All over the world it is raining viruses – but the outlook is not too bleak.
For the first time scientists have measured the extent to which viruses are being carried into the atmosphere before falling back to Earth.
The findings suggest a deluge of biblical proportions, with countless billions of the particles raining down constantly on every part of the planet.
Virus rain may explain why genetically similar viruses are found in different parts of the world (Curtis Suttle, University of British Columbia/PA)
Each day more than 800 million viruses are swept up in sea spray and dust and deposited in each square metre of the atmospheric layer above the Earth’s weather boundary, the study found.
There they collect and travel around the world before being being transported back down by rain or falling dust.
The discovery helps explain the puzzle of identical viruses turning up in distantly separated parts of the world.
Lead scientist Dr Curtis Suttle, from the University of British Columbia in Canada, 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 researchers investigated how many viruses made it to the free troposphere, the atmospheric layer above 2,500m (8,202ft) and 3,000m (9,842ft) beyond the reach of ground-influenced weather.
At that altitude particles can easily be transported long distances.
Viruses were sampled using platforms high in Spain’s Sierra Nevada mountains, within the free troposphere.
The scientists found billions of viruses, as well as tens of millions of bacteria, being deposited on their collection sites.
The deposition rates for bacteria were up to 461 times greater than for bacteria.
Most of the viruses carried hallmarks indicating they had been swept up into the air by sea spray.
While people may baulk at the idea of being showered by viruses, most of the particles cause no harm and some are beneficial.
Viruses help maintain balanced ecosystems and certain types called bacteriophages may protect human health by killing bacteria.
The research is published in the International Society for Microbial Biology Journal.