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专访剑桥传染病专家:新冠传染性比SARS强,跨物种传染病爆发频率在增高


2月10日,世界卫生组织将自去年12月在中国首次确认的新型冠状病毒,正式命名为“Covid-19”。世卫组织总干事谭德塞在新闻发布会上表示,之所以如此命名,是希望不涉及任何特定地域、人或群体,因为该病毒是全人类共同的敌人,并呼吁世界各国抓住当前可贵的“窗口期”,猛烈打击该病毒,全球合作共同抗疫,以防止其在全球范围内的大蔓延。

全球合作抗疫的行动中,英国科研界也正在加大对新型冠状病毒的研究力度,其中包括加速对相关疫苗的研发。

近日,就新型冠状病毒肺炎疫情的严重性、爆发特点、新冠疫苗和药物的研发进展等问题,剑桥大学传染病研究中心研究员芙蕾雅·杰夫科特(Dr. Freya Jephcott)博士接受了《华闻周刊》专访。


剑桥大学传染病研究中心研究员杰夫科特博士接受《华闻周刊》专访


采访实录如下: 

《华闻周刊》:从新冠病毒(Covid-19)感染病例的死亡率和传播特性来看,你认为它所引发的疫情的严重性是否会超过SARS?

杰夫科特博士:早期的迹象表明,由Covid-19病毒引起的疾病病情通常比SARS的病情要轻。目前的大部分研究评估,都将Covid-19的病例死亡率(即已知病例的最终死亡比例)设在2%,而SARS的死亡率约为6-11%。

一些研究者认为,Covid-19病毒感染引起的疾病之所以病情相对温和,与我们常常在呼吸道疾病(例如乙型流感)中看到的“此消彼长”特点相关,即某种病毒的传染性越高,它在个体病例身上,所引发的病情严重程度就会越低。

这与某种病毒更易于附着于肺部的哪一部分有关。如果该病毒更易于附着于肺的下部,那么对于受感染的个体来说,它所引发的病情就更为严重。但是,与那些更容易附着于上呼吸道的病毒相比,它更不容易通过呼吸、打喷嚏或咳嗽传出体外,也因此更难以传播给他人。

因此,此次的新冠病毒Covid-19的传染性看上去的确比SARS更高,尽管它引发的个体病例的病情通常比后者要轻。现实中, Covid-19已感染的人数已经远超SARS,这将在事实上,使其最终带来的死亡人数的总数超过SARS。

Early indications suggest that the disease caused by Covid-19 is typically milder than what was seen with SARS. Most estimates put the case fatality ratio (that is the proportion of known cases who end up dying) at 2% for Covid-19 and around 6-11% for SARS. 

Some have suggested that the relative mildness of 2019-nCoV relates to a trade-off that is often seen with respiratory illnesses such as influenza, whereby the more infectious the virus is, the less severe the illness tends to be on an individual level.

This is related to the part of the lungs that virus is more adept at attaching to. If the virus has an affinity for the lower part of the lungs, then the illness tends to be worse for the infected individual. However, it is also less likely to spread to other people as it’s less likely to be breathed, sneezed or coughed out than a virus with an affinity for the upper respiratory tract. Certainly, 2019-nCoV does look to be more infectious than SARS even if the illness it produces is typically milder. In fact, 2019-nCoV has now infected far more people than SARS ever did, which has actually resulted in the higher overall number of deaths. 

 

《华闻周刊》:人类与野生动物(包括蝙蝠、蛇和其他物种)的接触及互动历史十分悠久。但为什么近年来,我们看到从动物到人的致命性跨物种传播疾病的爆发(例如SARS、埃博拉和此次的新冠病毒)越来越频繁?有哪些因素加速了这一进程?

杰夫科特博士:这类人畜共患疾病的爆发(即因病原体从一种动物种群跃入人类种群而引起的爆发)的频率和规模确实在增加

在考虑是哪些因素导致了这种情况时,一个有用的方法是,将此类疾病爆发的过程分为三个部分来分析:1.导致病原体或病毒在动物种群中大量传播的因素;2.导致病毒更大程度跨物种外传的因素(即导致病原体从动物种群跃入人类种群的因素);3.导致病毒在人与人之间更大传播的因素。

从此前的一系列研究中,我们已经知道,病毒常常会从动物种群跳入人类种群,但是在它们感染了最初的那个人之后,它们往往难以进一步在人类种群中传播。

虽然我们目前仍然不知道导致此次新冠病毒疫情爆发的到底是哪些确切因素的混合,但某些导致人畜共患疾病的常见驱动因素可能与这种情况有关。例如,我们知道,将各种动物尤其是野生动物混合在一起,使其在充满压力和不卫生的条件下保持紧密接触(如在活体动物市场上有时看到的那样),可以增加动物之间传播的病毒的数量和多样性,并增加病毒溢出到人类宿主中的风险。

因此,此次疫情最初爆发的那个潮湿的市场(即华南海鲜市场)的环境条件,可能在触发这次爆发的过程中,发挥了重要作用。病毒在跃入人类群体后,武汉市内人口的密集度以及该市作为中国重要的国内和国际交通枢纽的地位,可能促进了病毒的迅速传播。

The frequency and scale of these zoonotic outbreaks (outbreaks that have started because a pathogen has jumped from an animal population into a human one) do look to be increasing.

