According to a new study recently published in Nature and carried out by scientists from Canada, Spain and the USA, a gigantic number of viruses are circulating around the Earth through the troposphere (the first layer of the atmosphere above the Earth’s surface), something so far greatly underestimated.
The study is the first to quantify the number of viruses being swept off the planet’s surface, via dust particles and aerosols formed in the oceans (as well as bacteria), and ending up in the troposphere, where they can cover thousands of kilometers before returning to the surface, free of or associated with organic particles in the lower atmosphere (although these associations are much less intense than those observed in bacteria).
According to the results of this quantitative analysis, between 260 and more than 7 billion viruses are deposited per square meter from the troposphere to the Earth’s surface daily, depending on the region.
This deposit is between 9 and 461 times higher than the rates observed for bacteria, which range from 3 million to more than 8 million bacteria per square meter daily.
Considering that viruses and bacteria seem to form aerosols with the same ease on the surface of the seas, glaring differences in deposition between both organisms is explained by the greater resistance of viruses to be swept out of the atmosphere by rains and dust particles, unlike bacteria, drastically increasing their concentrations in the troposphere.
In addition, virus deposition rates were positively correlated with organic aerosols smaller than 0.7 micrometers, while bacteria were primarily associated with organic aerosols larger than 0.7 micrometers, implying that viruses may have a longer residence time in the atmosphere and, consequently, be dispersed farther, fueling local deposition rates at different points in the world.
This huge amount of viruses persistently sailing through the skies more than explains the scientific observation more than 20 years ago that genetically similar viruses could be found in different parts of the globe.
Viruses are by far the most abundant microbes on the planet, with an estimated 10^30 (number 10 followed by 30 zeros) viral particles in the oceans alone.
Making up much of the planet’s biological diversity and negatively or positively affecting populations in all kingdoms, it becomes more than important to understand their distribution patterns in the environment.
