Bacteria and Viruses Are Raining Down on Us All the Time

Thanks to Brilliant for supporting this episode
of SciShow. Go to to learn more. [♩INTRO] Growing up, you may have heard that you can
catch a cold in the rain. And it turns out there’s some truth to that
idea. See, pathogenic organisms stuff like viruses and bacteria that can give
plants and animals diseases do rain down on us all the time, with or without
the help of water. But the situation isn’t so dire that you’re
likely to get sick from going outside… yet? According to a 2015 study published in the Proceedings of the National Academy of
Sciences, we may inhale thousands of microbes per hour
when we’re breathing in “fresh air”. These organisms come from almost anything
you can think of: the soil, bodies of water, even the surfaces
of plants and buildings. And they’re not necessarily from the immediate
vicinity. Winds, splashing water, rising smoke, and
many human activities can dislodge microorganisms from their dwelling places
and launch them into the air. Once afloat, they can snag onto small particles
like dust and travel way up into the atmosphere, into a region known as the planetary boundary
layer. And there, they can move thousands of kilometers with the air masses they’re suspended in,
across whole continents and oceans. Eventually, though, they fall back down, either in rain or when the particles they’re
associated with finally settle. And scientists estimate that hundreds of millions
of viruses and tens of millions of bacteria rain down
in this manner on every square meter of this planet every
day. That’s… not the worst part. You see, scientists say these globe-trotting
microbes can spread diseases around the globe. For example, in 2004, a pathogen that infects
plants traveled from Asia to the United States thanks
to a hurricane. And a 2003 paper published in BioScience suggested
that the global transport of dust could be sprinkling
pathogens onto coral reefs. Poor coral reefs just can’t catch a break,
can they? Luckily, if you’re a human, you probably
don’t have too much to worry about. Most of the microorganisms moving around this
way are considered harmless. …Though, not all of them. Scientists have found potential pathogens
like Staph in the dust that settles after storms and
during dust events. And in some cases, they think wind patterns
can explain disease outbreaks. For example, in 2011, researchers found that
epidemics of Kawasaki disease correlated with wind currents that swept from
Asia to the north Pacific. Kawasaki disease is an illness that causes
inflammation in blood vessels, particularly in kids. And the weird thing is, we don’t actually
know which pathogen is responsible. So the wind pattern connection, while not
definitive, could be an important clue for medical researchers trying to better understand
the disease. Also… even if there’s no immediate link
between human disease-causing pathogens and the billions
upon billions of microbes falling from the sky every day, there could
be soon. See, this whole situation is probably getting
worse with climate change. Scientists think it’s likely that even more
dust and microbes will float into our atmosphere in the coming decades thanks to things like increased desertification
and more intense weather events. So, while you might not catch a cold or any
other disease from the rain in the near future, the possibility is only
increasing. Researchers have to use a lot of really complex
math to figure out how pathogens move around in the clouds and how
that might change in the future. And that math is something everyone can learn
with You see, Brilliant offers dozens of courses
that cover topics in science, engineering, computer science, and math. And their Differential Equations 2 course
dives into the hardcore math needed to predict weather patterns, as well
as other kinds of scientific modeling. With a premium subscription, you’ll get
access to it and all their other courses, as well as engaging Daily Challenges which help you practice the skills you’re
learning. And right now, the first two hundred people
to sign up at will get 20% off an annual premium subscription. So check it out! And let us know if you learn anything really
cool in the comments. [♩OUTRO]

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