What is a virus?

28 July 2004

Viruses are distinct biological entities with the following properties:

1. A virus is an infectious, obligate intracellular parasite.

2. The genetic material of a virus is either DNA or RNA.

3. The genetic material of a virus enters a host cell and directs the production of the building blocks of new virus particles (called virions).

4. New virions are made in the host cell by assembly of these building blocks.

5. The new virions produced in a host cell then transport the viral genetic material to another host cell or organism to carry out another round of infection.

Viruses are easy to understand when we reduce their properties to simple descriptions such as those listed above. The confounding issues lie in the details – and with viruses, there are many, many details.

  • Slopez

    The word virus comes from the Latin for a poisonous liquid. Virus are vesicles produced by a cell capable of carrying genetic codes and cellular material to other cells. The absorption of this material into a recipient is commonly called infection although it is not necessarily harmful. Virus produced by healthy cells are called passenger virus. Virus produced by poisonous cells are called pathogenic virus.There is strong evidence that polio was not eradicated by vaccination but by banning the use of DDT.

  • Slopez

    The word virus comes from the Latin for a poisonous liquid. Virus are vesicles produced by a cell capable of carrying genetic codes and cellular material to other cells. The absorption of this material into a recipient is commonly called infection although it is not necessarily harmful. Virus produced by healthy cells are called passenger virus. Virus produced by poisonous cells are called pathogenic virus.There is strong evidence that polio was not eradicated by vaccination but by banning the use of DDT.

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  • Mbeaving

    Baning DDT? That's completely nonsensical and does not explain historical and current instances of polio without DDT. Sound quite pseudosciency.

  • JRobertson

    I have to agree with Mbeaving. Simply imposing a ban on DDT is hardly the answer for polio eradication. Most likely it is due to the vaccines that were prescribed to children during the mid- twentieth century. If anyone is interested, I have posted some information relating to the virology of the common adenovirus infection here: http://adenovirus.com/adenovirus-virology.html

  • Roberta R

    There is nothing pseudosciency about environmental contaminants such as arsenic or DDT  turning the polio virus into a paralytic agent.  What is pseudosciency is the claim that polio spread as a consequence of increased sanitation,  a claim still made by  some in the medical establishment. 

  • Crawford

    Wow, didn’t expect this. Maybe in addition to science individuals should learn the characteristics of fallacy and propaganda, or should I say advertising. The first sentence answers the question. Define “biological entity”. The itemized list is of descriptive characteristic factors. To throw another option. The UK is devolving, by having governmental representative power devolved to Scotland, Wales, Northern Ireland and England. This is in some wayva way to make the constituant parts survive better and be more functional. Are viruses, mycoplasma and prions devolved or simplified bacteria? Did they occur as survival options?

  • http://www.facebook.com/profile.php?id=1643463430 Wyatt Henderson

    DDT was a chemical. A solid chrystalline. Viruses are a series of molecular packages that are interpreted and copied by a host cell. DDT is incapable of causing polio because it is a chemical, not a virus. Polio is caused by a virus, the poliovirus, and the DDT compound is not capable of inhibiting, prohibiting, or otherwise altering the poliovirus itself, because they are on completely separate molecular levels. Chemicals can’t make viruses, but they can mimic the SYMPTOMS of one.

  • http://www.facebook.com/profile.php?id=1643463430 Wyatt Henderson

    I don’t think that DDT caused the poliovirus to take on the paralytic characteristic, because poliovirus has been known and recorded over centuries. It has always possessed the paralytic characteristic. It was not known, of course, that it was all the same virus then, but we have since isolated it and know that it was indeed the poliovirus.

  • Deborah L.

    I can tell you what a virus is not. A one celled vegetable micro-organism found nearly every where!

  • Jaci Lapointe

    Thank you for giving a simple and concise description of a virus and what it does. I am in the process of both learning (Virology I: Welcome to Virology) and of also teaching my 5 and 9 year old kids about viruses. This list gave me a really easy way to show how viruses work, using a building site as an example (they like construction) basically that the virus comes in and changes the building “plans” and than teaches the builders it’s plans and sends them out to change neighboring building plans. The look of realization dawned on their little faces, it was great!! THANKS… I know my version for my kids was over simplified but it works for their age!

  • SoloPocono

    I can remember my kids-a little younger-fascinated with the bio/micro/virology classes & labs I had. They were the “mascots” of my pre-med class and my professors would occasionally allow them to “participate”. My son would draw pictures of “streptococci” and VHD (Ebola) in his 1st grade classes instead of houses and animals, lol! His teachers weren’t sure what to make of him! My daughter, was interested, but not like my Son.
    My daughter is now an RN/Paramedic and going into Pre-med, my Son into Foreign Relations and politics….go figure.. ;)

  • Jaci Lapointe

    :) my son is into both science and photography and my daughter into science and punk music… who knows where it might lead!

  • Austin White

    Reading this article in detail gave me a clearer reason why viruses undergo replication..No. 5 up there explains it…(For continiuety of their existence)

  • unclealfie

    What evidence is that?

  • unclealfie

    Do you really think it’s that simple? What do you think you mean by “completely separate” molecular levels? That’s simply science-babble with no meaning. Chemicals can most certainly infect and affect the way virus particles and manufactured, transcribed, replicated and assembled in a host cell in any number of ways.

  • jj

    The word virus comes from the Latin for a poisonous liquid. Virus are vesicles produced by a cell capable of carrying genetic codes and cellular material to other cells. The absorption of this material into a recipient is commonly called infection although it is not necessarily harmful. Virus produced by healthy cells are called passenger virus. Virus produced by poisonous cells are called pathogenic virus.There is strong evidence that polio was not eradicated by vaccination but by banning the use of DDT.