What is Virus: Definition and 148 Discussions

A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all types of life forms, from animals and plants to microorganisms, including bacteria and archaea.
Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 9,000 virus species have been described in detail of the millions of types of viruses in the environment. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. The study of viruses is known as virology, a subspeciality of microbiology.
When infected, a host cell is forced to rapidly produce thousands of copies of the original virus. When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles, or virions, consisting of (i) the genetic material, i.e., long molecules of DNA or RNA that encode the structure of the proteins by which the virus acts; (ii) a protein coat, the capsid, which surrounds and protects the genetic material; and in some cases (iii) an outside envelope of lipids. The shapes of these virus particles range from simple helical and icosahedral forms to more complex structures. Most virus species have virions too small to be seen with an optical microscope, as they are one-hundredth the size of most bacteria.
The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction. Viruses are considered by some biologists to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, although they lack the key characteristics, such as cell structure, that are generally considered necessary criteria for life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life", and as self-replicators.Viruses spread in many ways. One transmission pathway is through disease-bearing organisms known as vectors: for example, viruses are often transmitted from plant to plant by insects that feed on plant sap, such as aphids; and viruses in animals can be carried by blood-sucking insects. Influenza viruses are spread by coughing and sneezing. Norovirus and rotavirus, common causes of viral gastroenteritis, are transmitted by the faecal–oral route, passed by hand-to-mouth contact or in food or water. The infectious dose of norovirus required to produce infection in humans is less than 100 particles. HIV is one of several viruses transmitted through sexual contact and by exposure to infected blood. The variety of host cells that a virus can infect is called its "host range". This can be narrow, meaning a virus is capable of infecting few species, or broad, meaning it is capable of infecting many.Viral infections in animals provoke an immune response that usually eliminates the infecting virus. Immune responses can also be produced by vaccines, which confer an artificially acquired immunity to the specific viral infection. Some viruses, including those that cause AIDS, HPV infection, and viral hepatitis, evade these immune responses and result in chronic infections. Several antiviral drugs have been developed.

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  1. T

    More on COVID and Wuhan

    A New York Times article about the current controversy over origin of the COVID-19 virus. Titled: The Government Must Say What It Knows About Covid’s Origins Wide ranging but somewhat superficial, it does have about 15 links to references embedded in it though...
  2. A

    Virus mutation by artificially guided selection

    I came across an article on CNN on a bunch of scientists researching the dangers of very old viruses that have been "paused" within the northern permafrost and their prospects of causing infection due to their release which might happen as the permafrost decreases...
  3. T

    Medical Universal Virus? - mononucleosis, chronic fatigue, multiple sclerosis....

    forget about chronic fatigue, I remembered it has been tracked to gut bacteria! Epstein-Barr virus seems to be associated with many conditions. "Associated" is the operative there because almost everyone is a host for Epstein-Barr. Science News has a somewhat long but quite readable article...
  4. W

    Getting a Phony Virus Warning as I Write This

    Hi, I'm getting a warning message that is spoofing my Windows Defender and McCaffee. In my Internet settings, I have blocked popups, yet the message below
  5. Astronuc

    Powassan virus on the rise in the US?

    https://www.caryinstitute.org/news-insights/media-coverage/lethal-tick-borne-disease-spreading-us-driven-climate-change Certainly ticks have been a major problem in the NE US with respect to Lyme disease, Ehrlichiosis, and Babesiosis, and now we have Powassan virus to add to the list of...
  6. Astronuc

    Tanzania, Deadly outbreak, unknown disease (Ebola-like, hemorrhagic virus?)

    https://abcnews.go.com/International/tanzania-investigates-deadly-outbreak-mystery-disease/story?id=86870310 https://www.ndtv.com/world-news/mysterious-ebola-like-disease-kills-3-in-tanzania-probe-launched-3158007 The outbreak in Tanzania comes days after Ghana reported two suspected cases of...
  7. Astronuc

