India, March 11 -- Viral adaptation is not a necessary precursor to outbreaks of novel zoonotic viruses, says a new study published in Cell on March 6, 2026.

Using a phylogenetic framework to characterise natural selection, researchers led by Jennifer L Havens of the University of California investigated the hypothesis that zoonotic viruses require adaptation before zoonosis to sustain human-to-human transmission.

The researchers analyzed the evolutionary histories of several major viral outbreaks, including COVID-19, the 2009 H1N1 influenza pandemic, the 2013-2016 West African Ebola virus disease (Ebola) epidemic, the 2004-2005 Angolan Marburg epidemic, and the 2022-2023 mpox epidemic.

No evidence was found of a change in selection in...