New Study Challenges Theories on How Viruses Infect Humans

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A study led by researchers at the University of California, San Diego, has revealed that many pandemic-potential viruses, including SARS-CoV-2, Ebola, and influenza A, can jump directly to humans without first adapting extensively within animal hosts. This challenges the long-held belief that viruses must undergo 'zoonotic preadaptation' before becoming capable of efficient human-to-human transmission.

Why it matters

This discovery has significant implications for pandemic preparedness, as it suggests the key isn't necessarily how adapted a virus is, but how often humans are exposed to a diverse range of animal viruses. As human activities encroach on wildlife habitats, the opportunities for cross-species transmission are growing, raising the risk of new viral outbreaks.

The details

Researchers analyzed the genomes of several viruses and found they already possessed the fundamental ability to infect and spread among humans, even without extensive prior adaptation in animal hosts. This challenges the conventional 'zoonotic preadaptation' theory, which posited that viruses needed to evolve within an animal host before becoming capable of efficient human-to-human transmission.

• The study was led by researchers at the University of California, San Diego.
• The research was published in March 2026.

What’s next

The research emphasizes the need for a proactive, rather than reactive, approach to pandemic prevention, including strengthening regulations on wildlife markets, minimizing habitat destruction, and implementing robust surveillance systems to detect and respond to emerging viral threats.