    Origin of SARS-Cov-2 virus

    Striking new evidence points to seafood market in Wuhan as pandemic origin point Two claims in the article: Live animals that are susceptible to COVID-19 were in the market in December 2019 Live susceptible animals were held in a stall where SARS-CoV-2 was later detected on a machine that...
  8. PeroK

    Insights Probabilistic Factors Involved in Disease and Virus Testing

    Continue reading...
  9. S

    "Dormant" virus, chicken pox, Shingles, vaccination - confused

    I tried a web search but how this immunity stuff works with chicken pox, shingles, and the vaccination I cannot understand. Person can suffer chicken pox infection from the virus, recover, and later be vaccinated (at least age 50) with Shingrix vaccination, to be protected. But the virus is...
  10. jim mcnamara

    Multiple Sclerosis and Epstein-Barr virus infection

    Statnews article: https://www.statnews.com/2022/01/13/strong-new-evidence-suggests-virus-triggers-multiple-sclerosis/ Evidence from a colossal blood bank at Walter Reed Army Hospital allowed researchers to look over a long time span of samples for a huge number of US service men/women. The...
  11. jim mcnamara

    Bat wild virus -very close match to SARS-Cov2-19

    Paper, accepted during editing into researchsquare.com, part of nature.com. https://www.researchsquare.com/article/rs-871965/v1 Two species of bats in Laos had Corona viruses very close to the SARS-Cov2-19 virus. Closer than any other virus found. They infect human cells via ACE2, in...
  12. Sagittarius A-Star

    COVID Electric field of moderate strength inactivates Covid-19 virus

    A science team from the university of Kassel (Germany) proved with a physical model, that a moderate electric field inactivates the Convid-19 virus. Source: https://www.nature.com/articles/s41467-021-25478-7 via...
  13. E

    COVID Do virus masks actually work?

    Do virus masks have any effect on preventing or reducing risk of infection from CV19? Have there been any studies on this?
  14. BillTre

    Unusual Virus Niche Discovered in 2009

    I just found this, but it was published in 2009. A "virus" is described (guessing this is sadly behind a paywall) that is so weird that its not clear it should be classified as a virus. Most of what would be their normal genome has been incorporated into the genome of a parasitic wasp. These...
  15. A

    COVID Weak or non immunity after virus or vaccine

    How can it be that some people develop next to no immunity , cell memory after a Covid infection or vaccination? Immunity develops after the body sees and fights off foreign protein aka virus presenting within the body, so whichever has gotten infected with the virus has to undergo these steps...
  16. B

    COVID China should give reparations to the world for spreading Corona virus

    I firmly believe China should give financial reparations to the world for creating and spreading Corona virus.
  17. T

    COVID Common Cold Virus Suppresses COVID-19

    I'll trade a cold for Covid-19 any time! https://www.medicalnewstoday.com/articles/a-common-cold-virus-may-help-fight-covid-19 Cheers, Tom
  18. jim mcnamara

    How to create a virus that completely evades vaccine

    Paul Biensiasz is a virologist at Rockefeller Medical, he authored this on twitter, titled "musings of a pissed virologist"
  19. Rongeet Banerjee

    Internal Structure of SARS-CoV-2 virus

    Homework Statement:: Does Sars-cov-2 Virus have Reverse Transcriptase enzyme for its replication purpose? Relevant Equations:: None I surfed Google for a relevant answer to my query but failed to find one.I just want to confirm whether Sars-cov-2 has the Reverse Transcriptase or...
  20. C

    COVID The Evolution of the SARS-COV-2 virus

    The sudden appearance of SARS-COV-2 as a virulent pathogen in humans raises the question of how it gained the ability to attack human cells and why it is highly contagious. If I understand this right, an article in Virology Blog...
  21. Delta2

    Medical What makes it so hard to find a cure for the Corona virus?

    Corona has come and it doesn't seem to go away that easily. Why can't modern science find some cure that will prevent so many deaths? Why for example we can't find an antibiotic for this specific virus? What about other approaches(vaccine)? I just wish a cure could be found so we may continue...
  22. E

    Can Virus Masks Lower Flu Cases This Year?

