In 1980, surely one of the great achievements of modern medicine was celebrated – the eradication of smallpox. This infectious, highly contagious disease, including airborne, is characterized by fever, a characteristic vesiculopustular rash and often an evolution into sepsis frequently fatal (up to 30% of cases) caused the death of more than 300 million people in the last 100 years.
With a successful mass vaccination campaign, and taking advantage of the particularities of the virus, the last case of the dreaded disease was reported in 1977, leaving only samples of the virus in laboratories in the US and Russia. However, the specter of its eventual use as a bioterrorist weapon remains, which leads to the maintenance of vaccine stocks and the maintenance of research into new vaccines and antivirals for this disease.
However, smallpox is far from the only virus of the poxvirus group in existence, although it was surely by far the most virulent to the human species. This type of virus can infect a species electively, with high lethality (smallpox in humans, myxomatosis in rabbits, swinepox and goats) or behave more like generalists, with the possibility of infecting several species (vaccinia, monkeypox ).
One of the viruses of this group that has frequently caused infections in humans has been the monkeypox virus (monkeypox). It is a virus discovered in 1958 during an outbreak of a smallpox-like disease in captive monkeys (Von Magnus, Denmark).
The first case in humans was recorded in the 1970s and the virus seems to have benefited from the eradication of smallpox and the cessation of vaccination for this disease as it has evolved endemically in Africa where it has differentiated into two strains (Congo, with a lethality that is cited in 10% and West Africa, much less lethal).
In fact, the species barrier is largely immunological (we do not easily catch animal viruses because we have already come into contact with similar viruses spread in the human population before).
The eradication of smallpox thus opened the door to infections by animal poxviruses, albeit of incomparably less seriousness! Classically, monkeypox infection occurs on the African continent, often after close contact with animals (note that, contrary to what the name implies, the main hosts seem to be rodents/squirrels, rather than apes, although the latter may be severely affected, including with epidemic outbreaks).
More recently, in 2003, there was an outbreak in the US linked to prairie dogs kept at the distributor along with African rodents that were shown to be infected with this virus. The disease progresses with fever, an exanthema (rash) similar to chickenpox or smallpox, and marked enlargement of the lymph nodes – it is particularly severe in children and pregnant women.
The smallpox vaccine appears to be protective in up to 85% (note that given the rarity of these situations and the serious complications usual with this vaccine – the most classic of which is encephalitis in about 1-2 per vaccinated – it is not the benefit-risk balance was considered favorable, so it is not continued to be administered).
In the meantime, the available vaccine formulations have been improved, namely with non-replicative vaccines that may be better tolerated. There is currently an outbreak of this agent with cases all over the world, including our country (138 cases on 6/2/22).
The characteristics of this outbreak are highly atypical – it involves young male homosexuals or bisexuals, with genital and perianal lesions that suggest a local inoculation of the virus, the rate of complications being very low and lethality non-existent. In fact, the transmission of this virus seems to be much less efficient than that of smallpox – the usual routes being skin-to-skin contact or contact with contaminated objects (underwear or bedding, for example) – fomites – in which the virus can persist for a long time. weeks. There also appears to be a hitherto undescribed component of sexual transmission. Obviously, heterosexuals will not be immune, the biggest risk factor being the promiscuity of relationships, so it is important to warn without stigmatizing people, so that any case is quickly isolated.
Therefore, it is a situation to be monitored, without panic, without alarmism or false moralism that will be more harmful than useful.
Tiago Marques (Infectious Disease Doctor)
