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Transmission of COVID-19

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Transmission of COVID-19
Other namesMode of spread of COVID-19
Covid-19 Aerosol.jpg
The respiratory route of spread of COVID-19, encompassing larger droplets and aerosols.
SpecialtyInfection prevention and control
TypesRespiratory route, respiratory droplet, airborne transmission, fomites
PreventionFace coverings, quarantine, physical/social distancing, ventilation, hand washing, vaccination
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The transmission of COVID-19 is the passing of coronavirus disease 2019 from person to person. The disease is mainly transmitted via the respiratory route when people inhale droplets and particles that infected people release as they breathe, talk, cough, sneeze, or sing.[1] Infected people are more likely to transmit COVID-19 the when they are physically close. However, infection can occur over longer distances, particularly indoors.[1]

Infectivity begins as early as three days before symptoms appear, and people are most infectious just prior to and during the onset of symptoms.[2] It declines after the first week, but infected people remain contagious for up to 20 days. People can spread the disease even if they are asymptomatic.[3][4][2]

Infectious particles range in size from aerosols that remain suspended in the air for long periods of time to larger droplets that remain airborne or fall to the ground.[1][5] Various groups utilise terms such as "airborne" and "droplet" both in technical and general ways, leading to confusion around terminology.[6] Additionally, COVID-19 research has redefined the traditional understanding of how respiratory viruses transmit.[5][7] The largest droplets of respiratory fluid do not travel far, and can be inhaled or land on mucous membranes on the eyes, nose, or mouth to infect.[1] Aerosols are highest in concentration when people are in close proximity, which leads to easier viral transmission when people are physically close,[1][5][7] but airborne transmission can occur at longer distances, mainly in locations that are poorly ventilated;[1] in those conditions small particles can remain suspended in the air for minutes to hours.[1]

The number of people generally infected by one infected person varies;[8] with only 10 to 20% of people responsible for the diseases spread.[9] It often spreads in clusters, where infections can be traced back to an index case or geographical location.[10] Often in these cases, superspreading events occur, where many people are infected by one person.[8]

A person can get COVID-19 indirectly by touching a contaminated surface or object before touching their own mouth, nose, or eyes,[2][11] though strong evidence suggests this does not contribute substantially to new infections.[1] Although it is considered possible, there is no direct evidence of the virus being transmitted by skin to skin contact.[8] The virus is not known to spread through feces, urine, breast milk, food, wastewater, drinking water, or animal disease vectors (though some animals can contract the virus from humans).[11][12] It very rarely transmits from mother to baby during pregnancy.[8]

Infectious period

After people are infected with COVID-19, they are able to transmit the disease to other people from one to three days before developing symptoms, known as presymptomatic transmission.[2] Contact tracing is used to find and contact people whom have been in contact with an infected individual in the 48 to 72 hours before they develop symptoms, or before their test date if asymptomatic.[2]

People are most infectious when they show symptoms—even if mild or non-specific—as the viral load is highest at this time.[2][11] They remain infectious, on average, seven to twelve days in moderate cases, and two weeks in severe cases.[13][14][11]

Asymptomatic transmission

People who are completely asymptomatic are able to transmit the virus.[1] A systematic review estimated that the proportion of asymptomatic cases ranges from 6 to 41%.[11] Although asymptomatic, they can have the same viral load as symptomatic and presymptomatic cases, and are able to transmit the virus.[2] However, the infectious period of asymptomatic cases has been observed to be shorter with faster viral clearance.[2]

Modes of transmission

An infected person breathes out the virus in small liquid droplets and particles. Multiple terms are used to describe particles of different sizes, and some are used specifically and technically by some groups, and generally by others. This introduces confusion in describing how COVID-19 transmits.[15] The risk of transmission is higher when a susceptible person is in close proximity to an infected person, but transmission can occur across a room.[16][17] Droplets and aerosols vary in size.[18] However, the risk of transmission from all size droplets and aerosols is always lower with good indoor ventilation or outdoors.[19]

Respiratory route (droplets and airborne particles)

