The majority of what scientists know about viruses in animals comes from the list of nucleotides that constitute their genomic sequence, which, although useful, provides relatively few signals about a virus’ propensity to infect people.
Two virologists contend in a Science Perspective article that was published on March 10th, 2023, that the scientific community should invest in a four-part research strategy to proactively detect animal viruses that could infect people rather than letting the next pandemic catch everyone off guard.
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 is just a fallacy.”
Cody Warren, Study Co-Lead Author and Assistant Professor, Veterinary Biosciences, The Ohio State University
He added, “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 is a realistic way of looking at things that should also be considered.”
Sara Sawyer, a professor of molecular, cellular, and developmental biology at the University of Colorado Boulder, and Warren collaborated on the opinion article.
Warren and Sawyer wanted the public to comprehend that just because an animal virus can bind to a human cell receptor, it does not mean it has zoonotic potential.
They suggest a set of trials to determine an animal virus’ ability to infect humans: If it is discovered to infiltrate human cells, can it exploit those host cells to replicate and multiply? Do viral particles survive human innate immunity once they are produced? Has the human immune system ever been exposed to another virus from the same family?
Addressing these questions might allow scientists to put a pre-zoonotic candidate virus “on the shelf” for future studies, such as establishing a simple technique to detect the virus in humans if an unattributable disease appears and evaluating current antivirals as potential therapies, according to Warren.
“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 is something that needs to be carefully considered,” Warren added.
Warren and Sawyer believed that assuming that the viral families that are currently infecting mammals and birds as “repeat offenders” would be a good place to start when determining which viruses pose the greatest threat to humans.
Coronaviruses, orthomyxoviruses (influenza), and filoviruses (causing hemorrhagic diseases like Ebola and Marburg) are some of them. A new ebolavirus named Bombali was discovered in bats in Sierra Leone in 2018, however, it is yet uncertain if it can infect people.
Then there are arteriviruses, like the simian hemorrhagic fever virus found in wild African monkeys, which Sawyer and Warren recently found has a fair chance of spreading to people since it can reproduce in human cells and undermine the ability of immune cells to defend themselves.
Warren pointed out that the disastrous consequences of the advent of SARS-CoV-2 could have been far worse. The 2020 global lockdown to prevent the spread of COVID-19 is still a recent and bitter memory.
Vaccines were available within a year of the shutdown only because scientists had spent decades studying coronaviruses and understood how to tackle them.
Warren further stated, “So if we invest in studying animal viruses early and understand their biology in more detail, then in the case that they were to emerge in humans later, we would be better poised to combat them.”
He concluded, “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 are constantly going to be working backwards. We will always be behind.”
Warren, C. J., et al. (2023). Identifying animal viruses in humans. Science. doi.org/10.1126/science.ade6985