When thinking about what might be driving this, it’s perhaps useful to think about the process of these kinds of outbreaks taking place in three parts: things that lead to a greater circulation of the pathogen or virus within the animal population; things that lead to greater viral spillover (i.e. the pathogen making the jump from the animal population into the human one); and things that lead the virus to spread between humans more.  We know from a range of studies that viruses often jump from animal populations into human ones but then fail to spread much further than the person they originally infected.

Whilst we still do not know the exact mix of factors responsible for the 2019-nCoV outbreak there are some common drivers of zoonotic disease emergence that could be relevant to this situation.

For instance, we know that having a mix of species of animals, especially wild animals, kept close together in stressful and unhygienic conditions, as are sometimes seen in live animal markets, can increase the amount and diversity of viruses circulating between animal species and increase the risk of a virus spilling over into a human host. The conditions in the wet market where this outbreak is believed to have started could therefore have played an important role in triggering this outbreak. Once in the human population, the rapid spread of the virus was likely facilitated by the density of people within the city of Wuhan and the city’s status as an important national and international transport hub.


《华闻周刊》:基于现在的情况和你的判断,我们是否已进入了一个“流行病世纪”?从最近这几次传染病爆发事件中,我们有哪些教训和经验可以汲取?

杰夫科特博士:我们此前少见或未见过的疾病的出现频率和规模的确在增加。这可能是由全球化进程的一系列特性所导致的。

具体来说,全球人口数量快速增加,彼此还相互联系,人们越来越倾向于居住在人口稠密的城市中,对食用动物的兴趣也在增加。

每当在发生了重大的流行病之后,我们善于去改进疫情应急及应对方面的基础设施,但是,我们不太善于去汲取与预防和减轻疾病伤害有关的经验教训。例如,去解决我上面提到的促使疾病出现的根本性驱动因素,或者去建立起一套公共卫生基础设施的良好标准。如果有资源丰富的医疗保健设施让我们随时可用,就可以让我们对任何潜在疾病疫情的反应更容易、更便宜和更有效。

从长远来看,仅仅投资于应急性措施是行不通的,我们需要以更有实效的方式去着手解决那些更大的根本性因素和社会脆弱性问题。

The frequency and scale of outbreaks of previously rare or unseen pathogens do appear to be increasing and this is likely due to a range of features of globalisation; namely, a rapidly growing, interconnected global population, with a tendency to live in dense cities and with an ever-increasing taste for animal. We are very good at improving our reactive outbreak response infrastructure in the wake of major epidemics; however, we are not so good at learning the lessons relating to outbreak prevention and mitigation. For instance, addressing the drivers of disease emergence I listed above or ensuring a good standard of basic public health infrastructure. Things like ready access to well-resourced primary healthcare facilities can make responding to outbreaks, regardless of the underlying disease, far easier, cheaper and more effective. Simply investing in reactive responses is not going to work in the long-term so we need to start addressing these larger underlying drivers and societal vulnerabilities in a far more meaningful way.

 

《华闻周刊》:截至目前,英国已有9个新冠病毒确诊病例。而一些专家已就该疫情在全球的蔓延风险提出警告(例如,香港大学公共卫生医学教授梁卓伟警告称,该病毒如果防控不力,可能会感染世界三分之二的人口)。你对该疫情在英国和全球的扩散有何预测?我们现在还可以采取哪些措施来阻止它在全球范围内的大爆发?

杰夫科特博士:现阶段,世界卫生组织仍认为该病毒是可控的,我们有可能让疫情不在东亚以外的地区大量传播,也就是说,在该地区以外的国家,可能仅需要处理偶发的孤立案例。但是,我们已经在中国以外的国家(例如在新加坡)看到了该病毒持续的传播路径,并且在世界其他地区也已经开始出现该病毒广泛传播的风险。

由Covid-19病毒引起的疾病与其他常见的呼吸道疾病(例如普通感冒和流感)的相似性,意味着它很可能被当成这类疾病对待,尤其是在监测和测试能力有限的地方。如果该病毒在其他国家/地区确实开始广泛传播了,并且就像我说的那样,这可能已经在发生了,那么最重要的事情将是减缓该病毒的传播速度。我们可以做一些事情,比如通过让已经感染或与已知病例有过密切接触的人们在家中工作几周(有时被称为“自我隔离”),我们可以控制某段时间内被感染的病例的数量。

