Every year, scientists identify two to three viruses never previously seen in humans. Most disappear into obscurity. But researchers at the University of Edinburgh, led by Mark Woolhouse, decided to stop waiting for the unlucky one and built something closer to a threat map — a systematic catalog of all 239 RNA virus species known to infect humans, ranked by how they spread, what they cause, and whether they could trigger the next pandemic.
Not All Deadly Viruses Are Equal
Lethality grabs headlines, but transmission efficiency determines whether a virus stays local or goes global.
The catalog sorts viruses into three tiers. Roughly two-thirds are zoonotic — you catch them from animals, not other people. Rabies kills tens of thousands annually but has never evolved sustained human-to-human spread. Rabies carries a high body count but lacks the transmission architecture needed to trigger a pandemic. That distinction matters more than any mortality statistic.
The viruses currently on the watchlist:
- Zaire ebolavirus — reached epidemic scale only after hitting West African cities in 2014
- Chikungunya, Zika, and Oropouche — regional outbreaks that expanded when ecological conditions shifted
- Andes hantavirus — a recent cruise-ship outbreak with suspected person-to-person spread prompted WHO to issue high-protection guidance
- Bundibugyo ebolavirus — currently spreading in central Africa
- Mpox — a DNA virus comparator that moved from geographic obscurity to international concern
The top tier is where things get genuinely dangerous: human-adapted viruses with an R-number above one, meaning each infected person spreads it to more than one other. Think measles, SARS-CoV-2, seasonal coronaviruses. Woolhouse’s analysis found that highly transmissible viruses cluster phylogenetically near other human-adapted strains — SARS-CoV-2’s kinship with SARS-CoV-1 confirmed a pattern his team had identified before COVID arrived. According to his work, a novel measles-related virus would carry a far more worrying pandemic profile than Andes or Bundibugyo, which kill efficiently in limited settings but lack the machinery for rapid global spread.
The Algorithm That Hunts Disease X
AI-powered platforms now score over a thousand viruses in near-real time, turning pandemic preparedness into structured data science.
UC Davis published SpillOver in 2020 — an open-source tool ranking wildlife viruses by spillover risk across hundreds of host, viral, and environmental factors. CEPI’s VISTA platform, announced in September 2023, builds on that foundation with AI-assisted scoring of more than 1,000 viruses. It functions like a recommendation algorithm for pathogens, except the stakes are considerably higher than your playlist. The CDC’s Influenza Risk Assessment Tool does something similar for influenza strains specifically, currently rating avian H5N1 clade 2.3.4.4b at “moderate” long-term pandemic risk with low immediate public threat.
Sixty-one percent of emerging infections are zoonotic, and the risk of another pandemic is considered higher now than at any point in recorded history.
Preparedness used to mean stockpiling resources after a crisis arrived. These catalogs and AI tools change that equation. Pre-developing vaccine candidates and broad-spectrum antivirals targeting high-ranked virus families — coronaviruses, influenza, Nipah — means defenses can exist before an outbreak forces the question. For you, that translates to shorter response windows and better-positioned public health systems when the next threat surfaces. The catalog doesn’t predict the next pandemic. It narrows the search, and right now, that may be the most valuable thing science can offer.
