Transmission routes

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This page collects observations, interpretations, and consequences for action about Transmission Routes of SARS-CoV2. Please observe the structure of the page, when you add your content. Please use references where possible. Remember to find the relevant page. For example, if your observation is about Sources, please use that page, instead of posting your content here.

What is already known

  • Person to Person Transmission (close contact). [1]
    • Droplet infection
    • Cross-contamination of hands
  • Fomites. [1]
  • No evidence of vertical (mother-child) transmission. [1]
  • Potential of SARS-CoV2 to survive in aerosol. [2]

Feacal-oral transmission?

Observations

  • Some authors report that diarrhea is a common symptom of COVID19. [1]
  • Others report that diarrhea is not common everywhere (5% in China, 17% in Singapore), and may be a coincidental symptom. [3]
  • Based on data from 39 countries, SARS-CoV-2 can remain stable within water for up to 25 Days. Country-specific risk of infection posed by faecal contaminated water is environment-dependent, with water flow and temperature as important variables.[4]

Analysis and interpretation

  • The question raises, whether we should anticipate transmission routes as observed with SARS (via sewage overflow and aerosols)
  • Differences in reported frequency in diarrhea may be confounded by difficulty in the assessment. The definition of the symptom may not be standardized between studies. Often, it is also patient-reported, and reporting this symptom may be culturally biassed.

Consequences for action

  • Study fecal-oral transmission routes as risk factors for COVID19

Practical Risk of Aerosols

Observations

  • SARS-CoV2 stability in aerosol was experimentally tested, where authors measure the viability of virus on surfaces, after aerosol nebulizing [2]

Analysis and interpretation

  • Does 'viability on surface' mean that the virus is still (biologically) infectious? I would be hesitant to extrapolate the findings of Doremalen to that conclusion.

Consequences for action

  • Further study infectiousness of aerosols, for example in ferret models?

Choir singing and Corona risk

Observations

  • Several choir-based outbreaks of COVID19 have been observed. The specific risks of singing together, even when respecting 6 feet distance, have not been investigated. [5] [6] [7] [8]
    • A video with observations from Korea provides some insights (the video starts at 11:30, but you can watch all of it if you want to):
  • Other outbreaks, such as the one at the South Korean Call Centre, suggest that aerosol (airborne) transmission could play a part, in addition to droplet and indirect transmission. [9]
  • What we know: Speech and other vocal activities such as singing have been shown to generate air particles, with the rate of emission corresponding to voice loudness. [10]. Singing is comparable to continuous coughing, as demonstrated by spread of tuberculosis. [11]
  • A study of choir practice attendees suggests that transmission of COVID-19 was facilitated by close proximity and physical contact and may have been augmented by the act of singing. [12]

Analysis and interpretation

  • Observations could prompt public health authorities to add 'singing' to the list of risk-behaviors for COVID19 transmission. Biologically, it is plausible that singing increases the risk of transmission of respiratory diseases.

Consequences for action

  • In prevention programmes for COVID19, specific attention should go out to advising choirs and other singing groups.

References

  1. 1.0 1.1 1.2 1.3 Rothan, Hussin A., and Siddappa N. Byrareddy. "The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak." Journal of Autoimmunity (2020): 102433.
  2. 2.0 2.1 van Doremalen, Neeltje, et al. "Aerosol and surface stability of HCoV-19 (SARS-CoV-2) compared to SARS-CoV-1." medRxiv (2020).
  3. Ong, John, Barnaby Edward Young, and Sharon Ong. "COVID-19 in gastroenterology: a clinical perspective." Gut (2020).
  4. Shutler J, Zaraska K, Holding TM, Machnik M, Uppuluri K, Ashton I, et al. Risk of SARS-CoV-2 infection from contaminated water systems. medRxiv. 2020
  5. A choir decided to go ahead with rehearsal. Now dozens of members have COVID-19 and two are dead. Los Angeles Times. By RICHARD READ; SEATTLE BUREAU CHIEF: MARCH 29, 2020.
  6. Wei, W. E., Li, Z., Chiew, C. J., Yong, S. E., Toh, M. P., & Lee, V. J. (2020). Presymptomatic Transmission of SARS-CoV-2—Singapore, January 23–March 16, 2020. Morbidity and Mortality Weekly Report, 69(14), 411.
  7. Mangara, B. T., Napolitano, E. C., Passannante, M. R., McDonald, R. J., & Reichman, L. B. (1998). Mycobacterium tuberculosis miniepidemic in a church gospel choir. Chest, 113(1), 234-237.
  8. 45 of 60 People Who Went to Washington Choir Practice Have Coronavirus. The Daily Beast. Tracy Connor Executive Editor Published Mar. 30, 2020
  9. Suggested citation for this article: Park SY, Kim YM, Yi S, Lee S, Na BJ, Kim CB, et al. Coronavirus disease outbreak in call center, South Korea. Emerg Infect Dis. 2020 Aug [early release, cited on 2 May 2020]. https://doi.org/10.3201/eid2608.201274
  10. Asadi S, Wexler AS, Cappa CD, Barreda S, Bouvier NM, Ristenpart WD. Aerosol emission and super emissions during human speech increase with voice loudness. Sci Rep 2019;9:2348. 10.1038/s41598-019-38808-z
  11. Loudon RG, Roberts RM. Singing and the dissemination of tuberculosis. Am Rev Respir Dis 1968; 98: 297–300.
  12. Hamner L, Dubbel P, Capron I, et al. High SARS-CoV-2 Attack Rate Following Exposure at a Choir Practice - Skagit County, Washington, March 2020. MMWR Morb Mortal Wkly Rep. 2020;69(19):606-610. Published 2020 May 15. 2020