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==== Objects and surfaces ====
==== Objects and surfaces ====
[[File:Door Handle.JPG|alt=A silver-colored door handle on a white door|thumb|Surfaces that are often touched such as [[Door handle|door handles]] may transmit COVID-19, although is not thought to be the main way the virus spreads.]]
It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it (called a [[fomite]]), and then touching their own mouth, nose, or possibly their eyes - although this has not yet been been documented.<ref name="WHOTransBrief" /><ref name="ECDCTRANSMIT" /> This is not thought to be the main way the virus spreads.<ref name=":4" /><ref name="ECDCQA" /><ref name=":9" /> On surfaces the amount of viable active virus decreases over time until it can no longer cause infection. One study indicated that the virus can be detected for up to four hours on copper, up to one day on cardboard, and up to three days on plastic ([[polypropylene]]) and stainless steel ([[SAE 304 stainless steel|AISI 304]]).<ref name="ECDCQA" /><ref name="StableNIH">{{cite web|url=https://www.nih.gov/news-events/news-releases/new-coronavirus-stable-hours-surfaces|title=New coronavirus stable for hours on surfaces|date=17 March 2020|publisher=[[National Institutes of Health]]|url-status=live|archive-url=https://web.archive.org/web/20200323032520/https://www.nih.gov/news-events/news-releases/new-coronavirus-stable-hours-surfaces|archive-date=23 March 2020|access-date=30 April 2020}}</ref><!-- Quote: The scientists found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detectable in aerosols for up to three hours, up to four hours on copper, up to twenty-four hours on cardboard and up to two to three days on plastic and stainless steel. --><ref name="Doremalen">{{cite journal |vauthors=van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, Tamin A, Harcourt JL, Thornburg NJ, Gerber SI, Lloyd-Smith JO, de Wit E, Munster VJ |display-authors=6 |title=Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 |journal=New England Journal of Medicine |volume=382 |issue=16 |pages=1564–1567 |date=April 2020 |pmid=32182409 |pmc=7121658 |doi=10.1056/NEJMc2004973 |doi-access=free}}</ref> There
It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it (called a [[fomite]]), and then touching their own mouth, nose, or possibly their eyes - although this has not yet been been documented.<ref name="WHOTransBrief" /><ref name="ECDCTRANSMIT" /> This is not thought to be the main way the virus spreads.<ref name=":4" /><ref name="ECDCQA" /><ref name=":9" /> On surfaces the amount of viable active virus decreases over time until it can no longer cause infection. One study indicated that the virus can be detected for up to four hours on copper, up to one day on cardboard, and up to three days on plastic ([[polypropylene]]) and stainless steel ([[SAE 304 stainless steel|AISI 304]]).<ref name="ECDCQA" /><ref name="StableNIH">{{cite web|url=https://www.nih.gov/news-events/news-releases/new-coronavirus-stable-hours-surfaces|title=New coronavirus stable for hours on surfaces|date=17 March 2020|publisher=[[National Institutes of Health]]|url-status=live|archive-url=https://web.archive.org/web/20200323032520/https://www.nih.gov/news-events/news-releases/new-coronavirus-stable-hours-surfaces|archive-date=23 March 2020|access-date=30 April 2020}}</ref><!-- Quote: The scientists found that severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was detectable in aerosols for up to three hours, up to four hours on copper, up to twenty-four hours on cardboard and up to two to three days on plastic and stainless steel. --><ref name="Doremalen">{{cite journal |vauthors=van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, Tamin A, Harcourt JL, Thornburg NJ, Gerber SI, Lloyd-Smith JO, de Wit E, Munster VJ |display-authors=6 |title=Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1 |journal=New England Journal of Medicine |volume=382 |issue=16 |pages=1564–1567 |date=April 2020 |pmid=32182409 |pmc=7121658 |doi=10.1056/NEJMc2004973 |doi-access=free}}</ref> There


Revision as of 09:28, 6 October 2020

COVID-19 is a new disease, and how it spreads remains under investigation.[1][2] It spreads from person to person, most often when they are physically close,[a] but sometimes over longer distances, especially indoors.[1][4] When an infected person breathes, coughs, sneezes, talks or sings, they produce contaminated droplets and aerosols.[1][4] These travel through the air, usually over short distances, but some can remain suspended in the air, to infect other people who inhale them.[5][1][4] The closer people interact, and the longer they interact, the more likely the virus is to transmit.[1]