The largest droplets produced during exhalation are generally more than 100 microns in diameter, and may fall to the ground within seconds due to gravity.[20][21] These droplets, referred to as "respiratory fluids" that are "splashed or sprayed" by the US CDC, can only transmit COVID-19 at short distances—a metre or a few metres.[1] Social distancing reduces the transmission risk from this route. The vast majority of particles exhaled are smaller, and remain airborne for longer periods.[22] Generally, humans produce droplets with sizes ranging from less than a micrometre to over 100 micrometres from exhalation.[22]

Video explainer on reducing airborne transmission of COVID-19 indoors

Droplets of various sizes can stay suspended in the air for at least minutes and move across a room.[13][23][24][25] As these droplets are suspended in air they form an aerosol, and transmission via these droplets is called aerosol or airborne transmission.[26][27]

There is substantial evidence for transmission events over longer distances that is associated with being indoors, particularly in less ventilated spaces. Airborne transmission usually occurs indoors in high risk locations,[28] including restaurants, hospitals,[29] choir practices,[16] fitness classes, nightclubs, offices, and religious venues.[30][27]

Examples

Repeatedly documented examples of airborne transmission have been shown, generally where infected persons spend long periods of time, such as restaurants and nightclubs.[13][31][32] They occur despite there not being the close proximity required for the previously theorised droplet transmission. Early examples included a choir practice in Washington, a restaurant in Guangzhou,[17] a tour bus in Hunan,[33] and a church in Sydney.[34] The restaurant was poorly ventilated[17] (less than one air change per hour, much less than is recommended), and there was no close contact between the infected person and those who were infected, the latter of whom remained a few metres away.[17]

A superspreading event in a Skagit County, Washington, choral practice resulted in 32 to 52 of the 61 attendees infected.[35][16] An existing model of airborne transmission (the Wells-Riley model) was adapted to help understand why crowded and poorly ventilation spaces promote transmission.[16] Airborne transmission also occurs in healthcare settings; long distance dispersal of virus particles has been detected in ventilation systems of a hospital.[29]

Controversy

Aerosol transmission of SARS-CoV-2 has been the subject of controversy. The WHO initially considered it to be insignificant, which led to widespread criticism from scientists. In July 2020, the WHO changed its guidance, saying that short-range aerosol transmission cannot be ruled out in these situations.[36] In October 2020, it recognised that while evidence suggested the main mode of transmission was by respiratory droplets, airborne transmission is occurring, particularly in high risk indoor settings, where there is crowding and less ventilation. The advice was further changed in April 2021 to plainly state: "A person can be infected when aerosols or droplets containing the virus are inhaled." It advises avoiding the "Three C's": crowded places, close contact settings, and confined and enclosed spaces.[30]

The US CDC has been criticised for delays in informing the public about airborne transmission, with John Allan from Harvard University's School of Public Health writing "many scientists have known that airborne transmission of the virus was happening since February. The CDC somehow failed to recognize the accumulating evidence that airborne transmission is important and therefore failed to alert the public."[37][38] Since then the CDC has updated its guidance to reflect the importance of airborne/aerosol transmission.[39]

In Canada, the controversy has been attributed to complexities involving the N-95 respirator supply chain and fears that it may run out.[40] The Public Health Agency of Canada recognised airborne transmission in November 2020, stating the relative importance between airborne transmission and large droplet transmission is unknown.[41]

In Australia, the controversy involved PPE guidelines, with varying expert bodies disagreeing on how to best protect healthcare workers.[42][43][44] In 2021, a new guideline was created by a new body, which endorsed the use of N-95 respirators in most circumstances.[45]

Other aerosolization modes

An infected person breathes out the virus when they breathe, speak, sing, and cough. The virus-containing droplets are produced in the lungs, throat and mouth due to the motion of breathing.[25] However, virus-containing droplets may be able to be produced in other ways, in particular circumstances, including medical procedures and behaviours by infected people.

Aerosol-generating medical procedures
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 can be designated as aerosol-generating procedures[13][46] (AGP). The WHO recommends the use of filtering facepiece respirators such as N95 or FFP2 masks in settings where aerosol-generating procedures are performed,[11] while the U.S. CDC and the European Centre for Disease Prevention and Control recommend these controls in all situations related to COVID-19 patient treatment (other than during crisis shortages).[47][48][49]

However, some medical procedures have been designated as AGPs without actually measuring the aerosols they produce.[50] The aerosols generated by some AGPs have been measured and found to be less than the aerosols produced by breathing[51][52] For example, Continuous positive airway pressure (CPAP)has been designated an AGP but patients provided with CPAP generated less aerosols than those breathing normally,[52] which has led to calls to reconsider AGPs.[50]

Aerosol-generating behaviours

In healthcare settings, guidelines have noted that behaviours such as coughing contribute to aerosol transmission, with appropriate airborne precautions needed.[53]

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.[12]

Other modes of transmission

Objects and surfaces

A silver-colored door handle on a white door
Surfaces that are often touched such as door handles may transmit COVID-19, although is not thought to be the main way the virus spreads.

