These are 92 confirmed contaminations and a large unknown.
The World Health Organization (WHO) returned for the first time, Saturday, May 21, to the multiplication of cases of monkeypox in the world.
The institution has confirmed the presence of this disease in twelve countries outside Africa, which was until now the only continent to have experienced monkeypox epidemics.
Portugal, Spain and the United Kingdom are the main centers of spread with more than 20 cases each, while France confirmed the first positive diagnosis on Friday May 20.
This disease is a zoonosis - transmitted to humans by animals - identified for the first time in monkeys in the laboratory in 1958 and which belongs to the same family as chickenpox or smallpox.
Much less deadly than the latter, monkeypox currently exists in two forms: one which has spread mainly in the Democratic Republic of Congo and Congo-Brazzavile, and the other further west of the continent, mainly in Nigeria.
“It is this second, less dangerous strain that is currently found in Europe and North America”, specifies Matthias Altmann, epidemiologist at the University of Bordeaux and specialist in infectious diseases in Africa.
Most of the time, the symptoms of the virus - fever, cough, headache and rash - disappear on their own after a few weeks and none of the patients recorded in Europe and North America have died from the disease.
No direct link with a country where the virus is endemic
If the origin of this virus is well known, what currently worries scientists is "that a majority of cases of monkeypox had no direct link with an African country where the situation of this virus is endemic , which is very unusual,” notes the WHO.
“There is an autochthonous transmission of the virus which we had not yet faced with this disease and which we cannot explain”, confirms Charlotte Hammer, specialist in infectious diseases at the University of Cambridge, questioned by the Science Media Center website.
Until now, this virus only very exceptionally came out of Africa, and when that happened, it was very easy to find a link.
“There were dozens of cases in the United States in 2003 that were linked to a rodent carrying the virus that came from Africa. In 2018, a British nurse was exposed to this disease in hospital while changing sheets from the bed of a patient who had been infected in Nigeria," said Paul Hunter, professor of medicine at the University of East Anglia.
If monkeypox is transmitted little and it is generally easy to trace the chain of contamination, it is because this disease "is much less contagious than Covid-19, because it generally requires direct and close contact with a carrier", summarizes Matthias Altmann.
For the European Center for Disease Prevention and Control (ECDC), this is also one of the main reasons why “the probability of contagion is very low”.
“We also think that it is transmitted after the appearance of the first symptoms”, specifies Matthias Altmann.
The main vectors of contamination of monkeypox are "the blisters and sores on the face, hands and feet that appear in an infected individual", emphasizes Paul Hunter.
Nothing to do with the silent spread of Sars-Cov-2, amplified by asymptomatic carriers, which has made the pandemic so difficult to control.
Fewer vaccinated against smallpox
This is why the current explosion of monkeypox cases around the world has taken the scientific community by surprise.
An element of explanation comes "from the continuous increase in the number of cases of contamination on the African continent in recent decades, which made an export of the virus become more and more probable", notes Matthias Altmann.
An increase due, in turn, to an ever-increasing number of people who are not or no longer protected against this family of viruses.
“The vaccine used to protect against smallpox is also effective against monkeypox. in fewer people vaccinated and immunized in the world", underlines Paul Hunter.
But you still need one or more trigger(s) that would promote borderless propagation.
In Spain, one of the most affected European countries with 30 confirmed cases, authorities are currently investigating whether a festival that took place in early May on the island of Gran Canaria could be one of the main sources of contamination. , explains the German daily Süddeutsche Zeitung.
More than 80,000 people gathered there for ten days to party and Italians, Madrid residents and residents of the neighboring island of Tenerife were then infected with monkeypox.
Mutation unlikely
In this quest to understand this rise in cases around the world, another element has emerged that has surprised scientists: the sex factor.
Currently, “most, but not all, cases are in men who have had sex with men,” the WHO notes.
"This is the first time I've heard of transmission during sex for monkeypox," admits Paul Hunter.
But "we must be very careful not to speak of a sexually transmitted disease yet", insists this specialist.
After all, contamination occurs during direct contact with an infected area, which is more likely to occur during intimate intercourse.
The multiplication of contaminations could also "be due to the fact that it may be a mutation of the virus which would be more contagious than the original strain", notes Matthias Altmann.
The evolution of Covid-19 has shown how variants can change the face of a pandemic.
But monkeypox is very different from Sars-CoV-2 in this respect.
"Even if the hypothesis is not impossible, this family of viruses - large DNA viruses - is much more stable and mutates less often than RNA viruses such as Sars-CoV-2", specifies Matthias Altmann.
In addition, Portugal has undertaken to sequence the genome of the strain currently circulating in Europe and "it would be identical to that which is active in West Africa", adds this expert.
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