It transmits very easily and sustainably, however the number of people generally infected by one infected person varies.[5][1] It is more infectious than influenza, but less so than measles.[4][1] It can transmit when people are symptomatic, for up to two days prior to developing symptoms, and even if a person never shows symptoms (asymptomatic transmission - it is unclear how often this happens).[1][2] A July 2020 systematic review found that the proportion of asymptomatic cases ranges from 6% to 41%.[6] People remain infectious in moderate cases for 7–12 days, and up to two weeks in severe cases.[4]

It often spreads in clusters, where infections can be traced back to an index case or geographical location.[7] There is a major role of "super-spreading events", where many people are infected by one person.[5] These generally occur usually indoors, where groups of people remain in poor ventilation for longer periods.[5] It transmits via aerosols particularly in these crowded and less ventilated indoor spaces, which are particularly effective for transmitting the virus, such as restaurants, nightclubs, public transport and gatherings such as funerals.[8][9][4] Another important site for transmission is between members of the same household.[5]

It may be possible that people may be infected if they touch contaminated surfaces and then their eyes, nose or mouth with unwashed hands (fomite transmission), but this has not been conclusively demonstrated.[6][4][5] Surfaces are easily decontaminated with household disinfectants which destroy the virus outside the human body or on the hands.[10] Disinfectants or bleach are not a medical treatment for COVID-19, and cause health problems when not used properly, such as when used inside the human body.[11]

Sputum and saliva carry large amounts of virus.[5] Although COVID-19 is not a sexually transmitted infection, being physically close during sexual contact may transmit the virus.[5] The virus may occur in breast milk, but transmission this way has not been shown, and mother-to-child transmission rarely occurs.[5]

Routes

Respiratory route

A man coughing, with droplets dispersing widely into the surrounding air
The main route of transmission of COVID-19 is respiratory droplets expelled from the mouth and nose when a person sneezes, coughs, or speaks.

The COVID-19 virus spreads mainly through the air, via small droplets produced when an infected person breathes, coughs, sneezes, or talks. Many of these droplets are too heavy to hang in the air, and fall to the ground. However, some become airborne for longer periods, and can cause transmission even if a person has left the room, or outside the recommended social distance.[12][2][9] The closer a person interacts with someone who is infected, and the longer that interaction, the more likely the virus is to transmit.[1] The droplet form of transmission is thought to be the main way the virus spreads. These small droplets can land on the mouths or noses of other people and be inhaled into the lungs, to cause new infection.[1] Indoors, the virus can build up in the air via suspended fine particles such as those in aerosols, particularly where there is inadequate ventilation, and if the infected person performs a high risk activity such as exercising or singing.[1]

Controversy

Airborne transmission of COVID-19 has been shown to occur in specific instances, particularly indoors, via aerosols, smaller droplets that are able to stay suspended in the air for longer periods of time.[9] This is considered to be part of the respiratory route of transmitting the virus.[5] The airborne route, also known as droplet nuclei, was classically defined as smaller droplets that are less than 5 microns. However, the distinction between airborne and droplet transmission is not clear cut, and is likely a false dichotomy.[5]

As the pandemic progressed the WHO initially stated that the virus was not airborne. However, they updated their guidance in June 2020,[13] and the ECDC concurred that the virus can transmit this way. [4] This was because multiple outbreaks have been reported in indoor locations where infected persons spend long periods of time, such as restaurants, choir practices, religious venues and nightclubs.[14] The CDC concurred with the WHO and the ECDC that airborne transmission does in fact occur sometimes, in October 2020, after previously in error publishing a draft version recognizing airborne transmission on their website.[1][15] This led several experts to accuse the CDC of political interference.[16][17][18]

Medical

A tube and a camera being inserted into the mouth of a patient
Tracheal intubation is an example of an aerosol-generating procedure that carries increased risk of transmission from an infected patient.

Some medical procedures performed on COVID-19 patients in health facilities are aerosol-generating.[9][19] WHO recommends the use of filtering facepiece respirators such as N95 masks or FFP2 masks in settings where aerosol-generating procedures are performed, while CDC and the European Centre for Disease Prevention and Control recommend these controls in all situations involving the care of COVID-19 patients.[20]

Toilet

There has been concern that toilet aerosols generated by flushing contaminated toilets may spread the COVID-19 virus. WHO recommends that people suspected or confirmed with COVID-19 should use their own toilet, and while flushing the toilet lid should be down to block both droplets and aerosol clouds.[21]

Superspreading events

It often spreads in clusters, where infections can be traced back to an index case or geographical location.[22] There is a major role of "super-spreading events", where many people are infected by one person.[5] These generally occur usually indoors, where groups of people remain in poor ventilation for longer periods.[5]

Direct contact

Physical intimacy

A close-up photograph of two people kissing
Kissing carries high risk of COVID-19 transmission due to high levels of virus in the saliva.