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 eyes,[54] but it is not thought to be the main mode of transmission.[13][55][8][11][14][56] Viable virus or RNA has been detected on contaminated surfaces for periods ranging from hours to days, depending on environmental conditions. As of July 2020, there have not been specific reports that directly demonstrated transmission via fomites, although fomite transmission is hard to distinguish from transmission from the infectious person themselves.[11]

The amount of viable active virus on surfaces decreases over time until it can no longer cause infection. One study indicated that the virus can be, at a maximum, detected for four hours on copper, one day on cardboard, and three days on plastic (polypropylene) and stainless steel (AISI 304).[14][57][58] In October 2020, medical researchers concluded SARS-CoV-2 can remain on common surfaces for up to 28 days.[59] It has been shown that indirect transmission occurs mostly indoors, as sunlight inactivates the virus.[60]

Since the virus is stable on human skin,[60] hand washing and periodic surface cleaning impede indirect contact transmission through fomites.[13] Surfaces are easily decontaminated with household disinfectants that destroy the virus outside the human body. 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.[13][61][62]

The rate of fomite transmission decreases steadily with time,[60] which is why it can be useful to let incoming packages sit untouched for a few days before opening them to reduce the risk of contracting the disease.

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 saliva.

The virus can spread 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,[63] but as of July 2020 there have been no published reports of COVID-19 transmission through feces or urine.[11] While COVID‑19 is not a sexually transmitted infection, physical intimacy carries a high risk of transmission due to close proximity.[64]

Hand washing impedes direct contact transmission.[56] Other behaviours include the avoidance of kissing and casual sex.[63][64] 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.[63]

Mother to child

As of July 2020, there have been no cases of transmission from mother to baby during pregnancy.[11][65] Studies have not found any viable virus in breast milk.[11] The WHO recommends that mothers with suspected or confirmed COVID-19 should be encouraged to initiate or continue to breastfeed.[11][66]

Food and water

The risk of food-related transmission is low.[67] Less than 1 in 10,000 contacts with contaminated surfaces, including non-food-related surfaces, lead to infection.[68]

While viral RNA has been found in untreated wastewater, as of May 2020 there has been little evidence of infectious virus in wastewater or drinking water.[12][69][70]

After the COVID-19 outbreak in Beijing in June, evidence of food transmission was reported in China in early July 2020 by the discovery of SARS-CoV-2 on frozen foods, packaging materials, and storage environments.[71][better source needed][72] On October 17, the Chinese CDC reported that they separated out live SARS-CoV-2 from packaging cold chain imported food during an investigation of another outbreak in Qingdao in October.[73] As of October 2020, there has been no direct evidence of general public contracting the virus from contaminated food packaging.[74]

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 (see also Cluster 5 article).[75][76] In laboratory settings, animals shown to be infected include ferrets, cats, golden Syrian hamsters, rhesus macaques, cynomolgus macaques, grivets, common marmosets, and dogs.[75][77][78] By contrast, mice, pigs, chickens, and ducks do not seem to become infected or spread the infection.[75] There is no evidence that insect disease vectors such as mosquitoes or ticks spread COVID-19.[79]

The U.S. CDC recommended that pet owners limit their pet's interactions with people outside their household. Face coverings are not recommended on pets, as covering their faces could harm them, and they should not be disinfected with cleaning products not approved for animal use.[80] People sick with COVID-19 should avoid contact with pets and other animals.[77][80]

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.[75][77] Pets do not appear to play a role in spreading COVID-19, but there are reports from infected mink farms that indicate transmission to humans is a possibility.[77]

