IMAGINE you are from an alien civilisation, tasked with collecting a sample from Earth to take back to your planet to look for signs of life. You will only be able to return a small representative sample, which means you will be collecting a small amount of seawater from your visit to this "pale blue dot".
In a thimbleful of Earth seawater there will be perhaps 10 million viruses, up to a million microbes and certainly no humans. So it's only a small leap to imagine that, if we ever found life on another planet, viruses would be present too. Why, then, don't space agencies such as NASA and the European Space Agency look for viruses on other planets?
Before we can begin to think about extraterrestrial viruses, however, we need a good understanding of the viruses on our own planet. This is where things get complicated. Although flu and ...
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