Articles, Blog

The Baffling Viruses That Infect… Other Viruses

January 5, 2020

This episode is supported by NordVPN. Right now, NordVPN is offering SciShow viewers
a chance to set up your own Virtual Private Network and start protecting your internet
experience today with 77% off a 3-year plan. Use the code “SCISHOW” at [♪INTRO] Viruses make so many people sick and miserable
that it seems like turnabout—it’s only fair play! Make the viruses get sick for once! But that’s ridiculous… right? Well, maybe not. Virus-infecting viruses, or virophages, are
totally real, because evolution just doesn’t know when to quit. The first virophage, named Sputnik, was discovered
in 2008 by a team of French researchers in a Parisian water tower. But they didn’t discover it alone. Pretty much everything we learn about these
extremely small viruses is linked to the extremely big viruses they infect, called giant viruses. And since giant viruses, like mimiviruses
and pandoraviruses, were only discovered in 2003, this whole field is brand new territory. Giant viruses were discovered infecting amoebas,
and have been found all over the world. It’s not entirely clear whether they can
make humans sick or not. They’ve been isolated within humans a few
times, including people sick with pneumonia, but it’s not 100% clear if they were causing
the illness or just hanging out. And they’re huge… relatively speaking. In terms of their size and genetic complexity,
giant viruses are more like bacteria than most other viruses. Like, mimiviruses are about 500 to 800 nanometers
across and have genomes of around 12 million base pairs. And pandoraviruses are even bigger. Now, mimiviruses are preyed upon by the Sputnik
virophage, which is only 50 nanometers across and has a genome of about 18,000 base pairs. That’s actually not super small for a virus. The bacteria-infecting virus lambda forms
particles of a similar size, and the flu virus actually has a smaller genome. But what’s weird is that even though giant
viruses are big, it doesn’t seem like they should be able to support invaders. Especially since virophages are still…viruses. They’re made of DNA and protein, but they
lack all the cellular replication tools needed to copy DNA, and the translation tools needed
to make proteins. That’s why viruses need hosts. They enter host cells and take over cellular
equipment to make little virus factories. Without a host cell, viruses would never reproduce. And, in this case, the hosts are…also viruses. Mimiviruses can’t copy DNA and protein on
their own either, and have to infect an amoeba to reproduce. That’s where the virophage sneaks in. It infects the mimivirus while it’s infecting
the amoeba and borrows the giant virus factory. So instead of making more giant viruses, the
amoeba churns out the virophage copies instead. This directly harms the giant virus and its
efforts to reproduce, which is what leads researchers to say that virophages are parasites
of giant viruses, not of amoebas. Now, giant viruses are kind of special because
they seem to have some of that cellular equipment, like a few genes involved in protein translation. But they don’t have ribosomes, the big factories
that actually string proteins together. So they can’t get the job done all by themselves. That’s why many biologists exclude viruses
from the tree of life that includes bacteria, archaea, and eukaryotes. If viruses can’t replicate on their own,
they’re not really alive. Scientists can compare various genes to determine
evolutionary relationships, but if you want to go back to the very beginning, you have
to compare something that all cellular life has. That’s ribosomes. Scientists line up the gene sequences of ribosomes
to determine who’s most closely related to whom. Since viruses don’t have ribosomes, that
means there’s no way to fit them into that paradigm. Viruses have historically just not been considered
enough to count as life. Not enough complexity, not a big enough genome
to fit in the same camp as life as we know it. But there’s still a debate going on. Like, maybe we’re being cell chauvinists. After all, viruses don’t have ribosomes,
but we cellular organisms don’t have capsid proteins, which form the coats of many viruses. And giant viruses are supercharging that debate
because they are more complex and they do have big genomes. Not to mention, they have some of that protein-making
machinery that was thought to be unique to us proper protein-making cellular creatures. And the discovery of virophages has fired
things up, too. Virophage DNA can become integrated into the
DNA of its host virus, just like other viral genomes can integrate into cellular hosts. So if giant viruses can be preyed on like
cells… maybe that’s an argument that we should think of them as being more alive. At least, according to some scientists. We’ve only discovered 18 types of virophages
so far, in places as diverse as lakes in Antarctica to contact lens fluid in France. Many of those are just hits in genome searches,
meaning sequences similar to known virophages have turned up in genomic studies. Nothing about them has actually been studied
in detail yet, so we don’t know what they look like or what they infect. Which only sort of counts as discovering them. But it seems like there could be plenty more
of them out there, and virophages and giant viruses might be more common than we expect. The question of whether viruses are alive
isn’t something we’re going to answer in a 4 minute video… because it’s not
something that biologists are going to settle any time soon. The more we try to categorize evolution in
neat boxes, the more curveballs it throws us. It’s a virus-eat-virus world out there. Thanks to NordVPN for sponsoring this episode. I love the internet and I spend a lot of time
on it. But, as much as I love it, the internet is
not always as secure as I would like it to be. With NordVPN, you can make your connection
to the internet safer. Everything you send over a private, password-protected
internet connection is encrypted, which keeps it safe from snoopers. But say you’re watching a SciShow video
in a coffee shop—so, on a public unsecured network—that’s great! May I recommend this episode on caffeine? The thing is, anyone can see what you’re
doing on a public network. This is why websites that involve sensitive
information, like your bank, have H-T-T-P-S in the URL which means everything you do on
that site is encrypted. But even sites that use https can be vulnerable
to more sophisticated attacks. With a VPN (or Virtual Private Network) all
of your data gets encrypted before it ever leaves your computer, then re-routed through
a trusted server before it’s sent onto the site. In the other direction, data sent to you by
the other side is encrypted by the server before it gets to you. So your personal information is totally safe
sounds complicated, but NordVPN does it all for you with over 4400 super fast servers
in 62 countries, and they’re adding new secure servers all the time. And whether you check your private information
on your Android phone, or iPad, or your ChromeBook, NordVPN will work across different operating
systems and one plan can be used on up to 6 devices. Use the code “SCISHOW” and sign up at to get 77% off a 3-year VPN plan. [♪OUTRO]


