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view · edit Frequently asked questions Q1: Are viruses alive? A1: Opinions differ on whether viruses are a form of life, or organic structures that interact with living organisms. They have been described as "organisms at the edge of life",[1] since they resemble organisms in that they possess genes and evolve by natural selection,[2] and reproduce by creating multiple copies of themselves through self-assembly. However, although they have genes, they do not have a cellular structure, which is often seen as the basic unit of life. Additionally, viruses do not have their own metabolism, and require a host cell to make new products. They therefore cannot reproduce outside a host cell (although bacterial species such as rickettsia and chlamydia are considered living organisms despite the same limitation). Accepted forms of life use cell division to reproduce, whereas viruses spontaneously assemble within cells, which is analogous to the autonomous growth of crystals. Virus self-assembly within host cells has implications for the study of the origin of life, as it lends further credence to the hypothesis that life could have started as self-assembling organic molecules.[3] ^ Rybicki EP (1990) "The classification of organisms at the edge of life, or problems with virus systematics." S Aft J Sci 86:182–186 ^ Holmes EC (October 2007). "Viral evolution in the genomic age". PLoS Biol. 5 (10): e278. doi:10.1371/journal.pbio.0050278. PMC 1994994. PMID 17914905. Retrieved 2008-09-13.{{cite journal}}: CS1 maint: unflagged free DOI (link) ^ Koonin EV, Senkevich TG, Dolja VV (2006). "The ancient Virus World and evolution of cells". Biol. Direct. 1: 29. doi:10.1186/1745-6150-1-29. PMC 1594570. PMID 16984643. Retrieved 2008-09-14.{{cite journal}}: CS1 maint: unflagged free DOI (link)

	Introduction to viruses is a featured article; it (or a previous version of it) has been identified as one of the best articles produced by the Wikipedia community. Even so, if you can update or improve it, please do so.
	This article appeared on Wikipedia's Main Page as Today's featured article on October 21, 2012, and on March 27, 2020.
Article milestones Date Process Result December 6, 2007 Articles for deletion Speedily kept December 21, 2007 Peer review Reviewed March 18, 2008 Good article nominee Listed June 28, 2008 Peer review Reviewed July 12, 2008 Featured article candidate Promoted March 11, 2009 Articles for deletion Speedily kept Current status: Featured article

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As an intelligent, non scientific adult who is keen to better understand this pandemic, I'm grateful to all of you -- writers, editors - who have developed this article. Plain language intended for non-scientists is exactly what we need. Too many scientific Wikipedia articles are written by scientists for scientists - and continue to mystify the masses. THank you,thank you, thank you. — Preceding unsigned comment added by 2607:FEA8:BEA0:D640:B036:6B5:AF34:D50 (talk) 10:50, 11 May 2020 (UTC)[reply]

Thanks for the feedback. It is much appreciated. Graham Beards (talk) 20:40, 11 May 2020 (UTC)[reply]

it's not often someone provides such positive feedback, thank you very much. Read-write-services (talk) 12:49, 10 August 2021 (UTC)[reply]

Is there a difference between viruses and bacteria for whether infection is typically local or systemic? When we get a cut on our skin, we are concerned about a bacterial infection, not a viral one. We can treat such an infection by locally applying antiseptic or even by lopping off a gangrenous foot. The only such viral skin infection I can think of are warts. Even viruses that cause symptoms on the skin (herpes viruses like cold sores or chicken pox) appear to infect us more deeply than that. I can see that some viral infections that cause diarrhoea replicate in the gut, and those that cause chest infections replicate in our lungs. Both are internal epithelial cells. But are there any others that replicate in the skin, or remain tightly localised in the body? The Infection#Bacterial or viral repeats this ideal that viruses are more commonly systemic than bacterial infections. Why should that be? -- Colin°^Talk 15:39, 8 November 2021 (UTC)[reply]

Some viral infections, such as warts are localised. Other ones that seem to be confined sites on the skin include human herpesvirus 8 (HHV-8) which causes Kaposi's sarcoma, cold sores and genital herpes virus infections, orf virus and molluscum contagiosum. Diarrhoea viruses, such as rotavirus, astrovirus, norovirus seem to be confined to the gut - at least with regard to their replication. Epstein-Barr virus is confined to a subgroup of lymphocyctes and HIV virus to cells which have the CD4 receptor. Most viruses can cause a viraemia (be found in the blood) but this does not mean they reproduce there. It's all about the receptors on the cells; rotaviruses attach to the cell through sialic acid containing receptors. Infections are localised when cells with appropriate receptors are only found locally in certain tissues. Hepatitis viruses reproduce in liver cells because these cells have the right receptors - but they do cause a viraemia. Many viruses can get into the blood without directly causing any harm there (as opposed to in the tissues). Although some bacteria can give rise to asymptomatic bacteraemia (in other words can be recovered from blood cultures), generally unlike viruses, bacteria in the blood is bad news because they reproduce outside cells. --Graham Beards (talk) 16:06, 8 November 2021 (UTC)[reply]

Graham Beards, MOS:PAGERANGE changed sometime in the years I wasn't paying attention, so I've fixed my damage here. Could you check these page ranges, as I'm concerned whether there is a typo:

• Collier, Balows & Sussman 1998, pp. 11–21
• Collier, Balows & Sussman 1998, p. 11
• Collier, Balows & Sussman 1998, pp. 11–12

Is the first supposed to be 11 to 21, or is 21 transposed from 12? SandyGeorgia (Talk) 17:06, 22 March 2022 (UTC)[reply]

It is correct. Pages 11 to 21 all cover The Origin and Evolution of Viruses. Possible parasitic origins are on page 11 and plasmids are on pages 11 to 12. I really need to update that source but not because any of the theories have changed. Graham Beards (talk) 18:26, 22 March 2022 (UTC)[reply]

Thanks for checking; was worried I had made one of my many typos somewhere back in the history, SandyGeorgia (Talk) 18:29, 22 March 2022 (UTC)[reply]

would this article be more appropriate for https://en.wikiversity.org more than Wikipedia? Wikiversity is also a Wikimedia project.... limitless peace. Michael Ten (talk) 13:34, 18 October 2022 (UTC)[reply]

Hi, are you saying it is not appropriate here? Graham Beards (talk) 13:40, 18 October 2022 (UTC)[reply]

In the lead, second to last paragraph, one can read:

"Viruses, especially those made of RNA, can..."

Is this to mean that the whole virus is actually made of RNA, or just its genes? Since the lead stated earlier that their genes are built from either DNA or RNA, I would guess the latter, in which case I would suggest clarifying this. For example:

"Viruses, especially those with genes made of RNA, can..." Ribidag (talk) 09:13, 4 March 2023 (UTC)[reply]

• Yes, but this is an introductory article. Best to keep the Lead simple.Graham Beards (talk) 09:30, 4 March 2023 (UTC)[reply]