It’s something you might expect Chicken Little to say: bacteria and viruses are falling from the atmosphere. But five scientists in Spain, the United States, and Canada found viruses are circulating in the atmosphere of our planet – and falling down on Earth. University of British Columbia (UBC) virologist Curtis Suttle said, “Every day, more than 800 million viruses are deposited per square meter above the planetary boundary layer – that’s 25 viruses for each person in Canada.”

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This is the first time researchers have measured how many viruses are carried from the planet’s surface into the free troposphere, where they can be transported for thousands of miles before being deposited down on the surface. The scientists discovered “billions of viruses and tens of millions of bacteria are being deposited per square meter per day” up into the atmosphere, according to UBC’s press release. “The deposition rates for viruses were nine to 461 times greater than the rates for bacteria.”

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Sea spray or dust particles sweep the bacteria and viruses up into the sky – then they tend to be deposited down to Earth with the help of rain or Saharan dust intrusions, according to Universidad de Granada microbial ecologist Isabel Reche.

Suttle said, “Roughly 20 years ago we began finding genetically similar viruses occurring in very different environments around the globe. This preponderance of long-residence viruses travelling the atmosphere likely explains why – it’s quite conceivable to have a virus swept up into the atmosphere on one continent and deposited on another.”

The journal International Society for Microbial Ecology published the research, led by the Universidad de Granada, online late January.

+ University of British Columbia

+ International Society for Microbial Ecology Journal

Images via Nasa and Good Free Photos