The Covid-19 pandemic highlighted the importance of pandemic preparation. Now, a new study has identified 70 virus lineages that could provide clues as to which virus might become ‘Disease X’ – an unidentified pathogen that could cause the next global pandemic.
RNA viruses cause diseases such as the common cold, Covid-19 and measles, and have been responsible for a number of global pandemics. These viruses carry their genetic information in RNA – a structure that is similar to DNA.
Understanding the “family history” of these viruses could help scientists to identify which strains may develop into Disease X.
To pinpoint which viruses may go on to cause Disease X, a team of researchers at the University of Edinburgh, Liverpool University and Peking University in China, has traced the lineage of 743 distinct RNA virus species to track how they evolved, including all species currently known to infect humans.
The findings have identified 70 virus lineages that pose the biggest risk.
Professor of infectious disease epidemiology at Edinburgh University, Mark Woolhouse, spoke to Health Tech World to tell us more.
Identifying threats
For the study, published in the journal Molecular Biology and Evolution, the team compared the development of strictly zoonotic viruses – viruses that spread from animals to humans, but not between people – with human-transmissible viruses, which are viruses that can spread within human populations.
The findings showed that viruses that spread within human populations typically evolve separately from strictly zoonotic viruses.
“For the past 25 years we have been trying to better understand which kinds of pathogens are most likely to emerge in human populations,” says Woolhouse.
“One of the very early findings was that 70% of all emerging infectious diseases are caused by viruses. The second thing that emerged quickly from that is that they are likely to emerge from a non-human, animal source.
“Most human viruses have pandemic potential whenever they have emerged from an animal source directly.”
Woolhouse explains that this research narrows the search for the next Disease X enormously.
“One of the concerns about the viruses that we’re interested in, which is mostly RNA viruses, is that these kinds of viruses are known to mutate very quickly,” says Woolhouse.
“The whole nature of influenza is that the virus never stays the same. It keeps changing its antigenicity so that we keep having to use new vaccines protected against it. So, there has always been this concern that the viruses evolve very quickly.
“The 70 lineages that we have identified in the paper, shows that only 70 times have these viruses managed to make the jump into humans, and that gives us a clue. The viruses that are most likely to be able to make the jump are the ones that are closely related to the viruses that have already done it.
“That is where the next pandemic is most likely to come from.”
Preparing for pandemics
The task of surveying all animal viruses for pandemic risk is huge, so focusing on viruses already transmitting between humans could be a more manageable approach to pandemic preparedness.
Utilising sophisticated and well established computer programmes, the team built virus family trees based on the genome sequence data, which tells the team how the viruses are related and about when the ability to spread in humans emerged on a specific family tree.
“We have used machine learning in our work, and the way that machine learning and AI is being used now is to see if you can pick out patterns in the genome sequences that tell you how a virus is going to be.
“We know that what makes a virus able to jump between humans and non-humans is the receptor it uses.”
Identifying the receptors a virus binds to takes years of painstaking molecular biology, explains Woolhouse: “So what do you do? Can you use AI to read the genome so that it tells you which receptor it’s going to and what proteins the virus is going to make?
“You can model the structure of those and see if they fit with any human proteins. If you can do that, from the very first time we find the virus, we can read the genome and tell you an awful lot about the disease and its potential of causing a pandemic.
“You have to get ahead of the curve. You need to find the viruses before they find you. So, how are we going to do it? In our paper we are narrowing down this search.”
The team say the findings will support ongoing efforts to monitor and prepare for future pandemics, including guiding vaccine and diagnostic development.