这么做,有可能把对卫生医疗系统造成的额外压力降至最低,并把在特定时间内无法工作的人的数量控制在一定范围内,从而避免对我们社会的供应链和能提供的各项服务造成实质性破坏。

每个国家在减缓病毒传播方面的能力存在着差异。重要的是,我们不要忽视那些中低收入的国家,因为这些中低收入国家可能缺乏来实施所有必要干预措施的可用资源,它们现存的卫生系统往往已经是捉襟见肘,这类传染病的爆发,给它们带来的后果将是更为严重的。

At present its sounds as though the World Health Organization still thinks it is possible that the outbreak might able to be brought under control without significant spread of the disease outside of East Asia. This would mean that countries outside of the region will only have to occasionally deal with an isolated introduced case or two. However, we are already seeing on-going transmission in countries outside of China, for instance in Singapore, and there is a risk that there has already been extensive unobserved transmission of the disease in other regions of the world too. The similarity of the disease caused by 2019-nCoV to other more common respiratory illnesses such as colds and flu, mean that this could well be the case, especially in places that have limited surveillance and testing capacity. If widespread transmission of the virus does begin to occur in other countries, and like I said, this could already be happening, then the most important thing will be to slow the spread of the virus. By doing things like telling people to stay home from work for a couple of weeks if they are sick or have had close contact with a known case (sometime referred to as ‘self-quarantining’) we can limit the number of people sick at a given time. This will hopefully minimise the additional strain put on health systems and limit the number of people unable to work at a given time, avoiding substantial disruption to supply chains and services. The ability to slow the spread of the virus will vary country but country and it is important that we do not neglect low- and middle-income countries, which may not have the resources available to put all the necessary interventions in place and where, with often already struggling health systems, the fallout of such epidemics is often worse.


《华闻周刊》:据我们所知,全球科学家们(例如帝国理工学院和牛津大学的两支研究团队)正在竞相开发用于预防新冠病毒感染的有效疫苗。他们现在处于什么阶段?我们多久才能获得可供广泛使用的有效疫苗?

杰夫科特博士:世界卫生组织总干事谭德塞(Tedros Adhanom Ghebreyesus)最近表示,有效的疫苗或可在18个月内准备就绪。威康信托基金会(Wellcome Trust)董事杰里米·法拉尔(Jeremy Farrar)也称,如果一切顺利,疫苗可能在明年2月面世。但他也明确指出,尽管科学家们共同在努力,但我们至今仍然没有研制出任何一款有效的疫苗来预防可以感染人类的任何冠状病毒(无论是引发SARS的冠状病毒,还是引发普通感冒的冠状病毒)。由于研制疫苗还需要很长的时间,疫苗对于应对当前这波疫情爆发能发挥什么作用,现在很难去讲,但显然它是我们需要重点关注的研究领域和技术。

Tedros Adhanom Ghebreyesus, the Director-General of the World Health Organization, recently suggested that a vaccine might be ready within 18 months. Jeremy Farrar, Director of the Wellcome Trust, suggested one might even be available by February next year, assuming everything goes well. He did also note, however, that despite concerted effort we still don’t have effective vaccines available for any of the other coronaviruses known to infect humans, including the one responsible for SARS or the one responsible for the common cold. With such a long lead time it’s unclear what role a vaccine will play in the response to this outbreak, but it is obviously an important line of enquiry and technology to look into.


《华闻周刊》:除了着眼于未来预防的疫苗,在针对已感染患者的抗病毒药物和治疗方法研究方面,目前有哪些进展?

杰夫科特博士:目前,大量的研究都在关注哪一种医学干预能够有助于改善被感染患者的预后,其中包括靶向治疗的研究。现在,研究界讨论最多的是一种采用“抗逆转录病毒药物”的治疗方法(它通常也被用于治疗HIV艾滋病毒感染者)。这种方法是否真的有效,尚有待观察,但如果可行,它将成为限制该新冠病毒传播并减轻其对个体病例影响的重要工具。

There is a lot of work going on at present looking at what kinds of medical interventions might help improve the outcomes for patients, including the development of targeted treatments. The most widely discussed approach to this at present involves using treatments called antiretrovirals normally used to treat people with HIV. Whether this approach will work is yet to be seen, but if it does it could be an important tool in limiting the spread of the virus and mitigating its impact on individuals. 


本文为《华闻周刊》原创采访,未经授权,请勿转载。


如果您对新型冠状病毒感染疫情也有自己的看法、思考和分析,欢迎投稿至:editor@thechineseweekly.com。

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