How did viruses come about?
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OK, after reading the answers so far I just have to say who are these people, and where are they getting their information from.  Many are stating that viruses are not considered living.  Well, anybody in the academic circle can tell you it is a matter of opinion, with many arguments for and against (mentioned by others).  I think, however, to answer your question, we should talk about the origins of viruses.\n\nThere is a current thoery out there that the origional viruses were actually defense mechanisms by early organisms against other organisms competing for the same niche. That is, the genes and functions were "excreted" into the environment with the purpose of attaching to something else, specifically, and destroying a host.  Over time, it is believed that evolution allowed the new hosts to survive these infections, yet stay infected, which allowed the nascent genes to become seperated from their origional "makers".  This then led to the viruses being able to evolve independently of the origional organisms.\n\nAs for why they don't have their own kingdom and classification, it is simple.  When the classification system was made, viruses were not known to exist.  Their diseases were, but they themselves were not.  It wasn't until leeweinhook in the 15th century that even bacteria were really discovered.  \n\nSo, as time passed, new organisms were found, and new classes were added to describe them.  The purpose of classification is two fold.  First, it should describe the organism.  Second, it should allow some sense of familial relationship to all other families.  Hence the new areas of prokaryotic, eukaryotic, and archaeobacteria.  \n\nBut with viruses, as others eluded to before, it wasn't certain that they were living at all, so how do we go about classifying them?  One scientist decided that instead of fighting an uphill battle, he would just start his own classification system, completely independent of the ones used for all other life forms. So, believe it or not, viruses are classified into families and genera, but just not placed into the classical naming system.  If you look iti up, you will find that all viruses have a latin name, from phage all the way to plant viruses.  \n\nI hope this helps you out.
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In computer security technology, a virus is a self-replicating program that spreads by inserting copies of itself into other executable code or documents. A computer virus behaves in a way similar to a biological virus, which spreads by inserting itself into living cells. Extending the analogy, the insertion of a virus into the program is termed as an infection, and the infected file (or executable code that is not part of a file) is called a host. \n\nIn the context of computer software, a Trojan horse is a malicious program that is disguised as legitimate software. The term is derived from the classical myth of the Trojan horse. In the siege of Troy, the Greeks left a large wooden horse outside the city. The Trojans were convinced that it was a gift, and moved the horse to a place within the city walls. It turned out that the horse was hollow, containing Greek soldiers who opened the city gates of Troy at night, making it possible for the Greek army to pillage the city. Trojan horse programs work in a similar way: they may look useful or interesting (or at the very least harmless) to an unsuspecting user, but are actually harmful when executed.\n\nA computer worm is a self-replicating computer program, similar to a computer virus. A virus attaches itself to, and becomes part of, another executable program; however, a worm is self-contained and does not need to be part of another program to propagate itself. \n\nhttp://en.wikipedia.org/wiki/Computer_virus
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In computers, a virus is a program or programming code that replicates by being copied or initiating its copying to another program, computer boot sector or document. Viruses can be transmitted as attachments to an e-mail note or in a downloaded file, or be present on a diskette or CD. The immediate source of the e-mail note, downloaded file, or diskette you've received is usually unaware that it contains a virus. Some viruses wreak their effect as soon as their code is executed; other viruses lie dormant until circumstances cause their code to be executed by the computer. Some viruses are benign or playful in intent and effect ("Happy Birthday, Ludwig!") and some can be quite harmful, erasing data or causing your hard disk to require reformatting. A virus that replicates itself by resending itself as an e-mail attachment or as part of a network message is known as a worm.\n\nGenerally, there are three main classes of viruses: \nFile infectors\nSystem or boot-record infectors\nMacro viruses
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all viruses work by taking over the reproductive mechanism of cells and making them manufacture copies of themselves.  Frequently the viral cells put out toxins that cause various illnesses.  "Stomach" viruses do this in the GI tract.