    Could this year's flu season be used to determine the effectiveness of virus masks? Every other person if wearing one, so if flu cases are significantly less than normal, that means that virus masks are having a noticeable effect?
  23. BillTre

    Gorgeous Corona Virus Images

    Here is a Carl Zimmer article in the NY Times showing some fantastic images of the corona virus. These are mostly computer generated images (pretty common these days) based on cryo-EM (Electron Microscopy) and biochemical/molecular biology type data. They are very well rendered, down to the...
  24. bhobba

    COVID Supercomputer Analysis Of Covid Virus

    Hi All Someone passed onto me the following supercomputer analysis of the Covid virus: https://elemental.medium.com/a-supercomputer-analyzed-covid-19-and-an-interesting-new-theory-has-emerged-31cb8eba9d63 Very interesting. Thanks Bill
  25. Evo

    Corona virus, no longer considered just a respiratory disease

    This has come up in the press the last few days that they now believe Covid-19 is not just a respiratory disease. This is a very interesting article on it. It explains the virus and how it works. https://www.ucsf.edu/magazine/covid-body
  26. M

    Is isopropyl alcohol safe?

    I bought a can of soft drink and was wondering whether I should spray 100% isopropyl on it before putting my mouth on it to drink. I did spray and it smelt bad but I wiped it off and drank the can. Is that unsafe or is it the opposite, safer than drinking without spraying? Would it kill corona...
  27. mktsgm

    Quantum of cells directly infected by a virus?

    In any viral infection, we know that an invading virus enters the cell and damages them (cytolytic/cytopathic). This may be a starting point for inflammation down the road. Though initial inflammation may be beneficial, a longer than necessary inflammatory process proves more damaging than...
  28. A

    Artificial virus stimulation/fabrication, what is our current state?

    I've been thinking about this but now especially with regards to Covid-19 there are a lot of theories out there starting from absolute fringe and lunacy to somewhat scientific and even ones with sources to academia. For starters not to get too long my question is, What is our current known...
  29. J

    Medical Losing immunity to a virus

    I once read that just because a virus mutates doesn't mean you lose immunity to it. I do not know much biology, but could one of you please explain how that is possible?
  30. V

    How does virus infection work?

    What is the probability that a healthy person with fully functional immunity will become infected when he receives a tiny amount of some (flu kind) virus on a) hands, b) eyes, c) lungs? I don't know how to define a small dose of a virus, but I guess if only one virus gets in my lungs, my immune...
  31. C

    Virus and Zombies (Resident Evil and ?)

    Covid-19 affects mainly the elderly so the results are partial lockdown and many youth still swimming at Miami Beach. And the elderly victims are drowning at ICUs even with ventilators. In Contagion. The virus affectedthe brain instead of the lungs and the result was encephalitis (infection of...
  32. mktsgm

    Medical Do the viruses damage our cells directly?

    Viruses when they infect us, enter the target cells, hijack the machinery and start producing their own Copy and eject out. So what? Question is, how do they directly cause injury to our cells? Do they harm injury our cells directly? Of course we know that our own immune system which becomes...
  33. P

    Is the Coronavirus Primarily a Human Virus?

    I keep wondering why we do not know more about the virus? How hard is it to expose some mice to Coronavirus and see what happens? Then I considered that perhaps the virus is primarily a human virus and does not effect other life forms like lab mice. There have been cases with dogs and the...
  34. afcsimoes

    Questions about the Corona virus

    1. are there H2O molecules inside a Corona vírus? If yes, drying the virus kills it? 2. the lipid external layer of the Corona virus acts as a glue that attach the virus to any surface? 3. how much time a Corona vírus survives in the dry air? and in a dry surface?
  35. B

    Is hydrogen peroxide effective against the corona virus?

    If oxygen is effective against bacteria virus and cancer why isn't it used against coved-19? DMSO is known to bond with certain substances and could carry HP into the blood stream and kill off COVID-19.
  36. S

    Immunity from exposure to similar virus strains?

