how is it transmitted, what are the symptoms?

The French health authorities have identified, as of 21 July, 1,567 smallpox cases were on French territory, of which forty (3%) required hospitalization. All of these cases – with the exception of seven women and two children – are adult men, with an average age of 36 years.

The World Health Organization (WHO) has recorded more than 16,000 cases and five deaths in seventy-five countries and territories. WHO Director-General Tedros Adhanom Ghebreyesus declared a public health emergency of international concern (USPPI) against the disease on 23 July. The recent increase observed is unprecedented in the history of this tropical disease, generally confined to certain areas of the African continent.

Read too: Monkey pox: opening Tuesday of a large vaccination center in Ile-de-France and mobilization of “additional weapons”

What is monkeypox?

smallpox (varicella, in English) is an infectious and contagious disease caused by a virus of the genus orthopoxvirus, family to which vaccinia or smallpox belongs (declared eradicated in 1980 by the WHO after a large vaccination campaign). This virus is widespread among about twenty animal species, including certain primates and rodents, and has been transmitted to humans occasionally since the 1970s.

The disease is called “monkey pox” because it was discovered in 1958 in Denmark in crab-eating monkeys from Singapore and its symptomatology is very similar to human smallpox. However, it is far less virulent, contagious and deadly than this one.

Monkeypox is endemic in two tropical regions of sub-Saharan Africa, that is, it circulates more or less permanently in these two areas:

  • the Congo Basin, mainly in the Democratic Republic of Congo;
  • West Africa, mainly in Nigeria.

Unlike RNA viruses like SARS-CoV-2, the monkeypox virus is double-stranded DNA, meaning it replicates when it enters the nucleus of infected cells. It is quite large, oval in shape and protected by two membranes. Its genome is also quite long, which makes genomic analysis difficult.

DNA viruses undergo fewer mutations than RNA viruses. However, there are two variants (or “clades”) in the areas where it naturally circulates: the West African clade and the Congo Basin clade.

A comparison of the genomes of these two clades carried out in 2005 by a North American team concluded with a difference of approximately 0.55%, which is enough to give them a different virulence and mortality.

What are the symptoms of monkeypox?

Like all viruses of the orthopoxvirus genus, the monkeypox virus causes pustular disease. After an incubation period of five to twenty-one days during which the infected person is not contagious, the disease is first manifested by a high fever that lasts about one to three days, great tiredness, headaches and aches and pains. on body. “The disease usually heals spontaneously, after two to three weeks, but sometimes four weeks,” specifies the Public Health of France (SPF). The vast majority also have pronounced swelling of the lymph nodes in certain locations (under the jaw, in the neck, and in the groin).

After two days, it enters its “eruptive” and contagious phase with the appearance of lesions on the skin, in the form of pimples that present four successive forms:

  1. flat, red spots (one to two days);
  2. papules, solid and raised (one to two days);
  3. blisters, containing a clear liquid (one to two days);
  4. pustules, with a purulent liquid (five to seven days), containing large amounts of live virus, which can cause contamination by contact if the pustules are pulled out.

The number of pimples varies according to the individual, itching may occur, but they all evolve at the same time in a period of two to four weeks for drying, which leads to the formation of a crust, until complete disappearance. However, they can leave visible traces on the skin for some time.

In Africa, these pimples are concentrated on the face and extremities (palms of the hands, soles of the feet, genitals) and, to a lesser extent, on the trunk. In Europe, skin lesions tend to be concentrated on the face and the genital and perianal areas, but they can also appear on the palms of the hands and soles of the feet.

This poses a problem: symptoms are less obvious and diagnosis is more difficult. This clinical picture is confirmed by Benjamin Davido, an infectious disease specialist at the Raymond-Poincaré hospital in Garches (Hauts-de-Seine): “This virus behaves like a great mimic of herpes or syphilis. Therefore, it is easy to miss the diagnosis. »

Read too: Monkeypox: A study of over 500 cases reports more varied symptoms than expected

Is smallpox dangerous?

