New virus catalogue reveals which pathogens pose the greatest threat

Summary

Scientists at the University of Edinburgh have compiled a catalogue of RNA viruses that can infect humans, aiming to identify which pathogens could spark the next major public health emergency. The analysis reaffirms that most viruses found in patients are unlikely to spread between people, as many are zoonotic and require specific conditions to become outbreaks. It also emphasizes that viruses already capable of human transmission pose the bigger pandemic threat, as transmission can intensify if an outbreak reaches dense urban centers. The work connects historical lessons from HIV, SARS-CoV-2, and other pathogens to current surveillance strategies and the rapid identification of potential threats. Original publisher: Nature.

• Two-thirds of viruses on the list are zoonoses with low human-to-human transmission likelihood
• Viruses that already transmit between people dominate pandemic risk
• Historical pandemics inform prediction and preparedness for Disease X
• Faster detection and understanding of new viruses could curb next pandemic toll

Introduction and context

In a typical year scientists discover two to three viruses never seen in people before. While the number fluctuates, the overall pattern has been steady since the 1960s. Most newly identified viruses attract little attention, but some have become infamous through their association with major outbreaks. HIV-1 and SARS-CoV-2 are prime examples that led to decades of global health crises. A team at the University of Edinburgh has been mining the lessons of virus history to help answer a crucial question: how can researchers distinguish a virus that could trigger a pandemic on the scale of AIDS or COVID-19 from one that is unlikely to cause widespread disease?

The researchers recently published a catalogue of human-infective RNA viruses to pinpoint those with the greatest public health risk. This catalogue not only catalogues known threats but also provides a framework for assessing how a virus might behave if it begins to spread efficiently among humans. The authors emphasize that while thousands of RNA virus species have been identified, only a subset has managed to establish disease in people, and even fewer have demonstrated sustained human-to-human transmission across large populations.

What the catalogue shows about pandemic risk

Transmission between people is a key determinant of pandemic potential. Some viruses infect humans but rarely spread person to person, often due to high R values below the threshold needed to sustain transmission. In the article, rabies is cited as an example of a virus that primarily transmits from animals to humans and has not shown sustained human-to-human transmission despite a high clinical burden. In contrast, viruses that already move through human populations, sometimes after crossing from animals, can achieve faster, broader spread, as seen with measles, mumps, and rubella in the past and with different variants of Sars-CoV-2 during the pandemic.

Two major categories of risk

The team divides risk into two broad groups. The first comprises zoonotic viruses that rarely pass from one person to another. While this category includes dangerous pathogens, their ability to generate a global health emergency is unlikely unless the virus undergoes mutations that enable sustained human transmission. The second category consists of viruses with an established ability to spread among people. These can cause sustained chains of transmission, sometimes amplified by factors like population density and mobility, resulting in broad outbreaks and pandemics. The catalogue emphasizes that the latter group represents the more immediate and recognizable threat to global health.

Examples and real-world relevance

Among the viruses that have already crossed into humans and caused major outbreaks are Zaire ebolavirus, Chikungunya, Zika, mpox, and others. Andes hantavirus and Bundibugyo ebolavirus are highlighted as examples of outbreaks that have occurred, including on ships and in central Africa, underscoring that local spread can precede wider transmission. The article also draws on the history of Sars-CoV-2 to illustrate how a virus closely related to one that spreads among humans can emerge from animal hosts with a transmission profile that enables a pandemic scenario. The authors note that neither Andes nor Bundibugyo virus has the profile to trigger a global pandemic under current conditions, but acknowledge that shifts in transmissibility or exposure could change that in the future.

Disease X and the way forward

One of the catalogue’s central concepts is disease X, a placeholder for a future pathogen with the potential to cause a worldwide health emergency. The authors discuss how understanding the relationships among viruses that spread in humans helps identify which ones might look like disease X. They also highlight a counterintuitive finding: viruses that are excellent at crossing species barriers do not automatically become global pandemics. For a future pandemic to unfold, a virus would need a suitable combination of transmissibility, virulence, and opportunities for widespread transmission, such as urban density and international travel.

Lessons for preparedness and speed

A key takeaway is the importance of finding and understanding new viruses faster. The Edinburgh team argues that rapid identification and analysis of emerging viruses could erode the head start enjoyed by pathogens like SARS-CoV-2, potentially reducing the eventual toll on lives and livelihoods. The catalogue thus serves as both a historical lens and a practical tool for guiding surveillance, research priorities, and early interventions in the ongoing effort to prevent the next pandemic from gaining momentum.

Note: The article references prior work and historical pandemics to illustrate how the risk landscape has evolved and how improved surveillance could alter future outcomes.