What is monkey pox localized outbreaks have regularly occurred in recent years in Central and West Africa. These emergences were studied and monitored until the global emergence of the disease, observed in May 2022.
In the early 1980s, following the global eradication of human smallpox, smallpox vaccination was stopped. The people vaccinated are protected by an estimated 80% of the monkey pox virus, as there is cross-immunity between the Mpox virus and the human smallpox virus.
In July 2022, the World Health Organization (WHO) declared that the spousal monkey pox smallpox epidemic is a global health emergency, following its “extraordinary” spread in more than 75 non-endemic countries (regions where the disease does not exist continuously).
Understanding the Monkey Pox Virus: Origins and Classification
The Mpox virus is a double-stranded DNA virus (about 200 kilobases), Poxvirid family and the genus Orthopoxvirus. It is related to the virus responsible for human monkey pox, a disease eradicated by vaccination in 1977.
The monkey pox virus was first isolated in 1958, in a monkey colony in Copenhagen, Denmark. These monkeys had skin lesions that evoked human smallpox. Hence the name of smallpox of the monkey, attributed to this disease.
Although it is still commonly referred to as smallpox (monkey), it is not via monkeys that this disease is transmitted to humans, but from rodents (see below in the paragraph “Transmission”). Since the end of 2022, the WHO has favoured the name “Monkey Pox”.
There are two main types of monkey pox virus:
- Clade 1, present in the Congo Basin in Central Africa;
- And clade 2 in West Africa.
The virus currently circulating in Europe comes from clade 2, which is involved in Nigeria’s epidemic.
Read more about the nomenclature of variants of this virus (WHO site)
How is the disease transmitted?
Mpox/monkey pox smallpox is a zoonosis, i.e. a disease transmitted from the animal to humans.
Monkey pox is transmitted to humans from rodents (e.g. in Africa, forest squirrels or Gambian rats). However, the animal reservoir has not yet been formally identified. According to a study published in 2021 by the Pasteur Institute, concerning the smallpox of monkeys in the Central African Republic, the genomic history suggests multiple introductions from forest animal reservoirs.
The human transmission of the monkey pox virus is:
- Either by direct contact with infected animals,
- Either by contact with skin lesions or biological fluids,
- Or indirectly via contaminated materials (such as bedding or surfaces).
- It could also be done via the respiratory droplets of an infected person.
From May 2022, thousands of cases of monkey pox were recorded in non-endemic countries (the region where the disease does not exist permanently). Studies are under way to better understand epidemiology, sources of infection and modes of transmission of this disease. As of 1 September 2022, there were several tens of thousands of cases diagnosed.
Rapid identification of new cases and monitoring are essential to reduce the risk of human-to-human transmission.
What are the symptoms?
The clinical presentation of Mpox/monkey pox smallpox is an attenuated form of human smallpox, an orthopoxvirus infection related to human smallpox, which globally eradicated globally was declared in 1980.
However, Mpox is less contagious than human smallpox and causes a more benign disease.
Historically, in Africa, the monkey pox manifests itself as follows:
- An average incubation period of 12 days before the onset of the first symptoms;
- Usually febrile syndrome (curve, headache, fatigue, etc.), for 1 to 4 days; the subject is contagious as soon as the first symptoms appear (see DGS card for healthcare professionals);
- Then an eruptive phase, for 2 to 4 weeks, with skin rashes in the form of small spots (mapopulaular rashes evolving to pustules and crusts), which mainly reach the palms of the hands and soles of the feet, with swelling of the lymph nodes.
The epidemic that has been raging since May 2022 in Europe – and spread to the rest of the world – shows more localized skin rashes, often on genital or perianal areas (see MPXV record of Public Health France).
Symptoms last 2 to 4 weeks and the disease generally recovers spontaneously. Complications may occur such as skinborne infections, sepsis, encephalitis, or corneal disorders. They can lead to serious forms of the disease. The WHO reports on its site a fatality rate of about 3 to 6% in 2022 for epidemics in Africa, with lethality being higher with the Central African strain and in an endemic context. In the context of the global epidemic in 2022, the lethality is about 0.03%.
