More than 400,000 people are infected with a SARS-CoV-2-type coronavirus each year

Some 500 million people in Southeast Asia are at risk from bats carrying the coronavirus. Interactions that present a high risk of transmission, even if most of them are benign and go unnoticed.

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If no one has confirmed yet the origin of SARS-Cov-2, it is almost certain that the virus comes from an animal reservoir, and more likely from a bat. Over the past twenty years, several viruses from bats have thus “jumped” from animals to humans, causing epidemics, such as SRAS, MERS, and of course, Covid19. Events, all in all, relatively rare. Unless…

According to a new pre-published study on the server MedXriv, around 400,000 people are thought to be infected each year with a coronavirus SARS-CoV type. And we are talking here about direct transmission and not all the cases of human-to-human transmission that may possibly occur afterwards. In short, it’s a bit like having 400,000 ” zero patients Of SARS-CoV-2 each year.

Each infection represents a potential risk for the virus to adapt to humans

Except, of course, most of these coronaviruses cause no symptoms or only mild symptoms, so these infections go completely unnoticed. Either they are poorly adapted to humans, or they are immediately destroyed by the immune systemor they remain confined to small communities. Nevertheless, each of the 400,000 infections represents the risk that the virus will adapt to its host and lead to an epidemic, the researchers warn. ” There are certainly also a large number of diseases linked to these coronaviruses and for which the cause is not identified. “, Says Peter Daszak, lead author of the study.

A statistical and epidemiological model

Among the bats, 23 cash are known to be coronavirus carriers SARS type susceptible to pass to humans. Most of these bats live in Asia – which is why the majority of epidemics originate in this region – especially in southern China, Laos, Vietnam and Indonesia, which are densely populated areas. . Peter Daszak and his alliance colleagues EcoHealth and some Duke-NUS Medical School of Singapore created a detailed map of the 23 species and found that 500 million people were exposed to these bats.

They then used an epidemiological and statistical model to assess the frequency of zoonoses related to these bats. For example, they relied on a previous study involving 218 people and showing that at least 3% of them had tested positive for coronavirus antibodies transmitted by bats. The researchers took into account various parameters, such as the number of bat species likely to harbor SARS-like viruses, the ability of these viruses to infect humans, the duration and frequency of contact, or degree of immunity of exposed populations.

The best way to prevent epidemics is to control the initial passage from animals to humans

This study is not the first to show the strong presence of SARS-type coronaviruses in bats. In February, scientists had identified two variants close to SARS-CoV-2 circulating in Cambodia more than 10 years ago. In 2020, six unknown coronaviruses had been identified in bats in Burma. Coronaviruses are not the only ones, however animal viruses to threaten humans.

The Ebola virus, for example, is a filovirus while the Lassa virus is an arenavirus (the main reservoir of the latter is a small rodent called Mastomys natalensis). But, in the context of the Covid-19, our attention should be particularly focused on SARS-Cov viruses, say the authors of the study. ” The best way to prevent epidemics and the pandemics is to control the initial passage from animals to humans and to monitor the start of the spread of epidemics before they get out of hand “. As can be seen from the maps, the work is clearly on the Asian side.

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