看一下中國的一些討論。一般是引用馬裏蘭大學一個教授的試驗。
https://www.thepaper.cn/newsDetail_forward_5872421
下麵有這個試驗的摘要。
我簡單看了一下這個研究項目。收集的呼吸氣中病毒，是要求參加試驗的病人坐30分鍾，通過一個緊套在病人麵部上的設備收集。
142個病人，有218個樣品。52個發現病毒。如果這樣，應該是23.9%，而不是下麵的39%。或者是52個病人的樣品中發現病毒？
其實，對這個研究項目的設計是有問題的。如果懷疑正常呼出氣中有病毒，不需要坐30分鍾收集。隻要放在鼻子下收集就可以了。對於流感患者，坐30分鍾，很可能會有噴嚏或咳嗽，這樣收集到的呼吸氣事實上就不是正常的呼吸氣了。由於並不是所有或大部分呼吸氣樣品都有病毒，更說明，正常呼吸氣中大部分情況應該並沒有病毒。
AAbstract
Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission. We screened 355 symptomatic volunteers with acute respiratory illness and report 142 cases with confirmed influenza infection who provided 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse >5-µm and fine ≤5-µm fractions) on days 1–3 after symptom onset. We assessed viral RNA copy number for all samples and cultured NP swabs and fine aerosols. We recovered infectious virus from 52 (39%) of the fine aerosols and 150 (89%) of the NP swabs with valid cultures. The geometric mean RNA copy numbers were 3.8 × 104/30-minutes fine-, 1.2 × 104/30-minutes coarse-aerosol sample, and 8.2 × 108 per NP swab. Fine- and coarse-aerosol viral RNA were positively associated with body mass index and number of coughs and negatively associated with increasing days since symptom onset in adjusted models. Fine-aerosol viral RNA was also positively associated with having influenza vaccination for both the current and prior season. NP swab viral RNA was positively associated with upper respiratory symptoms and negatively associated with age but was not significantly associated with fine- or coarse-aerosol viral RNA or their predictors. Sneezing was rare, and sneezing and coughing were not necessary for infectious aerosol generation. Our observations suggest that influenza infection in the upper and lower airways are compartmentalized and independent.
