T. bacteriophage viruses and E. coli. (Image: Eye of Science/ Science Source)

Last November, SFI hosted a working group for researchers from a range of disciplines — epidemiology, virology, molecular biology — who came together to compare ideas about viruses.

These pathogenic parasites wreak havoc at small scales by kidnapping cellular machinery to reproduce, at slightly larger scales by infecting tissues within an organism, and at population-level scales by causing widespread disease. Yet the researchers who study these levels lack a united theory of how these scales are all connected.

Last year’s meeting launched an ongoing conversation about such a united theory, but SFI External Professor Santiago Elena, who organized the meeting, says the exchange of ideas also exposed a slew of new challenges.

To address some of those challenges, Elena has convened a follow-up working group, running on November 14-15 at SFI. He has invited a subgroup of participants from the original, including theorists and experimental molecular virologists, to dive deeper into one of the central issues that emerged last year: phase transitions.

In physics, matter undergoes a phase transition when it changes states, as from solid to liquid, or liquid to gas. But Elena, who studies virus evolution at the Institute of Integrative Systems Biology in Valencia, Spain, says emerging evidence suggests biological systems also can undergo phase transitions. Within an infected cell, for example, individual proteins come together to suddenly form the shell, or capsid, of a new virus particle. At the population level, Elena says, the point at which an outbreak becomes an epidemic can also be seen as a phase transition.

This idea emerged at the end of last year’s meeting. “There were people saying yes, saying no, and some people didn’t believe at all in phase transitions,” says Elena. The one thing that was clear was that they needed to keep talking about it. "There just wasn’t enough discussion.”

Elena suspects phase transitions may be a critical step in understanding connections between levels of virus evolution, and he hopes this year’s working group can dive into questions about their role.

“Can we say that phase transitions are universal for viruses at different levels?” he asks. If so, “they might help us see how one level fits on another.”

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