  • Reply roddy axolotl September 1, 2019 at 10:35 pm

    Look i dont mean for a huge battle royale argument but i think viruses are alive, i mean hear me out,
    i dont want a damn argument in the replies you got that

  • Reply Bass Dat September 5, 2019 at 6:17 am


  • Reply Uri Neri September 6, 2019 at 9:12 am

    @SciShow Which mimivirus has a 12 Million base pair genome?? isn't it more like around 1Mbp?
    And Pandoraviruses have around 2 million bases.
    These are HUGE genome sizes for viruses, more than some microbes…

  • Reply Parker Phillips September 7, 2019 at 2:28 pm

    Me me big virus

  • Reply ihatecrackhead September 9, 2019 at 12:40 am

    viruses are alive if you consider cells of other living things a natural resource

  • Reply Vanalovan September 9, 2019 at 6:28 am

    So is there a virus McAfee?

  • Reply NeonBee September 10, 2019 at 6:29 pm

    I believe viruses to be alive in a certain sense because they carry a purpose, though they need something living with which to carry out the purpose. If viruses didn’t have a specific purpose, if they didn’t reliably ‘carry out the same plan’ in order to ‘live’, I would agree they fit very little of the criteria we usually use to consider things alive, and don’t even have a ‘goal’. Setting aside how they reproduce, how they don’t need energy, and their lack of temperature control, like all life, they have a certain purpose they ‘want’ to carry out, it seems. Life is more fluid than I think we humans like to think, for instance, with the weak force being an exception in many ways, viruses are the weak force of the micro world in my eyes. They are not technically living under the controls we have seen in a vast majority of living beings, but because they live differently, entirely, doesn’t mean they don’t live in my mind. I don’t think they necessarily start living until they come in contact with their host though, but I would compare it to something that has the potential to be a life. A bunch of cells growing in a woman’s womb is not a baby, yet. Talking about the egg, it has the plan, it does not have the means, but when it gets the other parts in needs (sperm), life is created.

  • Reply Lee Matthew September 12, 2019 at 12:51 pm

    You blokes are way behind the times. Phage therapy has been done for decades in Georgia.

  • Reply Matthew Schultz September 12, 2019 at 10:05 pm


  • Reply Lalu September 13, 2019 at 12:22 am


  • Reply Blue Roots Denver TV September 13, 2019 at 1:21 pm

    Good video thank you.

  • Reply Chet Jonstun September 13, 2019 at 7:34 pm

    Hang on. I can't reproduce on my own.
    Does that mean that I am not alive either?