Clusters and other patterns

Many people do not transmit the virus, but some transmit to many people, and the virus is considered to be "overdispersed" - the transmission rate has high heterogeneity.[8][81] "Super-spreading events" occur from this minority of infected people, usually in high risk venues including restaurants, nightclubs, places of worship, and they generally occur indoors.[8] It often spreads in these clusters, where infections can be traced back to an index case or geographical location.[10] These generally occur usually indoors, where groups of people remain in poor ventilation for longer periods.[8] It transmits via aerosols particularly in these crowded and confined indoor spaces, which are particularly effective for transmitting the virus, such as restaurants, nightclubs or choirs.[55][30][82] Another important site for transmission is between members of the same household.[8]

As of September 2020 it was estimated that, on average, one infected person can infect two or three other people.[14] This is more infectious than influenza, but less so than measles.[56]

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.[83] In November, a systematic review estimated R0 to be approximately 2.87 (95% CI, 2.39–3.44).[84]

Effect of vaccination

People that have been vaccinated can still spread COVID-19, though at reduced rates when compared to someone who has not.[85]

References

  1. ^ a b c d e f g h i j CDC (11 February 2020). "Scientific Brief: SARS-CoV-2 Transmission". Centers for Disease Control and Prevention. Retrieved 10 May 2021.
     • "COVID-19: epidemiology, virology and clinical features". GOV.UK. Retrieved 18 October 2020.
     • Communicable Diseases Network Australia. "Coronavirus Disease 2019 (COVID-19) - CDNA Guidelines for Public Health Units". Version 4.4. Australian Government Department of Health. Retrieved 17 May 2021.
     • Public Health Agency of Canada (3 November 2020). "COVID-19: Main modes of transmission". aem. Retrieved 18 May 2021.
     • "Transmission of COVID-19". European Centre for Disease Prevention and Control. Retrieved 18 May 2021.
     • Meyerowitz EA, Richterman A, Gandhi RT, Sax PE (January 2021). "Transmission of SARS-CoV-2: A Review of Viral, Host, and Environmental Factors". Annals of Internal Medicine. 174 (1): 69–79. doi:10.7326/M20-5008. PMC 7505025. PMID 32941052.
     • "Coronavirus disease (COVID-19): How is it transmitted?". www.who.int. World Health Organization. 30 April 2021. Retrieved 9 May 2021.
  2. ^ a b c d e f g h Communicable Diseases Network Australia. "Coronavirus Disease 2019 (COVID-19) - CDNA Guidelines for Public Health Units". Version 4.4. Australian Government Department of Health. Retrieved 17 May 2021.
  3. ^ CDC (11 February 2020). "Coronavirus Disease 2019 (COVID-19)". Centers for Disease Control and Prevention. Retrieved 6 December 2020.
  4. ^ Clinical Questions about COVID-19: Questions and Answers Centers for Disease Control and Prevention
  5. ^ a b c Tang JW, Marr LC, Li Y, Dancer SJ (April 2021). "Covid-19 has redefined airborne transmission". BMJ. 373: n913. doi:10.1136/bmj.n913. PMID 33853842.
  6. ^ "Australian guidelines for SARS-CoV-2 infection prevention and control of COVID-19 in healthcare workers". app.magicapp.org. Retrieved 16 June 2021.
  7. ^ a b Morawska L, Allen J, Bahnfleth W, Bluyssen PM, Boerstra A, Buonanno G, et al. (May 2021). "A paradigm shift to combat indoor respiratory infection" (PDF). Science. 372 (6543): 689–691. Bibcode:2021Sci...372..689M. doi:10.1126/science.abg2025. PMID 33986171. S2CID 234487289.