The virus spreads through saliva and mucus, and kissing can easily transmit COVID-19. It is possible that direct contact with feces including anilingus may also lead to virus transmission.[23] However, as of July 2020 there have been no published reports of COVID-19 transmission through feces or urine.[20] While COVID‑19 is not a sexually transmitted infection, physical intimacy carries a high risk of transmission due to close proximity.[24]

Hand washing is a control against direct contact transmission.[12] Others include avoiding kissing and avoiding casual sex.[23][24] During physical intimacy, barriers such as face masks, condoms, or dental dams can be used, and socially distanced intimacy can be practiced through mutual masturbation or cybersex.[23]

Mother to child

As of July 2020, there were no cases of transmission from mother to baby during pregnancy.[20][25] Studies have found no viable virus in breast milk.[20] The WHO recommends that mothers with suspected or confirmed COVID-19 should be encouraged to initiate or continue to breastfeed.[26][20]

Indirect contact

Objects and surfaces

It may be possible that a person can get COVID-19 by touching a surface or object that has the virus on it (called a fomite), and then touching their own mouth, nose, or possibly their eyes - although this has not yet been been documented.[6][4] This is not thought to be the main way the virus spreads.[12][2][9] On surfaces the amount of viable active virus decreases over time until it can no longer cause infection. One study indicated that the virus can be detected for up to four hours on copper, up to one day on cardboard, and up to three days on plastic (polypropylene) and stainless steel (AISI 304).[2][27][28] There

Hand washing and periodic cleaning of surfaces are controls against indirect contact transmission through fomites.[9] Surfaces are easily decontaminated with household disinfectants which destroy the virus outside the human body. Note that disinfectants or bleach are not a treatment for COVID‑19, and cause health problems when not used properly, such as when used on or inside the human body.[29]

Food and water

There is currently no evidence to support transmission of COVID-19 associated with food.[30][31]

While virus RNA has been found in untreated wastewater, as of May 2020 there is little evidence of infectious virus in wastewater or drinking water.[21][32][33]

Animal vectors

There are a small number of cases of spread from people to pets, including cats and dogs. Other cases include lions and tigers at a New York zoo, and minks on farms in the Netherlands.[34][35] In a laboratory settings, animals shown to be infected include ferrets, cats, golden Syrian hamsters, rhesus macaques, cynomolgus macaques, grivets, common marmosets, and dogs.[34][36] By contrast, mice, pigs, chickens, and ducks do not seem to become infected or spread the infection.[34] There is no evidence that insect disease vectors such as mosquitoes or ticks spread COVID-19.[30]

CDC recommends that pet owners limit their pet's interaction with people outside their household. Face coverings are not recommended on pets because covering a pet's face could harm them, and they should not be disinfected with cleaning products not approved for animal use.[37] People sick with COVID-19 should avoid contact with pets and other animals.[36][37]

The risk of COVID-19 spreading from animals to people is considered to be low. Although the virus likely originated in bats, the pandemic is sustained through human-to-human spread.[34][36] Pets do not appear to play a role in spreading COVID-19, but there are reports from infected mink farms indicating transmission to humans is a possibility.[36]

Reproduction number

COVID-19 spreads easily between people—easier than influenza but not as easily as measles.[12]

Estimates of the number of people infected by one person with COVID-19, the R0, have varied. The WHO's initial estimates of R0 were 1.4–2.5 (average 1.95); however an early April 2020 review found the median R0 to be 5.7 and the basic R0 (without control measures) to be as high as 8.9.[38]

Source control may be used to partially inhibit spread.[citation needed]

Duration of transmissibility

People are most infectious when they show symptoms, even if mild or non-specific, but may be infectious for up to two days before symptoms appear. They remain infectious an estimated seven to twelve days in moderate cases and an average of two weeks in severe cases.[2][9] Research has indicated that viral load peaks around the day of symptom onset and declines after, as measured by RNA studies.[20]

The possibility of transmission for completely asymptomatic cases is unclear.[2][9] A recent systematic review estimated that the proportion of truly asymptomatic cases ranges from 6% to 41%, with some limitations ("asymptomatic" was not very well defined). A recent study from China with a clear definition of asymptomatic infections estimated a proportion of 23%.[20]