  • Reply Tengku Aliff September 14, 2019 at 5:12 am

    Like humans are to other humans lool

  • Reply Joseph September 14, 2019 at 7:24 am

    "Ohh, yout genom is soo big!"

  • Reply Hi September 14, 2019 at 9:31 pm

    Team-kill: On

  • Reply Rajat Prakash September 14, 2019 at 10:49 pm

    its virusception

  • Reply Russel Edward Teves September 15, 2019 at 7:14 am

    Could it be done on HIV?

  • Reply Raezores September 15, 2019 at 8:58 pm

    Is the last member of a species not alive?

  • Reply Bitelaserkhalif 555 • September 15, 2019 at 10:40 pm

    HIV potential cure?

  • Reply Random Me September 16, 2019 at 12:21 am

    Now viruses can get the taste of their own medicine!

  • Reply Evilpimp September 16, 2019 at 5:16 am

    Enemy of my enemy is my good buddy old pal

  • Reply Oc Boi September 16, 2019 at 10:25 am

    I use virus, to destroy virus

  • Reply Alexis September 16, 2019 at 11:09 am


  • Reply Andrew Miller September 16, 2019 at 5:59 pm

    Idk about the argument that viruses arent life because they cant produce on their own. What about all of the complex parasites that need hosts to reproduce??

  • Reply Dorothea Chia September 19, 2019 at 2:11 am

    cell-chauvinist… what an awesome term. Thanks!

  • Reply naxel37 September 19, 2019 at 8:38 pm

    Sputnik, like the satellite.

  • Reply Donny Fraley September 19, 2019 at 9:36 pm

    I have absolutely no idea what you just said. Really, nothing.

  • Reply David September 23, 2019 at 11:07 am

    “The enemy of my enemy is my friend”

  • Reply Michael Elbert September 23, 2019 at 4:30 pm

    Do they replicate their own …DNA?

  • Reply Jim Mauch September 25, 2019 at 8:21 pm

    Are we talking about turtles all the way down?

  • Reply make women property again September 27, 2019 at 7:17 am

    Retarted witty cooments nothing related to the content

  • Reply Dale Hartley September 28, 2019 at 7:44 am

    Life. But not as we know it…

  • Reply Ade Alpha TV September 28, 2019 at 5:53 pm

    hey buddy👋iII Be streamlng the KslvsLogan fight🥊Turn on my notifsscations

  • Reply JP September 30, 2019 at 4:06 am

    Mimiviruses are named after Mimi from the Drew Carey show

  • Reply Shamsheer siddiqui October 1, 2019 at 12:52 pm

    Looks like Parasitic virus

  • Reply Wick Bobby October 1, 2019 at 3:41 pm

    can this be a cure

  • Reply Raul Lopez October 3, 2019 at 5:19 am

    What if you genetically modified a virophage to infect the herpes simplex virus, causing it to no longer create more of its virus, but instead produce a harmless virophage?

  • Reply motor head1 October 4, 2019 at 2:04 pm

    How does something without a "brain" figure out how to change itself and evade immune system or attack anything????
    Prion and ribosome also no neurons no brain yet "intelligent"??

  • Reply Conteúdo Original October 4, 2019 at 6:51 pm

    "you became the one that you swear to destroy"

  • Reply Cats game lover vibes October 4, 2019 at 7:06 pm

    Viruses: the body cells going to be out in lunch

    Bacteriophages: I don't think so

  • Reply Commander Sus Gunner October 6, 2019 at 11:34 pm

    No u

  • Reply White Blogger Black Specs October 10, 2019 at 10:08 am

    Can we give Ebola the flu and vice versa? >:3

  • Reply estro ssa October 10, 2019 at 9:07 pm

    Viruses r artificial……

  • Reply orangequant October 11, 2019 at 9:21 pm

    Very annoying debate. Back to basics. There's Mineral, Animal, and Vegetable kingdoms (Human, imo, being wrongly considered as Animal). Anyway, viruses are neither Mineral nor Vegetable. Ergo, they are Animal, meaning "alive".

  • Reply JASSON REYES October 12, 2019 at 5:25 pm

    Using virus to combat virus?
    Using water to combat fire.

  • Reply Bachelor Boy October 13, 2019 at 6:45 am

    Karma hits everyone!

