Scientists already have a list of contenders ready.

SARS-CoV-2 surprised us. We did not see the virus coming and could only watch it passively conquer the world. Researchers believe that this should change in the future. And so they have come up with a way to quickly identify which (newly discovered) animal viruses have the best chance of jumping to humans and causing a pandemic.

Risk factors
Whether an animal virus succeeds in spreading to people and subsequently infecting many other people depends on various (risk) factors. In the magazine Proceedings of the National Academy of Sciences researchers identify dozens of these risk factors. Some are inherent in the viruses themselves. Others depended more on the environment. For example, frequent contact between people and animals that (can) carry these viruses is also a risk factor.

Next, researchers used these risk factors for 887 animal viruses to determine how likely they are to pass to humans. This results in a ‘watch list’ of viruses that could pose a threat to global public health. At the top we find 12 viruses that are known to have already passed from animals to humans – including SARS-CoV-2. According to the researchers, it confirms that their risk assessment is on the right track.

Surprises
If we take a look at the watch list, there are a number of surprises. For example, the virus that is currently causing a lot of misery worldwide is not at the top. In the list of zoonoses that have the potential to cause a pandemic, SARS-CoV-2 is in second place; the ranking is led by the lassa virus. That may seem strange, but according to the researchers it is not. For example, they point out that we still do not know everything about SARS-CoV-2. For example, it is unknown in which animals it can live and the size of the area in which these animals occur. If we had all the information, maybe the virus would top the rankings.

New viruses
What is also surprising is that, according to the researchers’ risk assessment, several coronaviruses recently discovered in animals are more likely to pass to humans than some viruses that have already been shown to pass to humans. An example of this is PREDICT_CoV-35. This corona virus has recently been discovered and is one of the twenty viruses that make up the watch list.

Expansion
If it were up to the researchers, the watch list will be expanded considerably in the coming years. On the basis of their research, they have developed a web application with which discoverers of new viruses can immediately determine the chance that ‘their’ virus will pass from animals to humans. Researchers can also use site add new information on known viruses, which can improve the risk assessment. The researchers hope the application – called SpillOver – will enable researchers to identify new threats in a timely manner. After which, timely measures can also be taken to reduce the chance of the virus spreading from animals to humans. “SARS-CoV-2 is just one example of the many thousands of viruses that have the potential to transfer from animals to humans,” said researcher Zoë Grange. “We must not only identify the viruses that are most likely to pass from animals to humans, but also prioritize them before another devastating pandemic occurs.”

We have seen in the past year that zoonoses are a real threat. In addition to SARS-CoV-2, researchers are also known about 250 viruses that have already passed from animals to humans and have made humans sick. However, it is not the already known zoonoses that researchers are particularly concerned about. The main concerns concern the zoonoses that have not yet been discovered; Scientists estimate that mammals and birds still have about 1.67 million undiscovered viruses, of which up to 50 percent have the potential to transfer to humans. The challenge now is to identify those viruses and make an immediate assessment of the risk they pose. And so this new research can help with that. “SpillOver can increase our understanding of virus threats and enable us to take measures to reduce the likelihood of viruses spreading from animals to humans,” said researcher Jonna Mazet.