Chickenpox: “has nothing to do with smallpox”

A first case of monkeypox was detected in France. The first case was reported in the UK on May 6, 2022, before spreading to Spain, Portugal, Canada, the US, Sweden and Italy. The European Center for Disease Prevention and Control (ECDC) says “follow the situation closely“and recommend”isolate and test suspected cases and report them promptly.” science and future takes stock with Antoine Gessain, physician and researcher, who directs the Epidemiology and Pathophysiology of Oncogenic Viruses unit at the Institut Pasteur. He specialized in interspecies transmissions (zoonoses), in particular of African origin. The Institut Pasteur has been working on monkeypox for several years with the Institut Pasteur in Bangui, Central African Republic.

Sciences et Avenir: Which pathogen is responsible for monkeypox?

Antonio Gessain: It is a DNA virus, therefore stable from a genetic point of view, nothing like an RNA virus like SARS-CoV-2 (responsible for Covid-19, editor’s note) or HIV. It’s a virus”smallpox“(“smallpox” in English, editor’s note). These are very large viruses, of which we should not fear the emergence of variants.

Which animals are carriers of this virus?

The reservoirs of monkeypox are poorly understood. It’s probably rodents, squirrels, even if the disease is called “varicella“. There are two variants of the virus, but not in the sense of the omicron variant of Covid-19, for example. They are simply two different versions of the virus: one in West Africa, mainly present in Nigeria, and the other in Central Africa, especially in the Democratic Republic. Congo (DRC) and the Central African Republic.

What is the relationship between monkeypox and classical smallpox as we know it?

Monkeypox has nothing to do with smallpox. The latter is an extremely serious viral disease that has decimated part of the human population for centuries. Its elimination was the greatest achievement of the World Health Organization (WHO) in the 1970s, with an active and targeted search for cases, as well as the widespread vaccination of the world population. Adults over 40 often still have a very distinctive mark on their arm.

What signs have been seen in infected people?

The person becomes infected and first goes through an incubation phase that lasts between 5 and 20 days. Then comes a phase with fever, inflamed lymph nodes, cough, then skin lesions appear. They resemble what can be seen in cases of chickenpox or smallpox: vesicular-papular lesions, which form a bulge with serum inside (an organic fluid, editor’s note). They dry little by little before they become crusts, like chickenpox. In most cases, people recover without any serious illness. There is currently no effective therapy. Deaths occur only in rare cases. The mortality rate is estimated at 1% for the West African strain and 5 to 10% for the other. But patients die because they are children, sometimes malnourished, have bacterial superinfections due to skin lesions. Patients often have comorbidities and the healthcare system is not comparable to ours.

How is this disease transmitted?

Mainly by pulmonary droplets, which implies a very close contact. They are not aerosols or microparticles that travel far away. Monkeypox is also transmitted by close contact through skin lesions, much like chickenpox. We tend to scratch the blisters, which makes skin contact quick to contamination. There is also the risk of environmental contamination. Places that patients have contaminated with biological fluids, such as a hospital bed or nosocomial transmissions, when healthcare personnel are not wearing gloves. Sexual transmission is poorly understood, poorly studied and poorly documented. There are no large-scale studies in the context of these epidemics. They are often retrospective and performed on small cohorts of patients.

When did monkeypox appear?

It is a virus unknown before 1958. That year, an epidemic begins in a pet shop with monkeys in Copenhagen, Denmark, with skin lesions that look like smallpox. Smallpox, the “varicella“, was then isolated and named that way, even though the monkey is not the initial reservoir of the virus. The first human case was recorded in 1970 in a child in the Democratic Republic of Congo (DRC). Small non-negligible epidemics occurred regularly until 2017 An epidemic then broke out in Nigeria, with hundreds of cases, strains of West African origin and death. of reservoir transport. In 2013, rats from the Gambia and squirrels from Ghana were sold in small pet stores in the US. In contact with other animals, they infected prairie dogs, very popular with children, 72 of them were sick. no serious hospitalizations and no cases of human-to-human transmission had been censored.

How did the virus manage to spread in several countries this time?

On May 6, 2022, a person traveled from Nigeria to England, resulting in around 20 cases. People infected in Portugal, Spain and Italy are likely to be of the same strain in Nigeria. The virus would have spread within the homosexual community before spreading across Europe. It would really be very unlikely that there were several departures from Africa at the same time, by different people. There’s probably low-noise scattering out there, and what we’re seeing right now is probably just the tip of the iceberg.

Smallpox is no longer a mandatory vaccine. Would it be useful to vaccinate the population?

There is a form of cross-immunity between vaccination against smallpox and protection against smallpox. But currently, vaccination is not justified. The arrival of this virus in some immunocompromised and seropositive people can lead to more severe forms. In the past, people were vaccinated, which protected them from 85% of the virus. We no longer vaccinate and people under 40 are a potential risk population, especially in countries in conflict, where war and difficult living conditions make contact with rodents more frequent. In France, vaccination would not make sense at the moment.

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