References

  1. ^ a b c d e f g h i j k l m "How COVID-19 Spreads". U.S. Centers for Disease Control and Prevention (CDC). 18 September 2020. Archived from the original on 19 September 2020. Retrieved 20 September 2020.
  2. ^ a b c d e f g "Q & A on COVID-19: Basic facts". European Centre for Disease Prevention and Control. Retrieved 18 September 2020. Cite error: The named reference "ECDCQA" was defined multiple times with different content (see the help page).
  3. ^ "Quarantine for coronavirus (COVID-19)". Australian Government Department of Health. Retrieved 25 September 2020.
  4. ^ a b c d e f g h i "Transmission of COVID-19". European Centre for Disease Prevention and Control. Retrieved 12 September 2020.
  5. ^ a b c d e f g h i j k l m Meyerowitz, Eric A.; Richterman, Aaron; Gandhi, Rajesh T.; Sax, Paul E. (17 September 2020). "Transmission of SARS-CoV-2: A Review of Viral, Host, and Environmental Factors". Annals of Internal Medicine. doi:10.7326/M20-5008. ISSN 0003-4819. PMID 32941052.
  6. ^ a b c "Transmission of SARS-CoV-2: implications for infection prevention precautions" (PDF). www.who.int. World Health Organization. 9 July 2020. Archived from the original on 9 July 2020. Retrieved 18 September 2020.
  7. ^ Liu, Tao; Gong, Dexin; Xiao, Jianpeng; Hu, Jianxiong; He, Guanhao; Rong, Zuhua; Ma, Wenjun. "Cluster infections play important roles in the rapid evolution of COVID-19 transmission: A systematic review". International Journal of Infectious Diseases. 99: 374–380. doi:10.1016/j.ijid.2020.07.073. ISSN 1201-9712. PMC 7405860. PMID 32768702.
  8. ^ Kohanski MA, Lo LJ, Waring MS (July 2020). "Review of indoor aerosol generation, transport, and control in the context of COVID-19". International Forum of Allergy & Rhinology. n/a (n/a). doi:10.1002/alr.22661. PMC 7405119. PMID 32652898.
  9. ^ a b c d e f g h "Q&A: How is COVID-19 transmitted?". World Health Organization. 9 July 2020. Retrieved 13 August 2020. Cite error: The named reference ":9" was defined multiple times with different content (see the help page).
  10. ^ "Q&A: How is COVID-19 transmitted?". World Health Organization. 9 July 2020. Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  11. ^ "Household cleaners and disinfectants can cause health problems when not used properly". U.S. Centers for Disease Control and Prevention (CDC). 24 April 2020. Retrieved 6 May 2020.
  12. ^ a b c d "How COVID-19 Spreads". U.S. Centers for Disease Control and Prevention. 16 June 2020. Retrieved 24 July 2020.{{cite web}}: CS1 maint: url-status (link)
  13. ^ Cite error: The named reference WHOTransmit was invoked but never defined (see the help page).
  14. ^ Leclerc, Quentin J.; Fuller, Naomi M.; Knight, Lisa E.; CMMID COVID-19 Working Group; Funk, Sebastian; Knight, Gwenan M. (5 June 2020). "What settings have been linked to SARS-CoV-2 transmission clusters?". Wellcome Open Research. 5: 83. doi:10.12688/wellcomeopenres.15889.2. ISSN 2398-502X.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  15. ^ News, A. B. C. "CDC abruptly removes new guidance on coronavirus airborne transmission". ABC News. Retrieved 6 October 2020. {{cite web}}: |last= has generic name (help)
  16. ^ Tanne, Janice Hopkins (24 September 2020). "Covid-19: CDC publishes then withdraws information on aerosol transmission". BMJ. 370. doi:10.1136/bmj.m3739. ISSN 1756-1833. PMID 32973037.
  17. ^ Avril, Tom. "As CDC reverses itself on COVID-19, Americans are losing trust, warn public-health veterans". https://www.inquirer.com. Retrieved 6 October 2020. {{cite web}}: External link in |website= (help)
  18. ^ "'Very Likely a Scandal': Demands for Answers as CDC Abruptly Deletes Guidance on Airborne Spread of Coronavirus". Common Dreams. Retrieved 6 October 2020.
  19. ^ Tran K, Cimon K, Severn M, Pessoa-Silva CL, Conly J (2012). "Aerosol generating procedures and risk of transmission of acute respiratory infections to healthcare workers: a systematic review". PLOS ONE. 7 (4): e35797. Bibcode:2012PLoSO...735797T. doi:10.1371/journal.pone.0035797. PMC 3338532. PMID 22563403.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  20. ^ a b c d e f g "Transmission of SARS-CoV-2: implications for infection prevention precautions" (PDF). www.who.int. World Health Organization. 9 July 2020. Archived from the original on 9 July 2020. Retrieved 18 September 2020.
