How can researchers tell the difference between naturally occurring and lab-produced pathogens?[

Hundreds of different coronaviruses have been identified, and their genomes have been at least partially sequenced. With coronaviruses, those facts help determine virus evolution.

Mutations occur randomly in any virus, but mutations that give the virus an advantage over other viruses eventually dominate a virus population. When you have hundreds of sequences of viruses from different animal species, you can actually line up the sequences and see how viruses relate to one another.

You can make a “tree” showing those relationships—which viruses evolved from others—and how they have evolved naturally. All that points to a gradual evolution of viruses driven by random mutations and natural selection.

If, however, you uncover a sequence that is only associated with a different virus family—influenza, for example—in a coronavirus, and no other coronaviruses had a similar or related sequence, that would be evidence for some type of engineered virus.

Andrew Pekosz, PhD, is co-director of the Johns Hopkins Center of Excellence for Influenza Research and Surveillance and a professor of Molecular Microbiology and Immunology at the Johns Hopkins Bloomberg School of Public Health.