  • Reply Carlos Acevedo October 13, 2019 at 10:50 am

    Hank recommends this episode on caffeine. I recommended to watch it on tethrahydrocannabinol

  • Reply vrg kard October 16, 2019 at 2:36 pm

    Nice haircut I envy you

  • Reply nazgulius October 16, 2019 at 5:57 pm

    Dam commercials thumbs down. And nord streams all data so u not realy protected.

  • Reply Naim Noor October 17, 2019 at 9:28 am

    Mimivirus? Mimi? Mariah Carey?

  • Reply electr0 October 18, 2019 at 4:49 am


  • Reply Vulpovile October 18, 2019 at 6:41 am

    I wonder if virophages would one day be used to treat viral infections

  • Reply Calder Johnson October 19, 2019 at 4:19 am

    Even before I entered this comment section I heard the puns echoing in my head.

  • Reply Eric Scott October 19, 2019 at 7:13 am

    Yes 👍 Even fleas have fleas.

  • Reply Cool Sh!t October 19, 2019 at 7:58 pm

    Does this mean they are living if they infect themselves?

  • Reply Raphael Mejia October 20, 2019 at 11:46 pm

    Virus: im invincible, no one can infect me

    Virophage: hippity hoppity, your genetic replication machine is now my property

  • Reply Hashtag No name October 23, 2019 at 4:16 pm

    Next Discovery: Found a Virus infecting a Virus infecting a Virus infecting an amoeba infecting a person.

  • Reply Troy Baker October 25, 2019 at 12:33 am

    Welcome to scischow where the science isn’t science but you should accept it as fact as if it was.

  • Reply Billy Eyelash October 25, 2019 at 7:42 am

    oof too bad nordvpn got hacked

  • Reply Kim son Luu October 25, 2019 at 3:28 pm

    there's also bacteriophage

  • Reply Jam Bos October 27, 2019 at 12:30 am

    NordVPN ain't keeping you safe from the NSA, so…

  • Reply yesn't October 27, 2019 at 9:58 pm

    well this sponsor aged well

  • Reply Discovaria October 28, 2019 at 2:49 am

    But mimivirus only kills amorba

  • Reply Jackson Stein October 29, 2019 at 10:21 pm


  • Reply SRC November 3, 2019 at 9:58 pm

    Don’t ever for get who is the powerhouse of cells…

  • Reply Seth Malovany November 5, 2019 at 1:14 pm

    Why don't you mention Viroids and Virusoids ie, Potato Spindle Viroid?

  • Reply Paul Rondezca November 5, 2019 at 4:10 pm

    Wait, is there a way to make a computer virus that infects other computer viruses?

  • Reply mikearmani2 November 6, 2019 at 2:21 pm

    You need a giant host to survive too… The Earth. Viruses are so alive

  • Reply WAQUAR AHSAB November 6, 2019 at 2:32 pm

    Can giant viruses infect humans?

  • Reply harshbarj November 6, 2019 at 4:16 pm

    Well, that sponsor did not age well.

  • Reply Tony Mathis November 8, 2019 at 6:23 am

    So Giant Viruses are Democrats and Virophages are Progressives.

  • Reply Ian Moone November 10, 2019 at 3:39 am

    an antivirus virus

  • Reply Jimmy R. November 10, 2019 at 5:18 pm

    I used the virus to destroy the virus.

  • Reply Ghiman the guy November 11, 2019 at 6:42 am

    I disagree that viruses arent alive. I believe that anything that has a will, drive, and ability to survive for several generations, is alive. Idk how this wouldnt be the base for life. That's what all living things do, strive to extend their lineage, and extend their own life as well.

  • Reply Thiantrus November 11, 2019 at 4:45 pm

    If there is viruses that infect viruses for example virus a infect virus b now virus b infects a human. Now instead human body reproduce b it reproduce a. If i understand the video correct why don't they infect HIV/Aids with a virus totally engineered for it that's harmless to humans or am i grabbing at straws.

