What was once seen as a blessing from the heavens became the worst nightmare of the characters in the Scandinavian drama series ‘The Rain’ as a virus carried by rainfall wipes out half of the human population. Viral rain may make a great plot line for any post-apocalyptic TV series, and it’s not all fiction, but there’s no need to panic.

A 2018 study published in Nature revealed that the downward flux of viruses ranged from 0.26x10⁹ to >7 x10⁹ per square metre per day. These rates are 9-461 times greater than that of the downward flux of bacteria. Our planet’s atmosphere is filled with lots of viruses, more than 800 million per square metre to be precise, but how did they get there, and what does it all mean?

Viruses, much like bacteria, are swept up into the atmosphere in small particles from sea spray and soil-dust. The Nature study revealed that the majority of viruses found in the atmosphere showed evidence that they had been swept up from sea spray. This comes as no surprise as it is estimated that there are 10³⁰ virus particles in the oceans alone – that’s one nonillion of viruses in Earth’s five oceans.

The presence of these viruses in the atmosphere may provide insight into why the same virus types are found in different environments across the world. The study showed that once in the sky, viruses can hitchhike thousands of kilometres thanks to wind and fall with the rain in a completely different location to its origin. And, unlike in Netflix’s ‘The Rain’ or even ‘Doctor Who: The Waters of Mars’, these viruses aren’t bad, and some could actually be helping the Earth’s ecosystems stay in check, and allow these ecosystems to adapt to environmental changes.

Almost all of the viruses in the atmosphere infect microbes found in the oceans, so it is highly unlikely that any virus that falls from the sky would infect humans and lead to the post-apocalyptic drama you may see on the big screen or TV. While viral rain may be a real phenomenon, there is no need to panic every time we step outside and find ourselves in the middle of a downpour. This research may not prove the plots of drama series to be true, but it does solve the mystery of why genetically identical viruses are found in different environments and ecosystems across the planet