Beyond masks and hand hygiene, what factors impact transmission of Covid-19 in indoor gatherings?

Aside from factors specific to the source individual (eg, viral load in exhaled air, “superspreader” features, etc…) and host characteristics (eg, older age, obesity, immunocompromised state), transmission of SARS-CoV-2 in indoor settings may be impacted by several factors, including social distancing, ventilation of rooms/ direction of airflow, room occupancy, exposure time and higher risk activities, such as eating, talking loud, heavy breathing during exercise, laughing, coughing and sneezing. 1-4

  1. Physical distance from infected individuals. Although a “safe” distance of 6 feet has often been cited, increasing evidence suggests that SARS-CoV-2 may be spread not only by larger droplets but also by airborne route (ie, beyond 6 feet or shortly after an infected person leaves the area). In fact, 8 of 10 studies on horizontal droplet distance have reported droplets traveling more than 6 feet (2 meters), some cases up to 26 feet (8 meters), and 1 study documented virus at 13 feet (4 meters). Transmission beyond 6 feet is not surprising since even as early as 1948 beta streptococci were found 9.5 feet from 10% of people who were infected!1
  2. Quality of ventilation and direction of airflow in the room. Poorly ventilated rooms would be expected to have more potentially infectious droplets in the air for longer periods of time, even after an infected person leaves the area.
  3. Room occupancy. The higher the occupancy the more likely to have exhaled contaminated air from 1 or more infected persons (symptomatic or asymptomatic) with exposure of susceptible hosts.
  4. Exposure time. Exposure to contaminated air in the room even for a relatively short period of time (ie, >5-15 minutes) is likely to increase the risk of transmission.
  5. Activity of infected individual. Many activities such as singing, speaking loudly, eating, laughing, breathing heavily during exercise, coughing and sneezing may increase risk of Covid-19 transmission in indoor settings.

Recall that over one-half of Covid-19 transmissions are due to asymptomatic individuals.5 In this setting and in the presence of factors discussed above, it’s easy to see how transmission of Covid-19 in indoor settings can occur readily, possibly explaining cases without apparent source.

Bonus Pearl: Did you know that the odds of Covid-19 transmission may be 18.7 times greater indoors compared to open-air environment and the odds of superspreading event in closed environments may be 32.6 times higher?4

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References

  1. Bahl P, Doolan C, de Silva C, et al. Airborne or droplet precautions for health workers treating coronavirus disease 2019? J Infect Dis 2020. Published online April 16, 2020. https://pubmed.ncbi.nlm.nih.gov/32301491/
  2. Jones NR, Quereshi Z, Temple RJ, et al. Two metres or one: what is the evidence for physical distancing in covid-19? BMJ 2020;370:m3223. https://www.bmj.com/content/370/bmj.m3223/rr-18
  3. Johansson MA, Quandelacy TM, Kada S, et al. SARS-CoV-2 transmission from people without COVID-19 symptoms. JAMA Network open. 2021;4():e2035057. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2774707?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=010721
  4. Nishiura H, Oshitani H, Kobayashi T, et al. Closed environments facilitate secondary transmission of coronavirus disease 2019 (COVID-19). MedRxiv 2020. https://www.medrxiv.org/content/10.1101/2020.02.28.20029272v2.full.pdf
  5. Leclerc QJ, Fuller NM, Knight LE,e tal. What settings have been linked to SARS-CoV-2 transmission clusters? Wellcome Open Research October, 2020. https://wellcomeopenresearch.org/articles/5-83    

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Beyond masks and hand hygiene, what factors impact transmission of Covid-19 in indoor gatherings?

What’s the connection between break rooms and transmission of Covid-19 in health care settings?

Emerging data suggest that healthcare workers (HCWs) may be at increased risk of Covid-19 in break rooms when consuming food or when in the presence of others without a mask.1-4

In a study of over 700 HCWs screened for SARS-CoV-2 by PCR at a university hospital, staying in the same personnel break room as an HCW without a medical mask for more than 15 min and consuming food within 1 meter of an HCW were significantly associated with SARS-CoV-2 infection.1 Consumption of food in break rooms by personnel was thereafter “forbidden” in this facility. Interestingly, 28% of infected personnel in this study lacked symptoms at the time of testing.

A recent outbreak at a Boston hospital involving both patients and HCWs months after institution of strict infection control measures (including universal masking of visitors and HCWs and PCR testing of all patients on admission) traced the outbreak to a variety of factors, including HCWs eating in crowded work rooms.2,3

A CDC study of risk factors among adults 18 years or older with Covid-19 in the community identified dining at a restaurant as significant risk factors for Covid-19.4

Transmission of SARS-CoV-2 during eating or drinking is not surprising because masks cannot be effectively worn during food consumption. Combine eating or drinking with talking, laughing and suboptimal ventilation system and we have all the elements of perfect storm for transmission of Covid-19 during food breaks.

Bonus Pearl: Did you know that, in addition to dining at a restaurant, patients with Covid-19 without known close contact with infected persons have reported higher likelihood of going to bar/coffee shop? 4

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References

 

  1. Celebi G, Piskin N, Beklevic AC, et al. Specific risk factors for SARS-CoV-2 transmission among health care workers in a university hospital. Am J Infect Control 2020;48:1225-30. https://pubmed.ncbi.nlm.nih.gov/32771498/
  2. Freyer FJ. Brigham and Women’s hospital completes investigation of coronavirus outbreak. Boston Globe, October 19, 2020. https://www.bostonglobe.com/2020/10/19/metro/brigham-womens-hospital-completes-investigation-coronavirus-outbreak/
  3. Freyer FJ. At the Brigham, “battle-weary” staff may have allowed virus to slip in. Boston Globe, September 24, 2020. https://www.bostonglobe.com/2020/09/24/metro/brigham-womens-hospital-reports-cluster-10-covid-19-cases/
  4. Fisher KA, Tenforde MW, Felstein LR, et al. Community and close contact exposures associated with COVID-19 among symptomatic adults ≥18 years in 11 outpatient health care facilities—United States, July 2020. MMWR 2020;69:1258-64. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7499837/

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliates. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

 

 

What’s the connection between break rooms and transmission of Covid-19 in health care settings?