  8. ^ a b c d e f g h i Meyerowitz EA, Richterman A, Gandhi RT, Sax PE (January 2021). "Transmission of SARS-CoV-2: A Review of Viral, Host, and Environmental Factors". Annals of Internal Medicine. 174 (1): 69–79. doi:10.7326/M20-5008. PMC 7505025. PMID 32941052.
  9. ^ Lessler J, Grantz K. "Overdispersion of COVID-19". Johns Hopkins Bloomberg School of Public Health. Retrieved 11 May 2021.
  10. ^ a b Liu T, Gong D, Xiao J, Hu J, He G, Rong Z, Ma W (October 2020). "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. PMC 7405860. PMID 32768702.
  11. ^ a b c d e f g h i j k l "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.
  12. ^ a b c "Water, sanitation, hygiene, and waste management for SARS-CoV-2, the virus that causes COVID-19" (PDF). www.who.int. 29 July 2020. Retrieved 14 October 2020.
  13. ^ a b c d e f g "Q&A: How is COVID-19 transmitted? (How is the virus that causes COVID-19 most commonly transmitted between people?)". www.who.int. 9 July 2020. Retrieved 14 October 2020.
  14. ^ a b c d "Q & A on COVID-19: Basic facts". www.ecdc.europa.eu. 25 September 2020. Retrieved 8 October 2020.
  15. ^ "MAGICapp - Making GRADE the Irresistible Choice - Guidelines and Evidence summaries". app.magicapp.org. Retrieved 16 June 2021.
  16. ^ a b c d Miller SL, Nazaroff WW, Jimenez JL, Boerstra A, Buonanno G, Dancer SJ, et al. (March 2021). "Transmission of SARS-CoV-2 by inhalation of respiratory aerosol in the Skagit Valley Chorale superspreading event". Indoor Air. 31 (2): 314–323. doi:10.1111/ina.12751. PMC 7537089. PMID 32979298.
  17. ^ a b c d Li Y, Qian H, Hang J, Chen X, Cheng P, Ling H, et al. (June 2021). "Probable airborne transmission of SARS-CoV-2 in a poorly ventilated restaurant". Building and Environment. 196: 107788. doi:10.1016/j.buildenv.2021.107788. PMC 7954773. PMID 33746341.
  18. ^ Jayaweera, Mahesh; Perera, Hasini; Gunawardana, Buddhika; Manatunge, Jagath (2020). "Transmission of COVID-19 virus by droplets and aerosols: A critical review on the unresolved dichotomy". Environmental Research. 188: 4. Bibcode:2020ER....188j9819J. doi:10.1016/j.envres.2020.109819. ISSN 0013-9351. PMC 7293495. PMID 32569870.
  19. ^ The Lancet Respiratory Medicine (December 2020). "COVID-19 transmission-up in the air". The Lancet. Respiratory Medicine. 8 (12): 1159. doi:10.1016/s2213-2600(20)30514-2. PMC 7598535. PMID 33129420.
  20. ^ Balachandar S, Zaleski S, Soldati A, Ahmadi G, Bourouiba L (2020). "Host-to-host airborne transmission as a multiphase flow problem for science-based social distance guidelines". International Journal of Multiphase Flow. 132: 103439. arXiv:2008.06113. doi:10.1016/j.ijmultiphaseflow.2020.103439. PMC 7471834.
  21. ^ Netz RR (August 2020). "Mechanisms of Airborne Infection via Evaporating and Sedimenting Droplets Produced by Speaking". The Journal of Physical Chemistry B. 124 (33): 7093–7101. doi:10.1021/acs.jpcb.0c05229. PMC 7409921. PMID 32668904.
  22. ^ a b Johnson GR, Morawska L, Ristovski ZD, Hargreaves M, Mengersen K, Chao CY, et al. (2011). "Modality of human expired aerosol size distributions". Journal of Aerosol Science. 42 (12): 839–851. Bibcode:2011JAerS..42..839J. doi:10.1016/j.jaerosci.2011.07.009.
  23. ^ de Oliveira PM, Mesquita LC, Gkantonas S, Giusti A, Mastorakos E (January 2021). "Evolution of spray and aerosol from respiratory releases: theoretical estimates for insight on viral transmission". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences. 477 (2245): 20200584. Bibcode:2021RSPSA.47700584D. doi:10.1098/rspa.2020.0584. PMC 7897643. PMID 33633490.
  24. ^ Lednicky JA, Lauzardo M, Fan ZH, Jutla A, Tilly TB, Gangwar M, et al. (November 2020). "Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients". International Journal of Infectious Diseases. 100: 476–482. doi:10.1016/j.ijid.2020.09.025. PMC 7493737. PMID 32949774.