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Last time that happened to me, it was a computer FULL of viruses. It was a computer that belonged to someone else - they had asked me for help. We took it to the computer tech, who said he had never seen so many virus hits on one computer.
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The word is from the Latin virus referring to poison and other noxious things, first loaned into English in 1392. Virulent, from Latin virulentus "poisonous"\nhttp://en.wikipedia.org/wiki/Virus#Etymology
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Viruses must take over an organisms cells to reproduce more viruses. When the cell machinery the virus hijacks to reproduce makes a mistake when making the viruses genetic code (either DNA or RNA depending on the virus) it is called a mutation.\n\nAny time a piece of genetic information gets transcribed incorrectly, or changes due to outside influence (radiation for example) it is called a mutation. Most mutations are harmful, but sometimes a mutation turns out to be beneficial to an organism, or in this case virus which isn't actually alive (that's a whole other question). When it is said that a "virus has mutated" it can mean several things, sometimes it's as simple as a change to the viruses protein shell, called a capsid. Specifically, what scientists are worried about in a H5N1 mutation is a mutation that changes the virus receptor proteins. Receptor proteins are the part of a virus that allows it to attach and attack other cells, these receptors have special shapes, like a key, and only can attach to cells that have a corresponding shape. A good example of this is a Rhino virus, or the common cold, cold viruses have receptor proteins that attack the nasal tissue in humans, which is why it causes that particular type of infection. \n\nMost viruses start out infecting a particular species, the worry with H5N1 is that it will mutate into a form that is easily transmittable between humans, instead of birds. H5N1 appears to be a particularly deadly form of flu, if something like this happened, millions upon millions of people would die. Even countries like the US would be unable to care for all the sick people. This nasty kind of infections happen every once and while, the last really bad one, H1N1, in 1918 killed 50-100 million people.
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viruses cause viral infections, and bacteria cause bacterial infections. But they're also different in other ways.\n\nViruses are much smaller than bacteria.\n\nViruses are not living organism so they need a host.
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it started with chemicals ,followed by ,very simple unicellular things,they worked there way up to amoebas,and it was only a couple of million years to get to bacteria and stuf like coral after that ,then it becomes complicated,\n\nhumans came from out of space i think,they were put here and primitive beings that were already here were maybe genetically improved by those who came from the stars.\n\nas to how humans come ,that is another question
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Viruses are in a nether world. They are neither dead nor alive, and they certainly don't belong to a phylum or a class.
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Essentially the first question is right, but human viruses are very clever in that several coat layers are used. for example HPV, HSV (herpes).  Viruses are just proteins and DNA, nothing more.  They don't contain organelles, they don't reproduce independantly, they don't fulfill many life functions.
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Thank you for warning everyone about this. Personally, I think viruses are for good use only when put in the hands of the military. That way, the evil people will get the virus. I seriously wouldn't want that virus, especially with my "Proof that God exists" on my computer.
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the doctor was partially right, for some viruses. many diseases we get from mutations in bacteria or viruses, from animals, from food, from a new environment we aren't used to, etc.\n\np.s. Any expert can tell you exactly how to contract the bubonic plague (often called the black death, the black plague, the plague, etc.) that wiped out 1/4 of Europe in its time. People got it from fleas. It is often associated with rats because rats carry fleas, and therefore the plague. When the flea bit an infected person, and then someone else the other person got infected, as did anything else the flea bit. And with the poor sanitation a few hundred years ago, and their total lack of knowledge as to what caused it, it is no wonder the plague wiped out entire towns.
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It is True that anti-virus companies develop their own virus and provide patches for it and some really click very well such as the KAMASUTRA virus..It was a home grown virus by some company..There is a collection of some anti-viruses in this page-www.varunhacker.tk..Hope u are satisfied with the answer.