    The summary says it all. But to give an example, imagine a mild virus that has gone the rounds of Region A. Later it makes its way to Region B, and immediately mutates into a more rapidly spreading strain that puts B's inhabitants at great risk. Now that new strain travels back to Region A...
  37. A

    COVID Covid-19 virus disinfectant question -- Any aerosol options?

    I have a question both with regards to the current virus as well as to other potential diseases that are carried around in aerosol form, I have seen that commonly all hand sanitizers or sanitizers in general that use substances that are safe to humans use alcohol in some form. So I would presume...
  38. E

    B Predator-prey model of a virus

    I was trying to put together a basic mathematical model for the Coronavirus and happened to stumble across the predator prey model; if ##x## is the number of humans and ##y## is the number of Covid-19 viruses, then $$\frac{dx}{dt} = ax-bxy$$ and $$\frac{dy}{dt} = cxy - dy$$ I took the reciprocal...
  39. pinball1970

    New virus reported from Brazil

    Name Yaravirus found in an artificial lake with 90% novel genes. Evolution significance?
  40. mktsgm

    Medical Virus Reproduction: Understanding the Paradox

    Science believes that a virus does not have life. They do not display any of the properties of 'life' such as homeostasis - they lack, growth - they don't grow, response to stimuli - they don't respond etc. i.e., They're not as alive as bacteria, animals, humans. If so, how come they want to...
  41. Y

    Is mapsnow.co a Virus? Safety Guide & Apt Info

    I installed mapsnow.co on my computer, is that a virus or just an apt?
  42. BillTre

    Anti-Cancer Virus Treatment

    This Science News article reports that researchers using a modified adenovirus (that normally causes mild respiratory infections) that only grows in retinoblastoma tumor cells, researchers were able to improve upon (but apparently not cure) the results of cancer drugs in rabbits and mice. Trials...
  43. G

    I Send the measurement device through a double slit

    Hi. Double slit experiments are being performed successfully with increasingly large molecules. Some physicists (e.g. Anton Zeilinger) believe it might work with viruses as well. Assuming it works with a system that qualifies as a measurement device (be it a virus or something else complex...
  44. Suyash Singh

    Google chrome virus

    I noticed this widespread adware infecting chrome on nearly all devices. For a few days though i have noticed that on all the devices when the spam sites are opened by that virus they close immediately. Is it that chrome got to know about it and has defeated it? But why is the virus still...
  45. Greg Bernhardt

    Our memory comes from an ancient virus

    Pop science: http://bigthink.com/philip-perry/our-memory-comes-from-an-ancient-virus-neuroscientists-say Paper: http://www.cell.com/cell/fulltext/S0092-8674(17)31504-0
  46. Y

    Watch out for some articles on Yahoo (virus?)

    I just want to let you know what I suspect I got the virus from. I don't serve on questionable sites, no porn sites or anything close to like that. I read articles on Yahoo front page. Lately ( last year), they start to have articles like "How's you favorite tv stars from the 80s look like now"...
  47. Y

    Can a virus be in a memory stick?

    Can virus infect memory stick? I backed up my files onto the memory stick from my infected laptop. Can virus get copied into the memory stick? Can virus infect pdf, jpg, doxx or other files? How can I scan the memory stick without worry about infecting another computer that try to scan the...
  48. jedishrfu

    June 2017 Petya Ransomware Virus Hits Ukraine

    This new virus used multiple means of attack to infect machines on a network. The initial attack came from a legitimate software updater program: http://www.zdnet.com/article/microsoft-petya-ransomware-attacks-were-spread-by-hacked-software-updater/
  49. Drakkith

    Possible Virus on my PC

    A few days ago my AVG antivirus detected a virus and successfully eliminated it. Since then I've been having an issue where a window will briefly popup but is immediately closed. I'm concerned that the virus wasn't cleared fully or that I've gotten another virus, but I've done several full scans...
  50. M

    Probability virus question at different infection rates

    Homework Statement From various studies, it is known that once an individual is infected with a virus, they become infectious at rate λ. The individual will recover at rate λ, independent of the time it took for them to become infectious. Let X be the total amount of time an individual has this...