Viruses are constantly falling on our planet. But now, for the first time, a joint study carried out by the Universities of Granada and San Diego has quantified approximately how many of them fall on us. And the figure is about 800 million a day for every square meter.
The authors of the research were aware that genetically identical microorganisms appear in different corners of the planet. That means they've been transported through the air. For this reason, they studied the mechanism and route they follow to travel around the world.
What happens is that viruses and also bacteria, are carried by the wind (through dust particles) to the troposphere, about three thousand meters high. And, at that altitude, microorganisms are susceptible of being transferred at high speed from one continent to another. Something that doesn't happen so easily with particles accumulated in the lower layers of the atmosphere.
Subsequently, it is the rain that causes these viruses and bacteria to fall back onto the earth's surface. The measurements were made in Sierra Nevada, Granada, and also revealed that the amount of viruses transported in this way was about 460 times higher than that of bacteria.