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Face-masks and covid-19
口罩和新冠
Helpful humidity
有用的濕度
As well as filtering air, face-masks may boost the immune system
口罩除了過濾空氣，還可以增強免疫系統(tǒng)
Face-masks help reduce the spread of SARS-COV-2, the virus that causes covid-19. Several studies have reported the more surprising finding that, even if wearers do become infected, their disease is usually milder. Now Joseph Courtney and Ad Bax, a pair of researchers at the National Institutes of Health in Bethesda, Maryland, think they may have worked out why. As they report in the Biophysical Journal, it comes down to humidity, the immune system, and the protective powers of mucus.
口罩有助于減少導致新冠的SARS-COV-2(新型冠狀病毒)的傳播。一些研究報告了更為驚人的發(fā)現(xiàn)：即使口罩佩戴者被感染了，他們的癥狀通常也比較輕。目前，馬里蘭州貝塞斯達國家衛(wèi)生研究院的兩位研究員約瑟夫·考特尼和艾德·巴克斯認為他們可能已經(jīng)找到了原因。他們在《生物物理學雜志》上發(fā)表的報告稱，這歸結為濕度、免疫系統(tǒng)和黏液的保護能力。
At first glance, there may not seem much of a mystery to unravel. Masks cut the number of infectious particles entering the nose and mouth. One might expect, therefore, that severe disease would be less likely. But it is not so. One vital factor which predicts disease severity is how far viral particles make it into a person's lungs. Cheap cotton face-masks struggle to block the smallest aerosols, which are the most likely to penetrate deeply. Dr Courtney and Dr Bax wondered if something else might explain their protective effect.
乍一看似乎沒有什么神秘的事物需要揭開。口罩可以減少進入口鼻的傳染性顆粒，因此人們可能會認為感染嚴重疾病的可能性會降低。但事實并非如此。預測疾病嚴重程度的一個重要因素是病毒顆粒進入人體肺部的距離。廉價的棉質口罩很難阻擋最小的懸浮微粒，而這些懸浮微粒最有可能滲透到深處。考特尼博士和巴克斯博士想探究是否有其他原因可以解釋它們的保護作用。
One of the body's first lines of defence against airborne pathogens is known as the "mucociliary clearance mechanism". Sticky mucus in the nose and respiratory tract snares viruses and bacteria. Little hairs known as cilia push the mucus into the throat. From there it is swallowed and potent stomach acids destroy the invaders. But this mechanism relies on the relevant body parts staying moist.
人體抵抗空氣傳播病原體的第一道防線被稱為“黏液纖毛清除機制”。鼻子和呼吸道里黏黏的粘液會吸引病毒和細菌，被稱為纖毛的細小毛發(fā)會將粘液推入喉嚨，粘液在喉嚨處被吞下，之后強有力的胃酸摧毀入侵者。但這一機制依賴于一點：相關身體部位要保持濕潤狀態(tài)。
That is harder in winter, for as air gets colder, its capacity to hold waterfalls. Lower humidity tends to dry out the respiratory tract. This is one reason why many upper-respiratory viruses, such as influenza, flourish in the winter.
在冬天更難，因為隨著空氣變冷，它容納水分的能力會減弱。濕度較低會使呼吸道變得干燥。這就是許多上呼吸道病毒(如流感病毒)在冬季肆虐的原因之一。
Dr Courtney and Dr Bax speculated that masks may help keep things damp. They reasoned that, as a person exhales, water vapour would condense on the inside of a mask. Then, upon inhalation, dry air passing through the mask would collect the deposited water and bring it back into the respiratory tract and lungs. That could be handing a mask-wearer's immune system a significant advantage.
考特尼博士和巴克斯博士推測，口罩可能具備保持濕潤的功效。他們推斷，當一個人呼氣時水蒸氣會在口罩內(nèi)部凝結，被吸入后通過口罩的干燥空氣會收集積水并將其帶回呼吸道和肺部。這可能會給戴口罩者的免疫系統(tǒng)帶來很大的好處。
Keen to test their idea, the researchers checked several masks at 37°C, 22°C and 8°C. They breathed into a sealed box packed with sensitive instruments, and worked out humidity levels in their upper respiratory tracts. They found that, although all masks increased humidity levels to some extent, the heavy cotton mask did best of all. In the hottest room it boosted the relative humidity of inspired air by over 50%, compared with breathing without a mask. In the cold room, that number rose to 300%. (The other masks recorded figures of between 150% and 225%.) That suggests that, besides filtering out at least some of the viral particles floating about in the air, masks help keep a person's snot levels healthily high.
為了驗證他們的想法，研究人員在37°C、22°C和8°C的溫度下檢驗了幾種口罩。他們向一個密封的盒子里呼氣，盒子里裝滿了敏感的儀器，然后計算出他們上呼吸道的濕度。他們發(fā)現(xiàn)，雖然所有的口罩都在一定程度上增加了濕度，但厚重的棉質口罩效果最好。在最熱的房間里，戴棉質口罩呼吸與不戴口罩呼吸相比，它使吸入空氣的相對濕度提高了50%以上。在寒冷的房間里這一數(shù)字上升到了300%。(其他口罩的記錄數(shù)字在150%至225%之間。)這表明，口罩除了能過濾掉空氣中漂浮的部分病毒顆粒外，還能讓人的鼻涕保持在非常高的健康水平。
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