Monkey pox: an expert from the Institut Pasteur deciphers a “really unusual” disease

The smallpox of the monkey continues to progress in France And in the world. At the last count, 91 cases were confirmed in France and almost as many are under investigation. In order to have all the keys to understanding this disease, its emergence and its management, Futura spoke with India Leclercq, teacher-researcher at the Biological Emergency Response Unit of the Institut Pasteur and at the University of Paris-Cité. Together with her colleagues, she studies and monitors emerging infectious diseases in France and responds to biological emergencies 24 hours a day, 7 days a week.

Do we know where the strain of monkeypox that has been circulating outside Africa since the beginning of May comes from?

India Leclerq : Recently, we obtained a number of complete sequences of the genome. Even if the data must be consolidated, the first analyzes suggest that the strain currently circulating in regions not endemic is similar to that which circulated in 2017-2018 in Nigeria and which was at the origin of a notable epidemic episode. Moreover, at that time, there had already been a few cases of importation into non-endemic regions.

The number of monkeypox cases outside Africa is unprecedented. Is this a sign that this strain is more transmissible than the others?

India Leclerq : It’s really unusual, there have never been so many cases outside of Africa. But it is still a bit early to say that the strain is more transmissible than the strains circulating in West and Central Africa. We need a little more epidemiological data to better characterize the dynamics of transmission and circulation of virus. Given the direct contact and respiratory droplet mode of transmission, the number of cases globally is still relatively low. This suggests that the strain circulating today is not necessarily more transmissible than the one spreading in Africa.

Is there a mode of sexual transmission of the disease as some media claim?

India Leclerq : It all depends on what you call sexual. We have no data to say that the virus is transmitted through semen and vaginal fluids. However, it is transmitted by close contact. When you kiss, caress someone, you have close contact and therefore potentially a transmission. Sexual intercourse can actually promote the transmission of the virus. The homosexual community has been stigmatized a lot, but any sexual relationship can promote transmission, whether heterosexual or homosexual.

How is the evolution of cases in France monitored?

India Leclerq : The monkeypox virus was already under surveillance, and identified as potentially emerging. The disease is now reportable. It is therefore necessary to refer to the health authorities as soon as a case is confirmed for the monkeypox virus. It allows you to quickly track infected people and then afterwards, there is a whole system of information and large-scale alerts. There are messages that are addressed to health professionals, precisely to warn about this new disease, let’s say rather about this disease relatively unknown to doctors at the present time.

Cases are diagnosed quickly in order to allow the isolation of infected people and to avoid the spread as much as possible. We think that the virus circulated quietly, a little under the radar for several months. Doctors are more knowledgeable now about this relatively rare condition which can be easily confused with varicella or the syphilis. It is very likely that there were unidentified cases of monkeypox.

The smallpox vaccine is also recommended by the Haute Autorité de Santé to limit the spread of monkeypox.

India Leclerq : Yes, it is recommended in post-exposure. It is effective if it is administered within four days of the onset of symptoms, it is still necessary to be vaccinated fairly quickly and the strategy adoptedI believe, is that of the vaccination in a ring, that is to say vaccinate infected people and very close ones to limit the spread of the virus and contain the source of infection more quickly.

Besides, are people immunized against human smallpox protected against monkeypox?

India Leclerq : Very likely since the vaccine against smallpox would protect between 80 to 85% against infection, so people who have been vaccinated against smallpox are more or less protected against monkeypox virus. And besides, when we look at the age group of the infected, they are mainly people between 20 and 50 years old, people who have not received a smallpox vaccine.

How are the sick cared for?

India Leclerq : At present, we only process the symptoms of the disease : first and foremost, skin lesions are treated to avoid secondary bacterial infections, and relieve pains of the patient. For immunocompromised people or young children, they are still very rare in theepidemic current situation, more advanced treatments can be recommended. Of the antivirals exist, but they are directed against the smallpox virus.

Finally, the question everyone is asking: could the monkeypox virus cause a global pandemic?

India Leclerq : I don’t have a crystal ball. When we refer to what theWorld Health Organization, it assesses global risk as moderate. The circulation dynamics are not the same as during the Covid-19. With le SARS-CoV-2we had a virus that was transmitted by air, but over a long distance and that was extremely contagious. At present, people infected with the monkeypox virus transmit it mainly when symptoms have appeared. The asymptomatic are very little contagious.

Control measures are therefore much simpler to put in place. Once the person develops symptoms, it is easy to isolate them. This was not the case with the SARS-CoV-2. In addition, there is a vaccine and antivirals already ready, which are not specific to the virus, but which have nevertheless shown their effectiveness. It is also a virus which mutates less a priori than an RNA virus, the viruses DNA being less prone to mutations. Let’s be careful, viruses are unpredictable by nature.