Transmission, number of cases… After Covid-19, will monkeypox be the next great pandemic?

Figures that worry. Since early May, more than 1,600 confirmed cases of monkeypox have been reported in 32 countries where the disease is not endemic. Less than a week after calling on states to “control the outbreak” of the virus, the Director General of the World Health Organization (WHO), Tedros Adhanom Ghebreyesus, on Tuesday ruled the extension of the epidemic “invalid “and worrying”, believing that “the situation requires a coordinated response”.

If at the beginning, only a few isolated contaminations were reported in the United Kingdom or in Portugal, the number of identified cases and affected countries quickly exploded and now, “the risk that monkeypox settles in non-endemic countries is real,” said WHO, which will convene a meeting of its emergency committee next week to assess whether the virus represents a “public health emergency of international concern.” So, like Covid-19, can monkeypox contagion turn into a pandemic?

A virus present on several continents

Uncovered in Wuhan at the end of 2019, the Covid-19 very quickly crossed the borders of China and spread across the globe in a few weeks. The first French case was identified in February 2020 and the following month, the WHO qualified Covid-19 as a pandemic.

Regarding monkeypox, the first non-endemic cases were identified as early as May 6 in the United Kingdom. The following days, other contaminations are reported in several European countries and in the United States. In France, the first case was identified on May 19. And today there are more than a hundred. According to the latest figures communicated on Tuesday by Public Health France, “125 confirmed cases have been reported in France, including 91 in Ile-de-France”. For the WHO, the “sudden and unexpected appearance” of the virus in non-endemic countries suggested that it had been circulating for some time, without its transmission having been detected. “As for Covid-19”, notes Dr Benjamin Davido, infectious disease specialist at the Raymond-Poincaré hospital in Garches (Hauts-de-Seine).

Does this mean that the planet is experiencing a monkeypox pandemic? ” You should be careful. But factually, we are facing a pandemic: the virus is present on several continents, and in a very unusual way, Europe is affected, notes the infectiologist. If from a geographical point of view, we are on a pandemic distribution, this is not yet the case on the side of the figures, he reassures. There is an increase in contamination, but we are not (yet) facing a galloping disease ”.

Modes of transmission and specific symptoms

Contamination by surfaces or by droplets: “we groped a bit before asserting that Covid-19 was transmitted mainly by aerosol, remembers Dr Davido. With monkeypox, we also groped to define the modes of transmission and the percentages they represent”. Like Covid-19, monkeypox is a zoonosis, a disease initially transmitted to humans by infected animals, wild or in captivity, dead or alive, such as rodents or monkeys.

Side symptoms, the two different viruses. “Where Covid-19 has caused concern with the risk of severe form and lung damage, monkeypox is not associated with any cases of pulmonary or neurological complications, and is characterized by appearance of skin lesions, describes the infectiologist. However, while many publications illustrate monkeypox with black people with lesions on their hands, the approximately 1,000 cases revealed in recent weeks mainly affected men who have sex with men (MSM) with lesions on the genitals. underlines Dr. Davido who, at the end of May, took charge of two affected French patients. An “ano-genital rash” present in “77% of the cases investigated”, indicates Public Health France.

The particularity of these non-endemic cases is based on “their unprecedented mode of sexual transmission, by direct contact with the skin lesions or the mucous membranes of a sick person. And all the cases present lesions located exclusively at the genital level, continue Dr. Davido, author of an article to be published in the Travel Medicine Journal. We are therefore on a very different mode of transmission from Covid-19, with a much slower speed of propagation. And if like Covid-19 (since the massive vaccination campaigns), the disease has a fairly low lethality rate, of less than 1%, it remains very distressing for the sick. One of my patients said to me: “I am afraid of losing my penis”.

Vaccines available, but…

Fortunately, a vaccine against human smallpox offers cross-immunity against monkeypox “with a high level of efficiency” of around 85%, reassured Sylvie Briand, director of the department of pandemic and epidemic diseases at WHO. At the beginning of 2020, while we are talking about the “new coronavirus”, no vaccine yet exists. It will be necessary to wait until the end of the year so that the first anti-Covid vaccines do not see the light of day – in record time – and begin to be administered.

But if laboratories have been able to produce millions of doses to protect against the coronavirus, to date, the WHO does not know how many doses of smallpox vaccine are available worldwide. The organization seeks to take inventory of stocks and contacts “manufacturers (of vaccines) to find out their production capacities” and distribution, said Sylvie Briand. And “we may not have enough vaccines, worries Dr. Davido. We do not know the state of the stocks, which includes the strategic reserve to deal with a bioterrorist threat”. But this Tuesday, the European Commission and the Danish laboratory Bavarian Nordic announced the conclusion of a contract for the purchase of more than 100,000 doses.

Unlike Covid-19, the WHO “does not recommend mass vaccination against monkeypox,” said Dr Tedros. In France, the High Authority for Health (HAS) recommends “vaccination of contact cases”, or ring vaccination. A strategy adopted “in 1972 during the human smallpox epidemic in Kosovo, which made it possible to put an end to it in a few weeks”, recalls Dr. Davido.

Reflexes to adopt to break the chains of transmission

Individually, as for Covid-19, reflexes are to be adopted to break the chains of transmission of monkeypox. “We know that the disease can be very contagious, as can chickenpox and human smallpox by causing infectious scabs,” explains Dr. Davido. So from the moment you have an eruptive disease, lesions on the body, you call 15 to be tested without delay and start tracing contact cases to vaccinate them. Then, the patients must isolate themselves until complete scabs, about three weeks.

And with cases that are characterized by sexual transmission, “it is important to do prevention, as we do for other sexually transmitted infections (STIs), insists the infectiologist. Then, if the cases explode and the stocks allow it, perhaps it will be appropriate to recommend the vaccination of populations at risk”. For the time being, “on all the elements to avoid the pandemic: we know the virus, it is the least transmissible, and we have a vaccine”, summarizes Dr Davido.

But without a strategy of reinforced surveillance and rapid action around each identified case, the scenario could turn to massive contagion, envisages a team of Dutch, Swiss, German and American researchers who carried out a study published in February in the journal Plos Neglected Tropical Deeases on all recovered monkeypox cases since this virus emerged and who believes it could be the next great pandemic. Why ? “The decline in population immunity linked to the discontinuation of smallpox vaccination has set the landscape for the resurgence of monkeypox,” the researchers point out. This is demonstrated by the increase in the number of cases and the median age of people who contract it. Moreover, the appearance of cases outside Africa highlights the risk of the disease spreading geographically, they warn. In light of the current pandemic threat environment, the public health significance of monkeypox cannot be underestimated.”

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