Billions of viruses fall from the sky every day, according to new research which could explain why genetically identical viruses are often found in very different environments around the world. In a scientific first, a team of international researchers recorded the number of viruses being swept up daily from the Earth's surface into the free troposphere - the lowest layer of the atmosphere, in which nearly all weather occurs. The study, published in the International Society for Microbial Ecology Journal, describes the detection of hundreds of millions of viruses and bacteria raining down from the sky on a daily basis. "Every day, more than 800 million viruses are deposited per square metre above the planetary boundary layer - that's 25 viruses for each person in Canada," study co-author and University of British Columbia virologist Curtis Suttle said in a statement. Bacteria and viruses are swept up into the atmosphere in small particles from soil-dust and sea spray. The pathogens can