  • Reply Picani Georgello November 12, 2019 at 4:43 pm

    Ad reads that dont age well LMAO

  • Reply rockets4kids November 14, 2019 at 1:02 am

    Yo dawg…

  • Reply Tony Clynch November 14, 2019 at 10:49 am

    If you want to find out more about viralphage ask the Russians they have been working with them since the 70s

  • Reply Daniel Bojidarov November 15, 2019 at 9:12 pm

    i'd like to give you a tip , take ingredients like chop meat , cotton , maybe just a bit soil , proteins and some human leftovers like skin hair , anything and seal it inside a container for 2 to 5 weeks , the idea is to get smooth rotten pasta by itself without doing anything , than use equipment gloves mask and glasses and a lot of Spirt(100%alkohol) afther you transport it into spraying bottle with fairly warm water , seal the bottle verry well so nothing will get on your hands and spray at Car holds , on your enemy-s whatever ATM-s , and anywhere it should get them killed or seriously injured that's all i have to say
    Vinegar and Lemon juice should be good antidote if you accidently get some of it in your organism, trust me you would understand it .. The antidote should be around 90 Lemon ml and 130 Vinegar + bit salt or suger and a Long Hot shower and all should get out ! 🙂

  • Reply zaini adnan November 16, 2019 at 11:55 am

    Somewhere up there God created this and think this is funny

  • Reply thecolorthursday November 17, 2019 at 12:11 pm

    Even if viruses aren't alive, they still evolved. If you had a tree of life that went all the way to the first organisms, viruses would've been somewhere on there.

  • Reply Jaydeep Vipradas November 24, 2019 at 11:46 am

    Can't wait for viruses to evolve such that they produce nanobots 😈 , replication looks like main business rather than evolution and gaining capabilities! 🤔
    Purpose of genes should be tapping into universe's infinite energies, along with replication and gaining capabilities. Which looks hard as universe is complex at quantum level and could be multi-dimensional. But universe's basic thing is that anything can not be exactly replicated at physics level and hence genes are used to compensate differences to some extent.
    Machine makes machines but not of same type. For better understanding of things, Fractal type design can be studied, where by design, fractal detaches it's self similar copy at some level, after growing up to some level. Growing and detachment should be part of fractional definition.

  • Reply David Carter November 25, 2019 at 7:40 pm

    Downvoted for shameless in video ad when you're already monetized.

  • Reply Spen trav November 25, 2019 at 7:46 pm

    We need a cancer-eating virus.

  • Reply Bigcop80 November 26, 2019 at 1:45 am

    What if we just
    give viruses self replicating genes : hm

  • Reply serendipidus1 November 27, 2019 at 12:28 am

    Can't believe sci show support nord VPN. Gah. Guess we all got to suck somones cock.

  • Reply alentube1 November 27, 2019 at 10:37 pm

    Not only can't viruses reproduce on their own, they don't do much on their own at all. They are more like floating blobs of molecules arranged in a very specific ways that just stay still. Unlike cells which normally have loads of different biochemical processes happening inside.

  • Reply shexdensmore November 28, 2019 at 4:52 am

    Nothing reproduces on it's own, nore does anything produce it's own energy on it's own.

  • Reply usy 09 November 29, 2019 at 3:45 pm

    You can be either dead, alive, or a virus

  • Reply Big Pumper December 2, 2019 at 4:36 am

    Nord vpn got rekt.

  • Reply Dun Mealder December 2, 2019 at 2:44 pm

    so we let the virophages kill off all the viruses then theyll evolve and kill the hosts

  • Reply Nigel Depledge December 3, 2019 at 6:10 pm

    Maybe alive / not alive is a false dichotomy….?

  • Reply Lynxx December 8, 2019 at 8:26 am


  • Reply Topsoil Depletion Awareness (closing the loop) December 11, 2019 at 5:57 pm

    Maybe we evolved from big viruses.

  • Reply Paul Jackson December 13, 2019 at 1:26 pm

    I can't stand these stand-up-comedy science routines. The content fascinates me. The delivery annoys me.

  • Reply Gritos Incoherentes December 15, 2019 at 11:54 pm

    Can they attack reptilians like Mark Zuckerberg and Jeff Bezos?

  • Reply jay23cr December 17, 2019 at 7:16 am

    If it has a genome, it's a form of life trying to pass on it's genes onto offspring, whether they need a host or not in order to reproduce… So yeah, they are a form of life

  • Reply Gizmo December 19, 2019 at 2:43 am

    Internet privacy is a myth… Like unicorns

  • Reply OxyOwO December 19, 2019 at 9:02 pm

    I used the viruses to destroy viruses

  • Reply te0nani January 2, 2020 at 9:55 pm

    Simple question, SciShow: If you use a VPN-Service, guess who gets all your data?

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