The aliens among us

Our cover this week focuses on the universe of viruses , a form of life stripped down to the essentials of information and reproduction. Viruses have caused a litany of modern pandemics, from covid-19 and HIV/AIDS to the influenza outbreak of 1918-20. Before that, the colonisation of the Americas by Europeans was abetted by epidemics of smallpox, measles and influenza. Yet the influence of viruses on life on Earth goes far beyond the tragedies of a single species, however pressing SARS-CoV-2 is today. Recent research puts viruses at the heart of the strategies of genes. It is becoming clear how viruses represent the blind, pitiless power of natural selection at its most dramatic. They have shaped the evolution of organisms of all types since the very beginnings of life.  For humanity they present a heady mix of threat and opportunity.