What is smallpox, the first infectious disease officially eradicated

What is smallpox

It is the first and only infectious disease to have been officially eradicated, but now it is back in the headlines: we are talking about smallpox. In recent days, in fact, some cases of monkeypox, an infectious disease usually widespread in Africa caused by a virus that belongs to the same genus as human smallpox, have been detected in the United Kingdom and in Europe (with a confirmed case in Italy). and which manifests itself with similar symptoms. Infrequent among humans, transmission can occur by direct contact, through exposure to droplets of saliva or through sexual intercourse. Anyone who has received the vaccination for human smallpox (in Italy repealed since 1981) also seems to be protected for this disease.

Human and monkey smallpox, similarities and differences Let's take a step back. Smallpox is an infectious disease caused by the Variola virus, a member of the O rthopoxvirus family, which also includes other viruses capable of infecting both humans and animals, such as the cowpox virus (Cowpox virus). vaccine (Vaccinia virus) and also monkeypox (Monkeypox virus). Similarly to other viruses of the same genus, the contagion of human smallpox occurred with direct contact between people, through body fluids (for example saliva or nasal excretions) or contaminated objects. The incubation period of the disease ranged from 7 to 17 days, with the first symptoms manifesting as fever, malaise, headache, body aches and vomiting.

After this first phase, usually lasting a couple of days, the typical skin manifestations of the disease began to appear: initially red spots (period in which the patients were more contagious) which then became real pustules, which later evolved into scabs, which eventually, with healing, detached from the skin, which however remained marked by deep scars. The clinical manifestations of human smallpox resemble that of monkeys, which however - as stated on the dedicated page of the World Health Organization (WHO) - is less contagious and causes a less serious disease (mortality is estimated at 3-6 %). Human smallpox, on the other hand, was fatal in 30% of cases: according to the WHO, it was one of the most devastating diseases known to humanity, causing millions of deaths before being declared definitively eradicated in 1980.

A brief history of smallpox eradication In fact, the history of smallpox eradication began much earlier, in 1796, when the English doctor Edward Jenner developed the first vaccine, aimed precisely against this disease. Jenner had observed that milkmakers, who often fell ill with cowpox, were affected less by the human disease. For this he developed a serum from cowpox pustules, inoculated it to an eight-year-old boy who then infected with human smallpox. Surprisingly, the child did not fall ill with smallpox: the immunization had actually taken place.

After almost two centuries, in 1967, the WHO launched an immunization and surveillance plan aimed at definitively eradicating this disease: initially with mass vaccination campaigns to obtain at least 80% vaccination coverage in each country of the world, and then through containment strategies, which consisted in identifying isolated cases and vaccinating all possible contacts to isolate the epidemic from the rest of the population. Thanks to these efforts, the last natural case of human smallpox was detected in Somalia in 1977. After three years, WHO has finally officially declared the eradication of the disease.

The smallpox vaccine and its scar Since Edward Jenner, the principle behind the smallpox vaccine hasn't changed that much: it contains still a live virus of bovine origin (the Vaccinia virus) which is able to confer protection against the human vaccine in 95% of vaccinated people, even in contact with a sick person. The inoculation of the vaccine takes place under the skin and, since several doses of live virus are administered, it causes a small excoriation on the site where it is injected: in the days following the vaccination, a small red and irritated wound forms that will become a blister and then a scab, leaving, once it fell, the typical scar of those who underwent this vaccination.

As cases diminished and disappeared, vaccination against smallpox was suspended in all Western countries: in Italy the obligation was removed in 1981. Those born before that date could now also be protected against monkeypox, which, being very similar to humans, is susceptible to the smallpox vaccine. At the moment, despite not being administered for more than 40 years, Italy has a stock - for emergency situations - of 5 million doses of smallpox vaccine which, with dilutions, can reach 25 million doses.

As the ISS concludes, however, given the complications that this vaccine can cause, "the Ministry of Health advises against vaccination extended to the population in the absence of imminent danger".