Scientists discover two or three new human viruses every year. Most fade into obscurity. A few — HIV, SARS-CoV-2 — kill tens of millions. The question is: how do you tell the difference before it’s too late?
A team at the University of Edinburgh built a catalog to answer that. They published it in Nature Scientific Data. Of thousands of known RNA virus species — maybe millions — only 239 infect humans. The catalog helps pinpoint which ones are dangerous.
Key insight: two-thirds of human-infecting viruses can’t spread between people. Zoonotic viruses like rabies come from animals and stop there. That sounds reassuring, but viruses evolve. Bird flu is the big worry right now — though there’s no documented case of an RNA virus gaining human-to-human transmission after being purely zoonotic.
The real threat is different. It’s viruses that already spread between people but have low R numbers. Limited outbreaks that fizzle out — until they don’t. Zaire ebolavirus in West Africa 2014 is the textbook example. Confined to remote villages, then it hit a city.
The team’s “outbreak list” is small — a few dozen names — but predictive. Every virus on it has caused major epidemics: Zaire ebolavirus, Chikungunya, Zika, Oropouche, mpox. Newer entrants like Andes hantavirus (recent cruise ship outbreak) and Bundibugyo ebolavirus (currently spreading in central Africa) validate the model.
The scariest scenario? A novel measles-related virus. That would be worse than COVID. Measles is one of the most transmissible viruses known. A relative with the same spread characteristics would be catastrophic.
The lesson from both Andes and Bundibugyo: they spread for weeks before detection. So did COVID. Faster virus discovery and better surveillance could deny the next pandemic the head start it needs.
