"Viruses are critical for species population control. If a certain species becomes overpopulated, “a virus will come through and wipe them out”, Roossinck says. “It’s a very natural part of ecosystems.” This process, called “kill the winner”, is common in many other species as well, including our own – as evidenced by pandemics. “When populations become very abundant, viruses tend to replicate very rapidly and knock that population down, creating space for everything else to live,” Suttle says. If viruses suddenly disappeared, competitive species likely would flourish to the detriment of others."