that it is more contagious and that people who contract it are sicker,” reports Karine Lacombe. Who insists on the conditional. “These data are quite complicated to interpret. Because there is little screening in Africa. It is really difficult to calculate an incidence. But if we compare clade I, historically present in the DRC, and clade II in West Africa, the former still presents a higher mortality rate.”
It is also difficult to extrapolate what is happening in Africa to what could happen in Europe. Access to treatment and the health of populations are better in the West. “MPOX remains a disease of socio-economically difficult areas and often occurs in remote areas where medical care is not effective. In these areas, children – often malnourished and sometimes, in addition, dehydrated – pay the heaviest price for this disease with deaths linked to bacterial superinfections of skin lesions. Other deaths occur in people immunocompromised by HIV, especially if they are poorly or poorly treated,” emphasizes Professor Gessain.
What are the treatments for COPD?
There is an antiviral, tecovirimat, an inhibitor of the virus cycle in the cell. Is it effective? It is currently being evaluated in Europe, particularly in France in a clinical trial called Unity. “For the moment, we have only included 250 patients during the 2022 epidemic,” explains Professor Karine Lacombe. “These are not enough subjects to draw any conclusions.” A similar trial is underway in the United States, but there too it is too early to comment on the effectiveness of the molecule. And then the Western cases are from clade II.
The only data on the benefit of tecovirimat on clade I comes from a therapeutic trial conducted on children in Africa. “The results showed that it did not work,” reports the infectiologist. Cases of clade I would still be treated with tecovirimat in France, in order to enrich scientific knowledge on the drug. In addition to rehydration care, painkillers and antibiotics – in the event of bacterial superinfection – possible.
How to protect yourself from MPOX?
Contaminated people must isolate themselves. In case of risk, it is possible to receive a dose of post-exposure smallpox vaccine. Since the two viruses are similar, stimulating the immune system against smallpox protects against MPOX in two-thirds of cases. At Saint-Antoine Hospital, the strategy is now well-established. When a case of MPOX is detected, vaccination is systematically offered to those around them and to sexual partners.
