New RNA virus catalog aims to flag pathogens with pandemic potential

Researchers at the University of Edinburgh have compiled a catalog of human-infecting RNA viruses to help identify which newly detected pathogens deserve urgent attention. Mark Woolhouse, a professor of infectious disease epidemiology at the university, said the tool is meant to distinguish viruses likely to fade from view from those that could spark a wider emergency.

Scientists typically identify two or three viruses each year that have not previously been found in people, Woolhouse wrote in The Conversation. Most generate little public attention, while rare discoveries such as HIV-1 in 1983 and SARS-CoV-2 in 2020 preceded pandemics that killed tens of millions of people, according to figures cited by Woolhouse.

The catalog, published by Woolhouse’s team, focuses on RNA viruses, a group that has driven many major recent infectious disease threats. Researchers have identified thousands of RNA virus species, and Woolhouse said there may be millions more, but the team’s database lists 239 known to infect humans.

Human spread is the key warning sign

Woolhouse said the severity of illness caused by a virus matters, but pandemic risk depends heavily on whether it can pass from one person to another. Transmission can occur through close contact, respiratory particles, blood, feces, or bites from insects and ticks.

About two-thirds of the viruses in the catalog are zoonotic, meaning people usually acquire them from animals and are unlikely to infect other people, according to Woolhouse. Rabies is one example.

Scientists remain concerned that animal-borne viruses could evolve to spread efficiently among humans, a concern that helps explain attention on bird flu, Woolhouse said. But he wrote that there is no documented case of an RNA virus making that shift after being known chiefly as a zoonotic infection, noting that rabies has not done so despite tens of thousands of human cases each year.

The larger danger, according to Woolhouse, comes from viruses that already spread between people. Such viruses may later become more transmissible, as happened with multiple SARS-CoV-2 variants, but they entered human populations with person-to-person spread already possible.

A separate concern involves viruses that can spread among people but have so far produced only limited outbreaks because their average number of secondary infections remains too low. Woolhouse said that can change when a virus reaches new conditions, such as a city after circulating in smaller or more remote communities. He cited the 2014 West Africa outbreak of Zaire ebolavirus as an example.

Outbreak list has flagged later epidemics

Woolhouse said the group of viruses known to have caused limited outbreaks is small but has been useful for anticipating future emergencies. Zaire ebolavirus, Chikungunya, Zika, Oropouche and mpox were previously on such lists and later caused major epidemics, he wrote.

Other listed viruses have recently drawn renewed attention. Woolhouse pointed to Andes hantavirus, linked by the World Health Organization to an outbreak on a cruise ship, and Bundibugyo ebolavirus, which WHO has reported spreading in central Africa.

The catalog may also help researchers think about “disease X,” the term used for a future unknown pandemic threat. Woolhouse said his team reported in 2019 that highly transmissible viruses often resemble viruses already capable of human-to-human spread while emerging separately from animals. He said SARS-CoV-2 fit that pattern because it was related to the original SARS coronavirus and is thought to have come from bats, possibly through an indirect route.

Woolhouse said Andes and Bundibugyo viruses do not have the profile expected of a global pandemic virus. A newly discovered virus related to measles, by contrast, would raise much greater concern because of the traits of that virus family, he wrote.

Recent outbreaks also show the cost of slow detection, according to Woolhouse. He said Andes, Bundibugyo and COVID-19 had all spread for weeks before they were recognized, and argued that faster detection and analysis of new viruses could reduce the human and economic damage from the next pandemic.

This story draws on original reporting from Ars Technica.