  25. ^ a b Bourouiba L (5 January 2021). "The Fluid Dynamics of Disease Transmission". Annual Review of Fluid Mechanics. 53 (1): 473–508. Bibcode:2021AnRFM..5360220B. doi:10.1146/annurev-fluid-060220-113712. ISSN 0066-4189. S2CID 225114407.
  26. ^ Samet JM, Prather K, Benjamin G, Lakdawala S, Lowe JM, Reingold A, et al. (January 2021). "Airborne Transmission of SARS-CoV-2: What We Know". Clinical Infectious Diseases: ciab039. doi:10.1093/cid/ciab039. PMC 7929061. PMID 33458756.
  27. ^ a b Epperly DE, Rinehart KR, Caney DN (2020). "COVID-19 Aerosolized Viral Loads, Environment, Ventilation, Masks, Exposure Time, Severity, And Immune Response: A Pragmatic Guide Of Estimates". medRxIv. doi:10.1101/2020.10.03.20206110.
  28. ^ "'Danger lurks inside': German aerosol experts say Covid restrictions should target indoor areas". www.thelocal.de. 12 April 2021. Retrieved 25 April 2021.
  29. ^ a b Nissen K, Krambrich J, Akaberi D, Hoffman T, Ling J, Lundkvist Å, et al. (November 2020). "Long-distance airborne dispersal of SARS-CoV-2 in COVID-19 wards". Scientific Reports. 10 (1): 19589. Bibcode:2020NatSR..1019589N. doi:10.1038/s41598-020-76442-2. PMC 7659316. PMID 33177563.
  30. ^ a b c "Q&A: How is COVID-19 transmitted? (What do we know about aerosol transmission?)". www.who.int. 9 July 2020. Retrieved 14 October 2020.
  31. ^ Leclerc QJ, Fuller NM, Knight LE, Funk S, Knight GM (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. PMC 7327724. PMID 32656368.
  32. ^ "COVID-19: epidemiology, virology and clinical features". GOV.UK. Retrieved 18 October 2020.
  33. ^ "Scientific Brief: SARS-CoV-2 and Potential Airborne Transmission". CDC. 5 October 2020. Retrieved 23 November 2020.
  34. ^ Katelaris, Anthea L.; Wells, Jessica; Clark, Penelope; Norton, Sophie; Rockett, Rebecca; Arnott, Alicia; Sintchenko, Vitali; Corbett, Stephen; Bag, Shopna K. (2021). "Epidemiologic Evidence for Airborne Transmission of SARS-CoV-2 during Church Singing, Australia, 2020". Emerging Infectious Diseases. 27 (6): 1677–1680. doi:10.3201/eid2706.210465. ISSN 1080-6040. PMC 8153858. PMID 33818372.
  35. ^ Hamner L, Dubbel P, Capron I, Ross A, Jordan A, Lee J, et al. (May 2020). "High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice - Skagit County, Washington, March 2020". MMWR. Morbidity and Mortality Weekly Report. 69 (19): 606–610. doi:10.15585/mmwr.mm6919e6. PMID 32407303.
  36. ^ Lewis D (July 2020). "Mounting evidence suggests coronavirus is airborne - but health advice has not caught up". Nature. 583 (7817): 510–513. Bibcode:2020Natur.583..510L. doi:10.1038/d41586-020-02058-1. PMID 32647382. S2CID 220470431.
  37. ^ Zhang R, Li Y, Zhang AL, Wang Y, Molina MJ (June 2020). "Identifying airborne transmission as the dominant route for the spread of COVID-19". Proceedings of the National Academy of Sciences of the United States of America. 117 (26): 14857–14863. doi:10.1073/pnas.2009637117. PMC 7334447. PMID 32527856.
  38. ^ Tanne JH (September 2020). "Covid-19: CDC publishes then withdraws information on aerosol transmission". BMJ. 370: m3739. doi:10.1136/bmj.m3739. PMID 32973037. S2CID 221881893.
  39. ^ CDC (11 February 2020). "Coronavirus Disease 2019 (COVID-19)". Centers for Disease Control and Prevention. Retrieved 8 May 2021.
  40. ^ "Canada's top doctor has been hesitant to say tiny airborne particles are spreading COVID-19. Under pressure, she reconsiders". FR24 News English. Retrieved 25 October 2020.
  41. ^ "COVID-19: Main modes of transmission". Public Health Agency of Canada. 3 November 2020. Retrieved 25 November 2020.
  42. ^ "Poor habits, apathetic medicos to blame". www.theaustralian.com.au. Retrieved 20 November 2020.
