The SARS-CoV-2 coronavirus has not been the only one mortal virus that has emerged throughout the history of mankind. Multiple other viruses lethal to humans appeared and disappeared without a trace, while scientists try to unravel the causes that lead these viruses to the end of their existence.

He severe acute respiratory syndrome (SARS) was notified for the first time in February 2003, recalls in an article the BBC, when the WHO office in Beijing received a notice about “a strange contagious disease“which had caused the death of 100 people in just one week.

The Chinese province of Guangdong was the origin of the SARS virus: its local markets, full of exotic species where restaurants coexisted a few meters from places where these animals were gutted were the perfect breeding ground for the spread of this virus.

At that time, health authorities feared that this virus could cause a global pandemic like the one in 1918. However, two years after its detection and after infecting more than 8,000 people worldwide, SARS abruptly disappeared. According to epidemiologist Sarah Cobey of the University of Chicago, the sophisticated contact tracing and the peculiarities of the virus – it was easier to identify those infected because there were no asymptomatic patients – were key in making it disappear.

Besides SARS, other two viruses have been extinguished: the smallpox and rinderpest. In both cases, vaccines were key to winning the battle against the spread of these viruses. However, Stanley Perlman, a microbiologist at the University of Iowa, argues that it is generally “very difficult” for these to go away “when you have a virus that is well adapted“.

“SARS left because there is no other obvious host“Perlman says. That virus jumped to humans through a palm civet, a mammal considered a delicacy in China. According to Perlman, the species that transmitted the virus to a human was likely one of the few that was directly infected from a bat.

In the case of the flu, there are two main types: A and B. The former infects many animals in addition to humans, while the latter only infects humans. However, not a trace remains of the strain that caused the 1918 flu pandemic, and not the one that caused the 1957 bird flu outbreak, with 116,000 in the US, recalls the BBC.

Epidemiologist Sarah Cobey notes the following: “If you focus on a particular strain, or rather, any particular genetic sequence that is replicating itself, there is a very, very high extinction rate“According to Cobey,” the strains are disappearing every two years. It is complicated, but we are seeing a very high turnover. “

However, some scientists point out that “the extinct term is misleadingAccording to Ian Lipkin, an epidemiologist at Columbia University, “viruses can be present in many places; They can lurk in people, they can lurk in materials that are stored in freezers, they can lurk in wildlife and domestic animals; it is really impossible to tell if a virus is extinct. “

For his part, Cobey indicates that “there are many pathogens out there, most people do not know how many “, hence the Covid-19 pandemic can serve to” reflect on what types of diseases we want to eradicate. “