How to diagnose the infection
The diagnosis of Mpox/monkey pox smallpox is first carried out clinically by specialist doctors (infectiologists, dermatologists). It is then confirmed in the laboratory by real-time PCR on oropharyngeal swab and on pustule swab.
Diagnosis of monkey smallpox should take into account other eruptive diseases: in particular chickenpox, but also measles, bacterial skin infections, syphilis, herpes, etc.
What are the treatments?
An antiviral agent, originally designed for the treatment of smallpox, has recently been approved for the treatment of monkey smallpox. This treatment is only indicated in the severe forms of the disease, and should be administered as early as possible for an oral period of 15 days.
The High Health Authority (HAS) offers on its website quick responses to healthcare professionals regarding Monkeypox infection and primary medicine management.
How to prevent the disease?
In endemic areas (in Africa), the main strategy for preventing Mpox/monkey pox is to limit human/wildlife interfaces, thus raising awareness and informing populations of risk factors for zoonotic transmission (by animals) and thus reducing the risks of transmission from the animal to humans. Beyond that, we must act on reducing factors that also contribute to the emergence of epidemics such as poverty, through dependence on bushmeat as a protein source and density and promiscuity in homes, or military conflicts that lead to population displacements.
More generally, in order to limit human-to-human transmission, the prevention strategy is based on information and awareness-raising:
- Raising awareness of the risk factors of transmission: avoiding skin contact with sick people or contaminated equipment (see above),
- Informing at-risk populations and healthcare professionals.
The development of rapid diagnostic tests will improve diagnosis and prevent human transmission.
Smallpox vaccines, used in the smallpox eradication programme in the 1970s, offer cross-protection against monkey pox. Other more recent vaccines have also been developed, one of which has been approved for the prevention of Mpox.
Some countries offer a vaccine to people at risk, such as laboratory staff, health workers, etc. In France, the High Health Authority recommended in its opinion of 7 July 2022 that preventive vaccination be offered to those most vulnerable, namely men who have sex with men, owners of places of sexual consumption and sex workers.
Who is affected?
Mpox/monkey pox smallpox is an emerging infectious disease, first identified in humans in 1970 in the Democratic Republic of Congo (DRC). Second, most cases were reported in rural and tropical rainforest areas in Central and West Africa.
The frequency of outbreaks, and their sizes in human populations, have steadily increased in recent years. The geographical spread of the monkey pox has spread beyond Central African forests, to savannah or urban areas to other parts of the world where cases have been imported.
This pattern of transmission is partly explained by the worldwide decline of post-smallpox vaccine immunity following the discontinuation of this vaccination in the 1980s (see retrospective analysis by the Pasteur Institute in July 2020).
However, other factors are involved, which have been prone to change over the past 30 years: major changes in land use, massive deforestation, increasing urbanization, destruction of wildlife habitat, and loss of biodiversity. These pressures on ecosystems due to human activity lead to an increase in the human/wild fauna interfaces, as well as the modification of the structures and dynamics of animal communities.
In addition, socio-economic instabilities and civil wars increase the human/wildlife interfaces, increasing the risk of virus passages from animals to humans.
Thousands of human cases of monkey smallpox are reported annually in several West African countries (including Nigeria) and Central Africa. In the Congo Basin, two countries are particularly affected, the Democratic Republic of the Congo (DRC) and the Central African Republic (CAR), for which an increase in the number of epidemics has been observed over the past two decades.
Since 2018, human cases have been exported, mainly from Nigeria, to non-endemic countries: the United Kingdom, Israel, Singapore and the United States, without giving rise to local clusters/homes of human-to-human transmission.
Since the beginning of May 2022, a global epidemic has come to the fore as many non-country endemic cases and the declaration of a “public health emergency of international concern” by the WHO on 23 July 2022.
These cases are not the result of travel in endemic areas.
Since 6 July 2022, the WHO has published a weekly epidemiological report twice a week.
Between 1 January 2022 and 19 June 2023, 87972 cases and 147 deaths were recorded worldwide.
See the WHO disease sheet