  43. ^ Khorshid O (20 November 2020). "Letter to Professor Gilbert" (PDF). Australian Medical Association.
  44. ^ Readfearn G (20 November 2020). "Australian Medical Association accuses Covid infection control group chair of 'tone deaf' comments". The Guardian. ISSN 0261-3077. Retrieved 20 November 2020.
  45. ^ "Home". National COVID-19 Clinical Evidence Taskforce. Retrieved 21 June 2021.
  46. ^ 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.
  47. ^ "Infection prevention and control and preparedness for COVID-19 in healthcare settings - fifth update" (PDF).
  48. ^ "Respiratory Protection During Outbreaks: Respirators versus Surgical Masks | | Blogs | CDC". Retrieved 25 November 2020.
  49. ^ CDC (11 February 2020). "Coronavirus Disease 2019 (COVID-19)". Centers for Disease Control and Prevention. Retrieved 29 November 2020.
  50. ^ a b Hamilton F, Arnold D, Bzdek BR, Dodd J, Reid J, Maskell N (May 2021). "Aerosol generating procedures: are they of relevance for transmission of SARS-CoV-2?". The Lancet. Respiratory Medicine: S2213260021002162. doi:10.1016/S2213-2600(21)00216-2. PMC 8102043. PMID 33965002.
  51. ^ Wilson NM, Marks GB, Eckhardt A, Clarke AM, Young FP, Garden FL, et al. (March 2021). "The effect of respiratory activity, non-invasive respiratory support and facemasks on aerosol generation and its relevance to COVID-19". Anaesthesia: anae.15475. doi:10.1111/anae.15475. PMID 33784793.
  52. ^ a b Hamilton FW, Gregson F, Arnold DT, Sheikh S, Ward K, Brown J, et al. (1 February 2021). "Aerosol emission from the respiratory tract: an analysis of relative risks from oxygen delivery systems". MedRxiv: 2021.01.29.21250552. doi:10.1101/2021.01.29.21250552. S2CID 231729315.
  53. ^ Communicable Diseases Network Australia; Australian Government Department of Health, Coronavirus Disease 2019 (COVID-19), Australian Government Department of Health, retrieved 22 May 2021
  54. ^ CDC (28 October 2020). "COVID-19 and Your Health". Centers for Disease Control and Prevention. Retrieved 8 February 2021.
  55. ^ a b "Transmission of COVID-19". www.ecdc.europa.eu. 7 September 2020. Retrieved 14 October 2020.
  56. ^ a b c "How COVID-19 Spreads". www.cdc.gov. 5 October 2020. Retrieved 7 October 2020.
  57. ^ "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.
  58. ^ 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". The New England Journal of Medicine. 382 (16): 1564–1567. doi:10.1056/NEJMc2004973. PMC 7121658. PMID 32182409.
  59. ^ Riddell S, Goldie S, Hill A, Eagles D, Drew TW (October 2020). "The effect of temperature on persistence of SARS-CoV-2 on common surfaces". Virology Journal. 17 (1): 145. doi:10.1186/s12985-020-01418-7. PMC 7538848. PMID 33028356. S2CID 222178243.
  60. ^ a b c Bueckert M, Gupta R, Gupta A, Garg M, Mazumder A (November 2020). "Infectivity of SARS-CoV-2 and Other Coronaviruses on Dry Surfaces: Potential for Indirect Transmission". Materials. 13 (22): 5211. Bibcode:2020Mate...13.5211B. doi:10.3390/ma13225211. PMC 7698891. PMID 33218120.
  61. ^ "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.
  62. ^ "COVID-19: Cleaning And Disinfecting Your Home". www.cdc.gov. 27 May 2020. Retrieved 7 October 2020.
  63. ^ a b c "Sex and Coronavirus Disease 2019 (COVID-19)" (PDF). New York City Department of Health. 6 August 2020. Retrieved 13 August 2020.
  64. ^ a b "COVID-19 and Our Communities". ACON (New South Wales). 3 August 2020. At section "Sex and COVID-19". Retrieved 13 August 2020.
  65. ^ "Q & A on COVID-19: Medical information". European Centre for Disease Prevention and Control. 24 April 2020. Retrieved 21 August 2020.
