First identified in 1970 in rural villages in the rainforest areas of Central and West Africa, when smallpox was in the final stages of eradication, monkeypox virus (mpox, formerly called monkeypox) continues to mutate. A very aggressive strain of the pathogen, the Clade I varianthas in fact acquired a high capacity to be transmitted from man to man through sexual intercourse. Until now Clade I had remained (almost) silent – explains the Mario Negri Irccs Institute for Pharmacological Research on its website – causing only small outbreaks in Central Africa and, before last year, no sexually transmitted infections had been reported.
Since late 2023, Nature reports, an atypical outbreak has been identified in a conflict-torn region of the Democratic Republic of Congo. According to one of the latest reports made public, there are about 240 suspected infections and 108 confirmed ones. But the real number is probably much higher, because the country does not have the facilities for tracking and systematic analysis to accurately estimate the current spread of the virus. This cluster of infections worries researchers because almost 30% of those infected have been sexually transmitted, suggesting that the virus has adapted to be transmitted more easily through this transmission route. This could lead to a very rapid spread across the border “also because – stressed Nicaise Ndembi, virologist at the African Centers for Disease Control and Prevention – the Democratic Republic of Congo is surrounded by 9 other countries”.
What happened in 2022
The concern – the Mario Negri Institute points out – arises because as early as May 13, 2022, there had been an epidemic of monkeypox in non-endemic countries, with many outbreaks observed in Europe and the United States. In that case, it was a strain of mpox called Clade II that presumably originated from a strain circulating in West Africa and which is believed to have triggered the global epidemic. Unlike the previous variant, the new Clade I strain has a much higher mortality rate – about 10% of infected people do not survive the infection – and is therefore more lethal.
Monkeypox is endemic – that is, permanently present in the population – in the tropical rainforest states of Central and West Africa: Benin, Cameroon, Central African Republic, Democratic Republic of the Congo, Gabon, Ghana, Côte d’Ivoire, Liberia, Nigeria, Republic of the Congo, Sierra Leone, and South Sudan.
How it is transmitted
Human-to-human transmission – as stated on the website of the Istituto Superiore di Sanità (ISS) – through close physical contact, including sexual activity, is a significant factor in the current epidemic. Mpox can be transmitted to anyone who has close contact with an infected person, regardless of sexual orientation or gender identity. However, in the ongoing epidemic since May 2022, most cases have been observed among men who have sex with men (MSM: men who have sex with men) and who reported recent sexual intercourse with one or more partners. Other transmission routes have also been documented, such as through the placenta, from mother to fetus (which can lead to congenital Mpox) or during and after birth through direct skin-to-skin contact between mother and newborn.
It is not yet clear whether MPXV can also be transmitted from person to person through blood, semen or other bodily fluids during sexual intercourse. However, several studies have detected viral DNA in the semen of infected individuals for weeks after acquiring the infection. The UK Health Security Agency and other international agencies recommend that people who have recovered from MPXV infection continue to use condoms for at least eight weeks after infection as a precaution.
Symptoms and how to treat it
An infected person – as stated on the ISS website – remains contagious for the entire duration of the symptomatic disease (from the appearance of prodromal symptoms until the crusts of all lesions fall off and new skin forms), normally 2 to 4 weeks. It is not known whether the virus can be spread by asymptomatic people.
The patient may be advised to take painkillers or antipyretics to relieve the symptoms of the infection, which can be more severe and lethal, especially in particularly vulnerable population groups such as children, pregnant women, and immunocompromised individuals. Complications of monkeypox may include: fever, severe headache (generalized or frontal), lymphadenopathy (swollen lymph nodes), back pain, myalgia, and severe asthenia (weakness), vesicles, pustules, and small crusts that appear, especially on the face, and then fall off.
Differential diagnosis includes other rash diseases, such as chickenpox, bacterial skin infections, scabies, syphilis, and drug-related allergies. Lymphadenopathy during the prodromal phase of the disease may be a clinical feature to distinguish Mpox from chickenpox or smallpox. When faced with a suspected case of Mpox, it is necessary to collect biological samples from the skin lesions and transport them safely to a reference laboratory.
The vaccine
The human smallpox (Variola) vaccine has been shown to provide protection against monkeypox. In Italy, mandatory vaccination against smallpox was interrupted in 1977 and repealed in 1981 because vaccination allowed the disease to be eradicated worldwide. Starting in 2022, vaccination was reintroduced exclusively for a series of risk categories. As stated in a circular from the Ministry of Health dated August 8, 2022, the people who can benefit from vaccination are: people who have had unprotected contact with an infected person, people exposed to the virus in a professional context such as medical and laboratory personnel, gay, transgender, bisexual people and other men who have sex with men with specific risk criteria. Vaccination is therefore not intended for the general population.
Vaccination – the Mario Negri Institute emphasizes – allows to prevent serious forms of the disease, lethal complications, but it is not yet known whether it is able to prevent contagion. It is also not yet clear whether this vaccine can also be effective against the Clade I strain, but so far the data from ongoing studies are promising.
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