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Which animal viruses will cause future pandemics?

Although viruses spill over from animals to humans quite often – as it most likely happened with SARS-CoV-2 three years ago – scientists still have a rather rudimentary knowledge of most animal viruses. Unfortunately, knowing the list of nucleotides that compose a virus’s genomic sequence offers very few hints about its possible ability to infect humans.

According to a new perspective article published in the journal Science, instead of letting the next pandemic take us once more by surprise, the scientific community should invest in research aiming to proactively identify viruses which might infect humans.

“A lot of financial investment has gone into sequencing viruses in nature and thinking that from sequence alone we’ll be able to predict the next pandemic virus. And I think that’s just a fallacy,” said co-lead author Cody Warren, an assistant professor of Veterinary Biosciences at the Ohio State University.

“Experimental studies of animal viruses are going to be invaluable. By measuring properties in them that are consistent with human infection, we can better identify those viruses that pose the greatest risk for zoonosis and then study them further. I think that’s a realistic way of looking at things that should also be considered.”

According to Warren and his co-author Sara Sawyer – a professor of Molecular, Cellular, and Developmental Biology at the University of Colorado Boulder – knowing that an animal virus can attach to a human cell receptor does not fully clarify its zoonotic potential.

To better understand this, scientists should devise experiments aiming to answer questions such as: If a virus can enter human cells, could it use these cells to make copies of itself and multiply? Can viral particles get past human innate immunity? Have humans ever been exposed to viruses from the same family? 

The answers to such questions would enable scientists to assess which animal viruses may pass beyond their “pre-zoonotic” potential and pose significant threats to human health.

“Where it becomes difficult is that there may be many animal viruses out there with signatures of human compatibility. So which ones do you pick and choose to prioritize for further study? That’s something that needs to be carefully considered,” said Warren.

According to the scientists, a good starting point would be to assume that the viruses posing the most risks to humans come from viral families that have previously infected a variety of mammal and bird species, such as coronaviruses, orthomyxoviruses (which cause influenza), or filoviruses (which cause hemorrhagic diseases like Ebola or Marburg). Other possible candidates may include arteriviruses, which currently cause simian hemorrhagic fever in African monkeys and can easily replicate in human cells too.

Studying animal viruses early to better understand their zoonotic potential could help scientists and medical authorities prepare for their possible spill over to humans and could advance the development of treatments and vaccines. 

“We are continually going to be exposed to the viruses of animals. Things are never going to change if we stay on the same trajectory. And if we stay complacent and only study those animal viruses after they jump into humans, we’re constantly going to be working backwards. We’ll always be behind,” concluded Warren.

By Andrei Ionescu, Staff Writer

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