Question: How can viruses control their hosts againest their will?

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  1. Dear Nandoslover; Virus has very simple structure, genetic information(DNA or RNA) and coat called capsid. Once virus attach itself to the host and inject its DNA/RNA inside of the host, the host replication machinery doesn’t differentiate its own or foreign invader. It is not something of the host to want to replicate the virus or not. There is no discrimination against the viral genome from the side of the host, Virus take advantage of that blind spot.


  2. awesome question. They’re nasty little critters and I’m amazed that something so small can control our body and even kill us.
    This is a great website, explains it all

    simply said, a virus is not much more than a small particle with some DNA inside. Once inside your body, it will “inject” that virus DNA into your own cell. Then your cell will start to copy the DNA and make more virus particles. We get sick from a virus because of our own immune system trying to get rid of it! So a fever, as you know, increases your body temperature. A higher temperature will often stop processes such as virus reproduction etc.

    Now…..some virusses we can’t fight off and they’ll end up killing us….such as HIV which causes AIDS. They found that HIV virus, once inside your body, produces a protein called VPU. VPU disables your own body’s defense mechanism, so you can’t kill the virus!!


  3. Viruses that control their hosts against their will usually do so by ‘hijacking’ some part of the host. For example, one of the viruses that I study, baculovirus, controls caterpillars by interfering with a specific hormone. Hormones are chemical messengers that the body uses to send signals between cells, and baculovirus deactivates a particular hormone that is responsible for signalling the caterpillar’s moulting. If you’ve never heard of moulting (in insects), it’s the way that many insects shed their exoskeleton when they’ve outgrown them so that they can grow a new, larger one. The virus turns off this moulting hormone and (for some reason that we don’t fully understand) this makes the caterpillar stop feeding and head up to the top of the plant or tree it is on to die.

    All of the viruses that I know of that control behaviour have a specific way of doing it like this. Another example: rabies is a virus that works by controlling its host into become very aggressive and biting other hosts, which is how it spreads. Rabies makes animals aggressive by causing a condition called ‘encephalitis’ when it works its way into the brain. Encephalitis is a swelling of the brain that, when it gets bad enough, causes a whole bunch of symptoms, including aggression and biting (it’s a little like the virus taking a hammer and smashing the brain over and over until it starts to malfunction, like taking a hammer to a car engine). This helps the virus, because while it’s causing swelling in the brain, it has also spread to the saliva glands to that when the animal bites another host the virus is transferred in the saliva.

    Note the similarity between them, though. The virus isn’t sitting up in the brain, pulling strings like a puppet master to make the body dance any way it wants. Instead, viruses that manipulate their hosts find a trick or two that makes the body do what it wants, but it’s always a (relatively speaking) simple change in the host. This shows the process of evolution at work: the virus uses whatever tool it can find to make these changes in the host that help it. It’s nasty, and it’s patchwork, and it’s awesome to study. šŸ™‚


  4. Thats an awesome question Nandoslover & Alutick and Steve has answered it better than I ever could. Rabies is a perfect example of a virus that infects its host in a way that makes sure it has a way of ensuring its own survival – if it didn’t cause its host to become aggressive it wouldn’t have a way of passing itself on.

    The most successful viruses have evolved like rabies has to find the best way to replicate in their host and allow themselves to be passed from host to host (like influenza which is passed from person to person in droplets breathed in when someone sneezes – very effective!).


  5. This has already been really well answered, and I don’t think there is much more that I can add. Viruses are really quite fascinating, in that they don’t require their own machinery, they can just get the host’s cells to do all the work for them. Kind of life walking into a restaurant, telling the waiter what you want, and them making it for you, because it’s not all that different from what they are already doing.