A study has identified 70 virus lineages – groups of related viruses – that pose the biggest risk. Viruses from other genetic backgrounds are unlikely to cause a high number of infections in humans, the research shows.
The findings will support ongoing efforts to monitor and prepare for future pandemics, including guiding vaccine and diagnostic development, experts say.
Temporal Dynamics, Discovery, and Emergence of Human-Transmissible RNA Viruses; Lu Lu et al
Disease X
Disease X is the generic term used by the World Health Organization to represent a hypothetical, unidentified pathogen that could pose a significant threat to people.
RNA viruses carry their genetic information as RNA, a structure similar to DNA. They cause many diseases, including the common cold, Covid-19 and measles, and have been responsible for most epidemics, or global pandemics, in recent history.
Monitoring RNA viruses in animal populations could help to identify those that are most likely to emerge and spread rapidly in humans. However, the huge number in circulation makes this extremely challenging and expensive.
Tracking viral families
The University of Edinburgh-led research team traced the lineage, or family tree, of 743 distinct RNA virus species to track how they evolved, including all species currently known to infect humans.
Researchers compared the development of strictly zoonotic viruses – those that spread from animals to humans, but not between people – with human-transmissible viruses, which can spread within human populations.
The findings showed that viruses that can spread within human populations typically evolve separately from strictly zoonotic viruses. Human-transmissible viruses often emerge when related viruses from the same lineage can already spread between humans.
Strictly zoonotic viruses have historically not led to epidemics in human populations. Having a close relative that can infect humans, but not spread between them, does not appear to increase the risk of epidemic potential.