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Viruses are said to be both living and non-living because it is simply a matter of opinion. Scientists can't really agree as to what viruses really are, (they don't belong to any of the five kingdoms you know!).\nSome people say that they are non-living because they aren't cells and don't metabolise, they are merely a bundle of DNA or RNA in a protein capsid.\nHowever they must survive, thus they invade other cells and use the cell to replicate their own genetic material. So the fact that they reproduce (even in the simplest way) has caused other scientists to regard them as living.\nThis duality is unique to viruses (as far as I know!) and is a sign of a primitive organism not an evolved one.\nThink about it, if something is so siple people don't know whether it is alive or dead it can't be very evolved
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I don't know how viruses work. I guess it is possible but wait for the other answers. People do horrible things these days with computers.
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The probably multiple origins of viruses are lost in a sea of conjecture and speculation, which results mostly from their nature: no-one has ever detected a fossil virus as a particle; they are too small and probably too fragile to have withstood the kinds of processes that led to fossilisation, or even to preservation of short stretches of nucleic acid sequences in leaf tissues or insects in amber. \n\nAs a result, we are limited to studying viruses that are isolated in the present, or from material that is at most a few decades old. The new science (or art) of virus molecular systematics is, however, shedding a great deal of light on the distant relationships of, and in some cases on the presumed origins of, many important groups of viruses.  This is as a result of the sequencing of all or part of the genomes of representatives of many of the known varieties of viruses, including the largest (pox- and herpesviruses) and the smallest (gemini- and other ssDNA viruses).  If viral genomes are compared with each other and with cellular sequences, presumed patterns of evolution / divergence of the genomes can be reconstructed.\n\nGeminiviridae, for example, are a diverse group of viruses - with different genera having different numbers of genes and genome components - that presumably have a common origin - and one that may be traceable back to beyond 200 Myr BP, if one takes into account geographical diversity, and genetic divergence of vectors and of plant hosts (see Rybicki, 1994).   Divergence of these viruses is illustrated here.\n\nPotyviridae are also a putatively ancient family of viruses, with genera that have different numbers of genome components and whose gene pool is not shared by all members: a representative coat protein tree is shown here.  Bymoviruses have two genome components and are fungus-transmitted; all the rest have a single genome component.  Potyviruses are aphid-transmitted; rymo- and triticiviruses are mite-transmitted, and ipomoviruses are whitefly-transmitted.  They are supposed to descend from a fungal virus, probably over 200 Myr ago (AJ Gibbs, pers. comm.).\n\nIf one were to go far back into evolutionary time, a case could be made for descent from a single ancestor of at least the replicase-associated functions of all viruses with positive-sense and negative-sense single-strand RNA genomes; likewise, large DNA viruses like pox- and herpesviruses and Phycodnaviridae could be presumed to have "degenerated" (if one believes viruses to be degenerate organisms, which I for one do not...) from cellular organisms, given that their enzymes share more sequence similarity with sequences from cells than with other viruses or anything else. \n\nRetroviruses, pararetroviruses, retrotransposons and retroposons all probably share a common origin of the reverse transcription function, which in turn may be a living relic of the enzyme that enabled the switch from a presumably RNA-based genetics to DNA-based heredity. \n\nThe main message to come from "deep" phylogenetic studies is that early virus evolution was almost certainly modular: that is, that certain "core modules" that proved to be successful - like the retrovirus pol gene, and the picornavirus-like protease-Vpg-polymerase module - appear in a number of different contexts.   Thus, certain animal viruses - like picornaviruses and alphaviruses - have relatives among plant viruses which do not necessarily share the same morphology, number of genome components, or even genome organisation or number of genes. \n\nFor example, small spherical picornaviruses (ssRNA, 1 component, infect animals) are related to comoviruses (small spherical, 2 component, plant) and Potyviridae (filamentous, 1 or two genome components, plant), as part of a "Picorna-like Supergroup". Similarly, Sindbis (ssRNA, enveloped spherical, single RNA, animals) virus is related to Bromoviridae (naked spherical, 3 component, plant) and Tobamoviruses (naked