  21. ^ a b "Water, sanitation, hygiene, and waste management for SARS-CoV-2, the virus that causes COVID-19". World Health Organization. 29 July 2020. Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  22. ^ Liu, Tao; Gong, Dexin; Xiao, Jianpeng; Hu, Jianxiong; He, Guanhao; Rong, Zuhua; Ma, Wenjun. "Cluster infections play important roles in the rapid evolution of COVID-19 transmission: A systematic review". International Journal of Infectious Diseases. 99: 374–380. doi:10.1016/j.ijid.2020.07.073. ISSN 1201-9712. PMC 7405860. PMID 32768702.
  23. ^ a b c "Sex and Coronavirus Disease 2019 (COVID-19)" (PDF). New York City Department of Health. 6 August 2020. Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  24. ^ a b "COVID-19 and Our Communities". ACON (New South Wales). 3 August 2020. At section "Sex and COVID-19". Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  25. ^ "Q & A on COVID-19: Medical information". European Centre for Disease Prevention and Control. 24 April 2020. Retrieved 21 August 2020.{{cite web}}: CS1 maint: url-status (link)
  26. ^ "Breastfeeding and COVID-19" (PDF). www.who.int. World Health Organization. 23 June 2020. Archived from the original on 23 June 2020. Retrieved 18 September 2020.
  27. ^ "New coronavirus stable for hours on surfaces". National Institutes of Health. 17 March 2020. Archived from the original on 23 March 2020. Retrieved 30 April 2020.
  28. ^ van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. (April 2020). "Aerosol and Surface Stability of SARS-CoV-2 as Compared with SARS-CoV-1". New England Journal of Medicine. 382 (16): 1564–1567. doi:10.1056/NEJMc2004973. PMC 7121658. PMID 32182409.
  29. ^ "COVID-19: Cleaning And Disinfecting Your Home". U.S. Centers for Disease Control and Prevention. 27 May 2020. Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  30. ^ a b "Coronavirus Disease 2019 (COVID-19): Frequently Asked Questions". U.S. Centers for Disease Control and Prevention. 15 July 2020. Retrieved 24 July 2020.{{cite web}}: CS1 maint: url-status (link)
  31. ^ "Q&A on COVID-19: Various". European Centre for Disease Prevention and Control. 24 April 2020. Retrieved 21 August 2020.{{cite web}}: CS1 maint: url-status (link)
  32. ^ Corpuz, Mary Vermi Aizza; Buonerba, Antonio; Vigliotta, Giovanni; Zarra, Tiziano; Ballesteros, Florencio; Campiglia, Pietro; Belgiorno, Vincenzo; Korshin, Gregory; Naddeo, Vincenzo (November 2020). "Viruses in wastewater: occurrence, abundance and detection methods". Science of the Total Environment. 745: 140910. Bibcode:2020ScTEn.745n0910C. doi:10.1016/j.scitotenv.2020.140910. PMC 7368910. PMID 32758747.
  33. ^ "Information for Sanitation and Wastewater Workers on COVID-19". U.S. Centers for Disease Control and Prevention. 28 May 2020. Retrieved 13 August 2020.{{cite web}}: CS1 maint: url-status (link)
  34. ^ a b c d "COVID-19 and Animals". U.S. Centers for Disease Control and Prevention. 22 June 2020. Retrieved 24 July 2020.{{cite web}}: CS1 maint: url-status (link)
  35. ^ "USDA Statement on the Confirmation of COVID-19 in a Tiger in New York". United States Department of Agriculture. 5 April 2020. Archived from the original on 15 April 2020. Retrieved 16 April 2020.
  36. ^ a b c d "Questions and Answers on COVID-19". World Organisation for Animal Health. 9 June 2020. Retrieved 23 July 2020.{{cite web}}: CS1 maint: url-status (link)
  37. ^ a b "COVID-19: If You Have Pets". U.S. Centers for Disease Control and Prevention. 28 June 2020. Retrieved 24 July 2020.{{cite web}}: CS1 maint: url-status (link)
  38. ^ Sanche, S.; Lin, Y. T.; Xu, C.; Romero-Severson, E.; Hengartner, E.; Ke, R. (July 2020). "High Contagiousness and Rapid Spread of Severe Acute Respiratory Syndrome Coronavirus 2". Emerging Infectious Diseases. 26 (7): 1470–1477. doi:10.3201/eid2607.200282. PMID 32255761. S2CID 215410037.


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