key: cord-0908897-0ygaj2hm
authors: Lan, F.-Y.; Wei, C.-F.; Hsu, Y.-T.; Christiani, D. C.; Kales, S. N.
title: Work-related Covid-19 transmission
date: 2020-04-11
journal: nan
DOI: 10.1101/2020.04.08.20058297
sha: b00b18736affc081f792079aca15257c3f621299
doc_id: 908897
cord_uid: 0ygaj2hm

Importance: Our study helps fill the knowledge gap related to work-related transmission in the emerging coronaviral pandemic. Objective: To demonstrate high-risk occupations for early coronavirus disease 2019 (Covid-19) local transmission. Methods: In this observational study, we extracted confirmed Covid-19 cases from governmental investigation reports in Hong Kong, Japan, Singapore, Taiwan, Thailand, and Vietnam. We followed each country/area for 40 days after its first locally transmitted case, and excluded all imported cases. We defined a possible work-related case as a worker with evidence of close contact with another confirmed case due to work, or an unknown contact history but likely to be infected in the working environment (e.g. an airport taxi driver). We calculated the case number for each occupation, and illustrated the temporal distribution of all possible work-related cases and healthcare worker (HCW) cases. The temporal distribution was further defined as early outbreak (the earliest 10 days of the following period) and late outbreak (11th to 40th days of the following period). Results: We identified 103 possible work-related cases (14.9%) among a total of 690 local transmissions. The five occupation groups with the most cases were healthcare workers (HCWs) (22%), drivers and transport workers (18%), services and sales workers (18%), cleaning and domestic workers (9%) and public safety workers (7%). Possible work-related transmission played a substantial role in early outbreak (47.7% of early cases). Occupations at risk varied from early outbreak (predominantly services and sales workers, drivers, construction laborers, and religious professionals) to late outbreak (predominantly HCWs, drivers, cleaning and domestic workers, police officers, and religious professionals). Conclusions: Work-related transmission is considerable in early Covid-19 outbreaks, and the elevated risk of infection was not limited to HCW. Implementing preventive/surveillance strategies for high-risk working populations is warranted.

Introduction workers (HCWs). Work-related transmission among HCWs constituted a large 23 proportion in previous coronavirus outbreaks. HCWs comprised 37-63% of 24 suspected severe acute respiratory syndrome (SARS) cases in highly affected 25 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. In contrast, there is limited discussion on the work-related risks among 6 workers such as taxi drivers, tour guides, cleaners and janitors, and civil 7 servants, who have frequent contact with the public in their daily routines or 8 have workplaces with higher risks of virus exposure [14] . 9 10 In this study, we aimed to identify the occupations at higher risk of Covid-19 11 transmission, and to explore the temporal distribution of work-related cases 12 among local transmission. 

Study population selection 16 We extracted and included all locally transmitted Covid-19 confirmed cases 17 from the publicized government investigation reports from six Asian 18 countries/areas, including Hong Kong, Japan, Singapore, Taiwan, Thailand, 19 and Vietnam. These countries/areas were selected since they shared some 20 common temporo-spatial characteristics. First, they are proximal to Mainland 21 China, where the first outbreak of Covid-19 was reported. Second, the first 22 cases of these countries/areas were imported cases from Mainland China in 23 mid-January. Third, the first locally transmitted cases in these countries/areas 24 were identified around late January to early February. We followed each 25 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint country/area for forty days since the report of the first locally transmitted case 1 and excluded the imported cases. The study population selection process is 2 presented in Fig. 1 to the jobs similarity. 24 All differences between the occupation physicians were reviewed by the third 25 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint investigator, who is a physician-epidemiologist to reach a consensus. We also conducted sensitivity analysis comparing the results between the six 21 countries/areas and five countries/areas excluding Japan. We excluded Japan 22 due to its different case reporting system from other countries/areas. Unlike 23 other countries/areas that have central reporting systems, Japan had cases 24 reported from each prefecture separately. Differences in reporting 25 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. and so on. In terms of occupation grouping, the groups with the most cases 20 were HCWs, drivers and transport workers, services and sales workers, 21 cleaning and domestic workers, and public safety workers. (Table 1) 22 23 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. In further sensitivity analysis excluding Japan because of its different case 21 reporting system, the daily confirmed local transmissions became relatively 22 constant (Fig. 2B) . After excluding Japan, possible work-related cases 23 comprised 44% of the locally transmitted cases in the early period, while only 24 18% in the late period (Chi-squared statistic=18.8, P-value<0.0001).

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint 1 HCW comprised 22% of the possible work-related cases. Moreover, we found 2 the occurrence of Covid-19 transmission among the HCW was relatively late 3 compared to the non-HCW population. Fig. 2(A) and Fig. 2(B) CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint non-HCW comprised the majority of the possible work-related cases and most 1 of the cases were not able to trace back the infection sources. are more likely to be exposed to contaminated surfaces than direct contact 15 with Covid-19 patients [18] . 16 17 In this study, the proportion of HCWs among locally transmitted cases was 18 smaller than non-HCWs in the included countries/areas, 3% versus 12% 19 respectively. The first cases HCWs appeared much later than the first non- CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . in the non-healthcare workplaces to protect the workers in this pandemic [27] . 1 Early delivery of infection control knowledge and health concepts to workers, 2 as well as providing adequate PPE are crucial in protecting workers and the 3 whole society. should be non-differential as the official reports were not different between 24 whether a case was work-related or not. Third, the criteria of deciding whom 25 . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint to be tested varied between countries/areas, especially during early outbreaks 1 when testing capacities were limited. Therefore, high risk populations, 2 including high risk occupations, might tend to be tested. However, we believe 3 the bias was non-differential, as health authorities should not decide whom to 4 be tested differently based on whether the suspected case was a worker or 5 not. In fact, most of the early cases were tested because of the symptoms or CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted April 11, 2020. is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint Figure 1 . Study population selection process . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted April 11, 2020. . https://doi.org/10.1101/2020.04.08.20058297 doi: medRxiv preprint

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