Some cases may have more serious symptoms, such as infection of the dermis, lungs (pneumonia), brain (encephalitis), cornea (with loss of vision) or, more rarely, sepsis (organ dysfunction secondary to a serious infection). “The disease is more severe in children and in immunocompromised people. It can be complicated by a superinfection of the skin lesions or by respiratory, digestive, ophthalmological or neurological disorders., says SPF. As of July 21, no monkeypox-related deaths have been recorded in Europe, according to the SPF.

In endemic areas, these complications primarily affect frail individuals – young children, the very elderly, people who are immunocompromised, or those affected by a disease that overwhelms the immune system (certain cancers or blood disorders, for example).

In Africa, the death rate ranged between 3.6% and 10.6%, according to a review published by a team of American researchers in February 2022. Between 1970 and 2019, monkeypox caused the deaths of 78 people, including 68 related to the Congo Basin clade. And since the beginning of 2022, health authorities have recorded an additional 66 deaths, out of 1,408 cases (from 1er June), including 58 deaths in the Democratic Republic of Congo (DRC) alone.

In Europe, with the disease only being reported in 2018, it is currently not possible to know the precise number of deaths there. Differences in health systems across continents may explain differences in virulence. The WHO notes that“with proper care, most patients recover”. However, it will take time and genomic analyzes of the virus to find out more.

Read the decryption: Article reserved for our subscribers Chickenpox: African countries call for equitable access to vaccine

How is the disease transmitted?

Transmission from animals to humans can occur through direct contact with the blood, body fluids, mucous membranes or skin of an infected animal, or through the consumption of undercooked meat. Human-to-human transmissions are also possible, but less observed by researchers. It is well established that the pathogen is transmitted by contact with skin lesions or respiratory secretions (the splashes emitted when speaking), but probably after prolonged face-to-face interaction.

Viruses of the orthopoxvirus genus survive a long time outside the human body and can be transmitted through surfaces. Therefore, it is risky to eat or drink from the same dishes or sleep in the same room as a sick person.

According to the SPF, most people with smallpox in France are men who have sex with men and, for many, with “multiple sexual partners”. “Anyone who has close physical contact with another person who has contracted smallpox is at risk, regardless of sexual orientation,” he said. explained to World Yannick Simonin, a professor specializing in emerging viruses at the University of Montpellier, who asks “be careful not to stigmatize the homosexual community”.

Is Monkeypox a sexually transmitted infection? Contamination is most likely explained by close and prolonged contact that involves sexual intercourse, according to Mr. Simonin:

“Although monkeypox is not currently considered a sexually transmitted disease, close contact during sexual intercourse is an important risk factor for disease transmission. »

But sequencing the genome of the virus, six times longer than that of SARS-CoV-2, should make it possible to confirm an evolution of the modes of transmission, as indicated in this article published in the journal Nature.

Read too: Monkey pox: why are gay and bisexual men more affected?

Does the smallpox vaccine protect against the disease?

Orthopoxviruses have surface proteins and therefore “signatures” very close together. They are quite sensitive to antibodies developed against other viruses of the same family; say they generate cross-immunity. The virus can thus be fought with existing vaccines against other viruses of the same genus.

The vaccine against vaccinia, a disease commonly known as “cowpox”, used worldwide in the 1960s and 1970s to eradicate smallpox, is 85% effective in combating monkeypox virus infection. In France, this vaccination against smallpox was mandatory until 1979, which means that the 34 million people over 43 years of age (that is, half of the population) are, in principle, well protected against smallpox. “Even people who were vaccinated many decades ago maintain very, very high levels of antibodies and the ability to neutralize the virus.”assures Luigi Ferrucci, scientific director of the National Institute on Aging, in Baltimore (Maryland), in New York Times. Works published in 2007 in the New England Journal of Medicine showed that the amount of antibodies against smallpox decreased very slowly. This protective effect is observed in patient data: unvaccinated people account for between 79% and 96% of cases.

Currently, it is not planned to vaccinate the entire population: current stocks are limited and do not allow large-scale vaccination, the last case of human smallpox dates from 1977. But in view of the progression of the epidemic, the government announced, on 8 July, the extension of vaccination against smallpox to the most exposed groups, especially homosexual men, after the opinion of the High Health Authority (HAS). A decision deemed insufficient by several associations, such as Inter-LGBT, which criticized “lack of preparation” government and difficulties in accessing vaccination.

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