Classify viruses — the gain is worth the pain

International audience; Earth probably harbours a million times more virus particles than there are stars in the observable Universe. These viruses could hold solutions to many of humanity’s current problems.Phage therapy could someday be used to treat diseases caused by multidrug-resistant bacteria, for instance. Enzymes encoded by new viruses could help researchers to develop pharmaceuticals. Or viruses that kill algal cells could be used to control harmful blooms.Tapping into the benefits — and threats — requires describing and cataloguing viruses and mapping their evolutionary relationships.But, so far, just 4,958 virus species have been formally described.