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Agriculture brings humans and animals closer together: This also increases the risk of disease being transmitted
Photo: Lucas Ninno / Getty Images
The force and extent of the corona pandemic surprised most people.
It was only through Sars-CoV-2 that it became clear to many of the dangers posed by viruses that originate from the animal kingdom: According to WHO studies, the coronavirus first developed in bats before it later spread to humans via a previously unknown animal.
Many pathogens that plague humans have their origin in animal organisms.
HIV, Ebola and Sars are well-known examples of such so-called zoonoses.
In order to better assess and recognize the danger posed by them, US scientists have developed a freely accessible database that classifies the risk of transmission.
The list published in the "Proceedings" of the US National Academy of Sciences ("PNAS") is intended to help prioritize such pathogens for further research and monitoring.
The transfer of such pathogens from animals to humans is known as spillover; to date, more than 250 zoonotic pathogens are known.
However, it is estimated that hundreds of thousands of animal viruses have the potential to spread to humans.
Faced with this threat, researchers at the University of California at Davis, based on an analysis of studies and a survey of international experts, identified factors that describe the risk of spillover of such viruses.
This includes, for example, how often and how many different animal species a pathogen can attack, how far these hosts are geographically distributed and how close their contact to humans is.
Other factors include the genetic structure of the pathogen and how it is transmitted.
These 31 risk factors in total form the framework for the spillover database, which the scientists fed information on 887 wild animal viruses.
The first twelve places on this list occupy pathogens that have already jumped over to humans: The Lassa virus takes first place, followed by Sars-CoV-2, Ebola, Seoul and Nipah virus keep.
Lassa fever, which is usually mild, first appeared in Africa at the end of the 1960s.
The virus' natural host is a species of mouse.
In the case of the Seoul virus, which is mainly spread in Asia and often leads to severe disease, it is the brown rat.
The Nipah virus, which often causes fatal encephalitis, can be traced back to fruit bats.
Corona virus continues to be at high risk
The authors justify the fact that Sars-CoV-2 only ranks second with the fact that the list assesses the potential for further spillover in the future.
Whether this will happen is speculative.
In addition, important information about Sars-CoV-2 is still unknown.
However, more is known about other viruses that have been researched for a long time - such as data on the number and range of host species.
In order to be able to better assess the risk for the future development of the virus, it would be helpful, for example, if it were known via which intermediate host the virus was transmitted from bats to humans - this scenario is currently considered to be the most likely.
Pangolins, for example, are suspected, but details are not yet known.
In general, the researchers estimate the risk of spillover from various coronaviruses to be very high: the top 20 on the list alone contain five coronaviruses that have not yet spread to humans.
Overall, around a third of the 50 viruses with the highest risk of transmission are coronaviruses.
"Sars-CoV-2 is just one example of many thousands of viruses that have the potential to jump from animals to humans," first author Zoë Grange is quoted in a communication from her university.
"We not only need to identify viral threats with the greatest risk of spillover, we also need to prioritize them before another devastating pandemic occurs."
The interactive list can be adapted by each user, for example by selecting a country or a virus family that they are particularly interested in.
Above all, however, the “SpillOver” project is a continuously updated list: Scientists can contribute data on viruses, assess the risk of new pathogens and thus improve the database over time and make it more precise.
Cooperation in real time
“The database is supposed to start a global discussion.
We are also hoping for real-time scientific collaboration in order to identify new threats at an early stage, ”explains study director Jonna Mazet.
»SpillOver can help improve our understanding of viral threats.
Hopefully it will enable us to act to reduce the risk of transmission to humans before a pandemic breaks out. "
joe / dpa
