Background: SARS-CoV-2 epidemiology implicates airborne transmission; aerosol infectiousness and impacts of masks and variants on aerosol shedding are not well understood. Methods: We recruited COVID-19 cases to give blood, saliva, mid-turbinate and fomite (phone) swabs, and 30-minute breath samples while vocalizing into a Gesundheit-II, with and without masks at up to two visits two days apart. We quantified and sequenced viral RNA, cultured virus, and assayed sera for anti-spike and anti-receptor binding domain antibodies. Results: We enrolled 49 seronegative cases (mean days post onset 3.8 plus-minus 2.1), May 2020 through April 2021. We detected SARS-CoV-2 RNA in 45% of fine (less-than-or-equal 5 micron), 31% of coarse (>5 micron) aerosols, and 65% of fomite samples overall and in all samples from four alpha-variant cases. Masks reduced viral RNA by 48% (95% confidence interval [CI], 3 to 72%) in fine and by 77% (95% CI, 51 to 89%) in coarse aerosols; cloth and surgical masks were not significantly different. The alpha variant was associated with a 43-fold (95% CI, 6.6 to 280-fold) increase in fine aerosol viral RNA, compared with earlier viruses, that remained a significant 18-fold (95% CI, 3.4 to 92-fold) increase adjusting for viral RNA in saliva, swabs, and other potential confounders. Two fine aerosol samples, collected while participants wore masks, were culture-positive. Conclusion: SARS-CoV-2 is evolving toward more efficient aerosol generation and loose-fitting masks provide significant but only modest source control. Therefore, until vaccination rates are very high, continued layered controls and tight-fitting masks and respirators will be necessary.

中文翻译：

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早期轻度感染期间呼出气溶胶中的传染性 SARS-CoV-2 和口罩的功效

背景：SARS-CoV-2 流行病学涉及空气传播；气溶胶传染性以及口罩和变体对气溶胶脱落的影响尚不清楚。方法：我们招募了 COVID-19 病例，分别在两天内最多两次就诊时向 Gesundheit-II 发出血液、唾液、中鼻甲和污染物（电话）拭子，以及 30 分钟的呼吸样本. 我们对病毒 RNA、培养的病毒和抗刺突和抗受体结合域抗体的血清进行了量化和测序。结果：我们招募了 2020 年 5 月至 2021 年 4 月的 49 例血清阴性病例（发病后平均天数为 3.8 加减 2.1）。我们在 45% 的罚款（小于或等于 5 微米）中检测到 SARS-CoV-2 RNA， 31% 的粗（> 5 微米）气溶胶和 65% 的污染物样本，以及来自四个 α 变体案例的所有样本。口罩在细气溶胶中将病毒 RNA 减少了 48%（95% 置信区间 [CI]，3% 至 72%），在粗气溶胶中减少了 77%（95% CI，51% 至 89%）；布口罩和外科口罩没有显着差异。与早期病毒相比，α 变体与细气溶胶病毒 RNA 增加 43 倍（95% CI，6.6 至 280 倍）相关，但仍显着增加 18 倍（95% CI，3.4 至 92 倍） ) 增加对唾液、拭子和其他潜在混杂因素中病毒 RNA 的调整。在参与者戴口罩时收集的两个精细气溶胶样本为培养阳性。结论：SARS-CoV-2 正在朝着更有效的气溶胶生成方向发展，宽松的口罩提供了重要但仅适度的源控制。因此，在疫苗接种率非常高之前，持续的分层控制和紧密贴合的口罩和呼吸器将是必要的。