  66. ^ "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.
  67. ^ "Q&A on COVID-19: Various". European Centre for Disease Prevention and Control. 24 April 2020. Retrieved 21 August 2020.
  68. ^ "Science Brief: SARS-CoV-2 and Surface (Fomite) Transmission for Indoor Community Environments". Centers for Disease Control and Prevention. 11 February 2020. Retrieved 12 April 2021.
  69. ^ Corpuz MV, Buonerba A, Vigliotta G, Zarra T, Ballesteros F, Campiglia P, et al. (November 2020). "Viruses in wastewater: occurrence, abundance and detection methods". The Science of the Total Environment. 745: 140910. Bibcode:2020ScTEn.745n0910C. doi:10.1016/j.scitotenv.2020.140910. PMC 7368910. PMID 32758747.
  70. ^ "Information for Sanitation and Wastewater Workers on COVID-19". U.S. Centers for Disease Control and Prevention. 28 May 2020. Retrieved 13 August 2020.
  71. ^ Han J, Zhang X, He S, Jia P (October 2020). "Can the coronavirus disease be transmitted from food? A review of evidence, risks, policies and knowledge gaps". Environmental Chemistry Letters. 19: 5–16. doi:10.1007/s10311-020-01101-x. PMC 7529092. PMID 33024427.
  72. ^ Lam N (14 November 2020). "China has zeroed in on frozen food imports as it tries to keep a lid on Covid-19". South China Morning Post.
  73. ^ "中国疾病预防控制中心在冷链食品外包装分离到新冠活病毒" (in Chinese). 17 October 2020.
  74. ^ "Food chain role considered in WHO's COVID-19 origin report". Food Safety News. 1 April 2021.
  75. ^ a b c d "COVID-19 and Animals". www.cdc.gov. 22 June 2020. Retrieved 7 October 2020.
  76. ^ "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.
  77. ^ a b c d "Questions and Answers on COVID-19". World Organisation for Animal Health. 9 June 2020. Retrieved 23 July 2020.
  78. ^ Bosco-Lauth AM, Hartwig AE, Porter SM, Gordy PW, Nehring M, Byas AD, et al. (October 2020). "Experimental infection of domestic dogs and cats with SARS-CoV-2: Pathogenesis, transmission, and response to reexposure in cats". Proceedings of the National Academy of Sciences of the United States of America. 117 (42): 26382–26388. doi:10.1073/pnas.2013102117. PMC 7585007. PMID 32994343. S2CID 222170541.
  79. ^ "Coronavirus Disease 2019 (COVID-19): Frequently Asked Questions". www.cdc.gov. 15 July 2020. Retrieved 24 July 2020.
  80. ^ a b "COVID-19: If You Have Pets". www.cdc.gov. 28 June 2020. Retrieved 24 July 2020.
  81. ^ Endo A, Abbott S, Kucharski AJ, Funk S (2020). "Estimating the overdispersion in COVID-19 transmission using outbreak sizes outside China". Wellcome Open Research. 5: 67. doi:10.12688/wellcomeopenres.15842.3. PMC 7338915. PMID 32685698.
  82. ^ Kohanski MA, Lo LJ, Waring MS (October 2020). "Review of indoor aerosol generation, transport, and control in the context of COVID-19". International Forum of Allergy & Rhinology. 10 (10): 1173–1179. doi:10.1002/alr.22661. PMC 7405119. PMID 32652898.
  83. ^ Sanche S, Lin YT, Xu C, Romero-Severson E, Hengartner N, 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. PMC 7323562. PMID 32255761. S2CID 215410037.
  84. ^ Billah MA, Miah MM, Khan MN (11 November 2020). "Reproductive number of coronavirus: A systematic review and meta-analysis based on global level evidence". PLOS ONE. 15 (11): e0242128. Bibcode:2020PLoSO..1542128B. doi:10.1371/journal.pone.0242128. PMC 7657547. PMID 33175914.
  85. ^ Centers for Disease Control and Prevention, CDC. "Interim Estimates of Vaccine Effectiveness of BNT162b2 and mRNA-1273 COVID-19 Vaccines in Preventing SARS-CoV-2 Infection Among Health Care Personnel, First Responders, and Other Essential and Frontline Workers" (PDF). enters for Disease Control and Prevention (CDC).

External links

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