The results of our study support a two-pronged approach aimed at significantly reducing the passage of pathogens without the practical impossibility of a travel ban or population-wide screening. We propose: (1.) the identification of communities at risk, defined by, (a.) environmental isolation, which represents a huge medical evacuation budget, (b.) the need for work, which represents an increase interactions and opportunities for transmission from both intra-environmental (on-site) and labor influx (travellers), and (c.) healthcare limitations, due to economic feasibility and geographic, driving distance from solid access to health care; and (2.) multifactorial preventions that include (a.) questionnaires probing for exposure potential and symptoms (one screening trip to AD 48 h before, and one to AD before social distancing, in waiting for RT-PCR results), (b.) basic prevention precautions, such as wearing masks and washing hands, (c.) temperature checks (at DA and in other congested areas, such as the on-site cafeteria), (d.) RT-PCR screening at AD labs, and (e.) social distancing, isolation and quarantine protocol.
Separately, the different facets of prevention have individual effectiveness. For example, according to this study, the AD questionnaire alone would have prevented two of the 13 individuals (15.4%) from boarding the plane, because case no. 11 and case no. 13 reported either symptoms, or recent contact with a confirmed case of COVID-19 at the time of boarding. The prescreening form to be completed by travelers 24 to 48 hours before boarding would ensure that people with symptoms or in contact with a confirmed case would be referred to the public health system (and remain outside our data from swab samples). The AD questionnaire provides additional screening coverage between the pre-screening form (one to two days before) and pre-boarding on the same day. An added benefit of the AD questionnaire as part of the pre-boarding swab appears to be that individuals pay greater attention to symptoms and potential exposure when completing this questionnaire, aware of upcoming lab tests. (as has been voluntarily reported by individuals).
Although screening and AD questionnaires are excellent tools for mitigating infectious spread, the example of case 12 illustrates the need for RT-PCR screening, because the worker failed to reveal in the questionnaire his return from international travel the day before boarding. for site A. Specific information would have instituted a 14-day quarantine or isolation upon return to Canada, per federal regulations at the time8. The absence of signs and symptoms, including elevated temperature, shows the value of RT-PCR in reducing the movement of asymptomatic individuals capable of causing an outbreak. Even so, one individual, Case #7, passed all AD screening tests, including RT-PCR. This case may represent a small fraction of asymptomatic carriers in the prodromal period when the virus is below the detection level of laboratory tests, although a false negative cannot be ruled out. Likely due to early detection at the mine site and subsequent isolation, along with other basic health protocols, Case #7 did not induce detectable spread of SARS-CoV-2 from health care workers and the site A laboratory. Future studies to assess the effectiveness of transmission prevention should consider the addition of serological surveys when economically and functionally acceptable.
Our study found lower screening violation by prodromal asymptomatic carriers (1 in 13) than the 44% projected by other models, which translates to 5-6 expected individuals.9. Even so, several factors should be considered as mitigating the comparisons: (1.) Our study is limited by the low number of reported cases (13) out of 15,873 samples tested; (2.) Mine workers were in a culture of continuous screening and may have been more rigorous with health safety measures; (3.) The 24-48 h pre-travel screening questionnaire resulted in a waiting period for people who recognized the risk of exposure, including travel, thus exceeding the typical prodromal period of 2.4 days during AD screening9; and (4.) Our data comes from a uniformity of process rather than an amalgamation of disparate sites and processes. Furthermore, comparisons of data unrelated to asymptomatic prodromal rupture are largely flawed, especially for sites testing much larger groups of symptomatic individuals, such as hospitals and national referral centers.
Although no secondary transmissions were detected at either mine site in December 2021, Case #9 was associated with Case #10 due to proximity to in-flight seating. This potential exposure pathway is now mitigated by the revised protocol whereby boarding occurs after the return of RT-PCR data. Overall, the current report supports the use of diagnostic laboratories at travel points to provide an additional contribution to other control measures. Although the costs of implementing these measures were entirely borne by the private mining company; the laboratory costs and scientific expertise of the screening process remained low, having been conducted by a non-profit organization. Even so, companies and organizations bearing the expense of these combined testing measures should weigh those costs against the expense of spreading the pandemic and the associated medical response and industry shutdown, without talk about the ethical implications of using lesser safety precautions.