COVID-19：一个关于在社区中佩戴口罩的讨论

《柳叶刀》（The Lancet）发表评论，围绕是否需要在社区中佩戴口罩展开讨论。文章认为，保持社交距离和洗手是目前防控期间最重要的措施，而戴口罩可以控制传染源，从而可以对上述措施进行补充。对于不能待在家的必要工作人员来说，大规模佩戴口罩将是保护他们的重要措施。随着人们重返工作岗位，大规模佩戴口罩或将有助于减少病毒传播。

随着2019冠状病毒病（COVID-19）大流行的发展，一个相关的讨论随之展开：是否需要在社区佩戴口罩。世卫组织（WHO）在2020年1月首次提出关于佩戴口罩的指导意见，我们已经强调过其中的不一致之处。[1, 2] WHO在2020年4月6日提出的临时指导意见中，仍未建议健康人群通过在社区内广泛使用口罩（mass masking，大规模佩戴口罩）来预防严重急性呼吸综合征冠状病毒2型（SARS-CoV-2）感染。[3] 英国公共卫生部（Public Health England, PHE）的意见与之相似。[4] 但现在美国疾病预防控制中心（Centers for Disease Control and Prevention, CDC）建议民众在公共场合佩戴布制口罩[5]，加拿大、韩国以及捷克共和国等许多国家也同样要求或建议居民在公共场所佩戴口罩。[6-8] 一项基于证据的综述[9]和分析[10]支持在此次大流行中大规模佩戴口罩。有消息称，WHO和PHE正在重新审视这个问题。

通常，人们通过佩戴口罩来保护自己，但我们是基于控制传染源这个更有力的公共卫生基本原理，建议通过佩戴口罩来避免他人接触呼吸道飞沫。由于SARS-CoV-2可能无症状传播，这种方法就显得尤为重要。[13] 由于WHO、PHE等组织认为目前并无证据表明佩戴口罩可以预防包括SARS-CoV-2在内的呼吸道病毒感染，因而尚未建议大规模佩戴口罩。[3, 4] 此前关于非医疗环境中使用口罩的研究关注的是口罩在流感或类似流感的疾病环境中对佩戴者的保护作用。[14] 这些研究的设计并未评估整个人群使用口罩的效果。在疾病大流行时期人们佩戴口罩的依从性足够高，可以进行有效性评估，但是尚没有研究在大流行时期开展过调查。但是，缺少大规模佩戴口罩有效性的临床试验证据不代表戴口罩无效。从物理角度，我们支持通过遮挡口部来减少呼吸道飞沫传播，咳嗽礼仪也是出于对这部分因素的考量，而不是基于临床试验证据。[14] 2019年，WHO召开的研讨会评估了关于通过使用口罩降低大流行性流感风险和影响等非药物性公共卫生措施的证据。研讨会总结称，尽管尚无有效性试验的证据表明佩戴口罩可以减少传播，“但从物理角度来说，佩戴口罩这一举措是可能有效的”，并建议应在严重的流感大流行时期考虑在公共场合使用口罩。[15] 我们认为，如果因为没有临床试验证据表明有效，就认为大规模佩戴口罩等低成本的干预措施无效且不予考虑，将可能造成伤害。

另一个令人担忧的问题是社区口罩供应不足。医用口罩必须为医护人员保留。然而，我们认为，若只是为了控制传染源而非自我保护，那么正如美国CDC建议的那样[5]，布制口罩可能就足够了，尤其是每个人都戴口罩的话。布制口罩很容易在家里自制，清洗后还可以重复使用。相关组织机构同样担心民众能否正确佩戴、摘取以及处理口罩，但这些操作可以通过公共教育来学习。

最后，有人担心，戴口罩可能产生与保持社交距离、洗手等其他控制传染方法相关的安全错觉。我们并未发现任何实证证据表明戴口罩会导致民众忽视其他控制传染的方法。然而，即使人们选择佩戴口罩，仍需要向他们强调这一点的重要性。

大规模佩戴口罩符合基本公共卫生原则，而政府或公众目前也许还不能充分认识到这一点。首先，控制传染源（戴口罩）至少与阻断传播途径（洗手）一样重要。大规模佩戴口罩给人群带来的益处也可以被理解为一种所谓的预防悖论，即为个体带来的益处不大但却能为群体带来巨大收益的干预措施。[16] 系好安全带就是如此。此外，与接种疫苗后的群体免疫类似，只有大多数人都戴上了口罩，才能在社区内显著降低感染人数。最后，戴口罩可以类比于安全驾驶：如果我们安全驾驶，那么道路上的其他人就会从中受益；当所有人都安全驾驶时，道路交通事故的风险就会降低。

保持社交距离和洗手是目前防控期间最重要的措施。我们认为，戴口罩可以控制传染源，从而可以对上述措施进行补充。对于不能待在家的必要工作人员来说，大规模佩戴口罩将是保护他们的重要措施。随着人们重返工作岗位，大规模佩戴口罩或将有助于减少病毒传播。韩国和中国香港已经成功地在未采取限制措施的情况下控制了COVID-19暴发。[17, 18]很难评价大规模检测、严格密切接触者追踪、严格隔离等多种措施在疫情防控方面的贡献，但上述两个地区都普遍采用了公共场合佩戴口罩这一措施。由于没有有效的COVID-19疫苗，COVID-19大流行将很可能继续发展，我们希望能够在接下来的疫情阶段中考虑大规模佩戴口罩这一措施。[19] 最后，该措施也有助于控制未来的流感流行。

我们认为，在COVID-19大流行期间，通过大规模佩戴口罩控制传染源是一种廉价、高效的防控手段，可以作为社交隔离和洗手的补充。这项措施将重点从自我保护转移到利他行为，推动每个公民积极参与，也象征着全球在应对疾病大流行背景下的社会团结。END

We declare no competing interests.

*Kar Keung Cheng, Tai Hing Lam, Chi Chiu Leung [e-mail]

Institute of Applied Health Research, University of Birmingham B15 2TT, UK (KKC); School of Public Health. The University of Hong Kong, Hong Kong, Special Administrative Region, China (THL); and Hong Kong Tuberculosis, Chest and Heart Diseases Association, Hong Kong, Special Administrative Region, China (CCL)

参考文献（上下滑动查看）

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7 Government of Canada. Considerations in the use of homemade masks to protect against COVID-19. Notice to general public and healthcare professionals. 2020. https://www.canada.ca/en/health-canada/services/drugs-health-products/medical-devices/activities/announcements/covid19-notice-home-made-masks.html (accessed April 15, 2020).

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*中文翻译仅供参考，所有内容以英文原文为准。

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