Viruses fall back to Earth via dust storms and precipitation, according to new research published in the International Society for Microbial Ecology Journal.
Viruses are circulating in the atmosphere of our planet. Image credit: Arek Socha.
“Every day, more than 800 million viruses are deposited per m2 above the planetary boundary layer,” said Dr. Curtis Suttle, a virologist at the University of British Columbia.
“Roughly 20 years ago we began finding genetically similar viruses occurring in very different environments around the globe.”
“This preponderance of long-residence viruses traveling 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.”
Bacteria and viruses are swept up in the atmosphere in small particles from soil-dust and sea spray.
Dr. Suttle and co-authors wanted to know how much of that material is carried up above the atmospheric boundary layer above 2.5-3 km. At that altitude, particles are subject to long-range transport unlike particles lower in the atmosphere.
Using platform sites high in Spain’s Sierra Nevada Mountains, the team found billions of viruses and tens of millions of bacteria are being deposited per m2 per day.
The deposition rates for viruses were nine to 461 times greater than the rates for bacteria.
“Bacteria and viruses are typically deposited back to Earth via rain events and Saharan dust intrusions,” said co-author Dr. Isabel Reche, a microbial ecologist at the University of Granada.
“However, the rain was less efficient removing viruses from the atmosphere.”
The researchers also found the majority of the viruses carried signatures indicating they had been swept up into the air from sea spray.
The viruses tend to hitch rides on smaller, lighter, organic particles suspended in air and gas, meaning they can stay aloft in the atmosphere longer.
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Isabel Reche et al. Deposition rates of viruses and bacteria above the atmospheric boundary layer. The ISME Journal, published online January 29, 2018; doi: 10.1038/s41396-017-0042-4
