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非典十年后,港人摘下口罩

非典十年后,港人摘下口罩

David Whitford 2013-03-12
“非典”爆發(fā)十年后,香港人已不像以前那樣常在公共場(chǎng)合戴醫(yī)用口罩了。問(wèn)題是:戴口罩真的能預(yù)防呼吸系統(tǒng)疾病的傳播嗎?

????“非典”疫情已過(guò)去整整十年。十年前,SARS曾造成全球8,000多人感染,774人死亡。亞洲各大城市隨處可見(jiàn)戴口罩出行的人。

????當(dāng)時(shí)香港共299人死亡,是中國(guó)境內(nèi)疫情最嚴(yán)重的城市。然而,近日香港大學(xué)民意研究計(jì)劃的調(diào)查結(jié)果表明,港人防疫意識(shí)已逐漸松懈。只有一半的受訪者表示,他們會(huì)在傷風(fēng)感冒時(shí)在公共場(chǎng)所戴口罩?!队⑽幕?bào)》(The Standard)援引一位傳染病專(zhuān)家的話(huà)表示,這一調(diào)查結(jié)果“令人擔(dān)憂(yōu)”。

????不過(guò)說(shuō)到戴口罩,專(zhuān)家們的意見(jiàn)并不一致。調(diào)查結(jié)果發(fā)布后第二天,我拜訪了香港衛(wèi)生署衛(wèi)生防護(hù)中心感染控制科學(xué)委員會(huì)前主席司徒永康博士,對(duì)他進(jìn)行了為期一小時(shí)的采訪。采訪的氣氛很熱烈,之所以這么說(shuō),是因?yàn)樗就讲┦恐v起話(huà)來(lái)太激昂了,以至于他的助手來(lái)敲了兩次門(mén),懇請(qǐng)他小聲點(diǎn),因?yàn)槌车搅烁舯诘娜?。后?lái)我們到外面去了。

????司徒博士的觀點(diǎn),一言以蔽之就是:“這簡(jiǎn)直太蠢了!”他說(shuō),要想保護(hù)自己和他人,完全可以采取更好、更簡(jiǎn)單的方式。他承認(rèn),戴口罩有時(shí)候確實(shí)有些用處,“但是使用方法不當(dāng)反而有害!”

????司徒博士表示,要想了解“非典”、新冠狀病毒等癥狀類(lèi)似流感的呼吸系統(tǒng)疾病,首先要知道的是,它們從技術(shù)上講并不是通過(guò)空氣傳播的疾病 :“很多年以前,我剛做醫(yī)生那陣子,大家都認(rèn)為所有呼吸道疾病都是通過(guò)空氣傳播的,因?yàn)?,”說(shuō)到這里,他咳嗽了一聲,作為示范,“你咳出來(lái)的東西都散播到空氣中去了?!?/p>

????那么,咳嗽時(shí)會(huì)產(chǎn)生哪些噴出物呢?司徒博士表示,噴出物包括大粒子,還有飛沫,大飛沫很快就掉落到地上,不會(huì)飛出一米遠(yuǎn)。只有足夠小的粒子才可以在空氣中傳播。這種傳染性的小飛沫有個(gè)專(zhuān)門(mén)的術(shù)語(yǔ),叫做氣溶膠。美國(guó)疾病控制中心和世界衛(wèi)生組織都認(rèn)為,只有三種常見(jiàn)傳染病會(huì)在患者咳嗽或者出皮疹時(shí)產(chǎn)生氣溶膠?!胺谓Y(jié)核,知道吧?”司徒博士說(shuō),“還有水痘。還有麻疹。沒(méi)了,就這么三種!”

????香港科技大學(xué)健康、安全及環(huán)境處處長(zhǎng)關(guān)繼祖博士并不同意這個(gè)觀點(diǎn)。他不是醫(yī)生,而是工程師。他說(shuō):“任何工程師,只要研究了患者咳嗽時(shí)噴出氣溶膠的機(jī)制,就會(huì)毫不猶豫地告訴你,不管是咳嗽還是打噴嚏,都會(huì)產(chǎn)生多分散氣溶膠?!币簿褪钦f(shuō)粒子的大小各不相同。他承認(rèn)大粒子會(huì)掉落在地,但小粒子會(huì)滿(mǎn)天飛散。關(guān)博士表示,把安全距離設(shè)定為一米,而不考慮實(shí)際情況,“肯定不是對(duì)公共衛(wèi)生最有利的選擇?!?/p>

????司徒博士對(duì)此嗤之以鼻?!笆姓f(shuō)要定成兩米,”他說(shuō),“我們不同意。你定成兩米了,醫(yī)院就要花費(fèi)很多成本,而且這個(gè)標(biāo)準(zhǔn)還沒(méi)有被證實(shí)。一米就夠了!了解了這一點(diǎn),事情就很簡(jiǎn)單了!”

????It has been exactly 10 years since the deadly SARS outbreak that infected more than 8,000 people worldwide, killed 774, and made surgical masks a common sight in cities across Asia.

????Hong Kong, where 299 died, was the second-hardest hit in the world after China, and the University of Hong Kong Public Opinion Programme recently released the results of a survey suggesting that Hongkongers had grown dangerously complacent. Barely half of the respondents claimed they bother to wear a mask in public anymore if they have a cold or the flu. One infectious diseases expert quoted in the Hong Kong daily, The Standard, described the results as "alarming."

????But when it comes to masks, the experts don't all agree. The day after the survey was published, I spent a boisterous hour with Dr. Wing-hong Seto, former chairman of the Scientific Committee on Infection Control at the Centre for Health Protection, Department of Health, Hong Kong. I say boisterous because he got so animated during our interview that twice his handler knocked on the door and asked him to keep it down, please, because he was bothering the people in the next room. Eventually we moved outdoors.

????Dr. Seto's bottom line: "This is so stupid!" He says there are better, simpler ways to protect yourself and others. A mask might help, he allows, sometimes, "but if not used properly it will hurt you more than help!"

????The first fact to understand about SARS, as well as the new coronavirus and other respiratory conditions that produce flu-like symptoms, Dr. Seto says, is that they are not, technically speaking, airborne diseases: "Years ago, when I first became a doctor, we used to think that all chest infections were transmitted airborne, because" -- he coughs now, demonstrating -- "you cough into the air."

????But what comes out when you cough? Large particles, he says; wet, heavy droplets that fall to the floor within one meter of your mouth. To go airborne the particles must be very small. The term for small-particle infectious spray is aerosol, and both the U.S. Centers for Disease Control and the World Health Organization agree that there are only three diseases active among humans that produce aerosol, by cough or by rash. "TB, okay?" says Dr. Seto. "Chickenpox. And measles. Full stop. That's it!"

????Dr. Joseph Kwan, director of Health, Safety, and Environment across town at Hong Kong University of Science and Technology, disagrees. He's not a medical doctor, he's an engineer, and he says, "engineers who have actually studied the mechanism of aerosol emission from coughing patients would readily tell you that any cough or sneeze, they are essentially poly-dispersed." This means the particles are different sizes. Big particles drop, he admits, but smaller ones can fly. To apply the one-meter rule indiscriminately, Dr. Kwan argues, "certainly is not in the best interests of public health."

????Dr. Seto just scoffs. "City says two meters," he acknowledges. "We disagree. You make it two meters, it costs a lot of money for hospitals, and it's not proven. One meter is all you need! If you understand this, things become very simple!"

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