What the cruise-ship outbreaks reveal about COVID-19

喀秋莎 2020-3-27 5307

When COVID-19 was detected among passengers on the cruise ship Diamond Princess, the vessel offered a rare opportunity to understand features of the new coronavirus that are hard to investigate in the wider population. Some of the first studies from the ship — where some 700 people were infected — have revealed how easily the virus spreads, provided estimates of the disease’s severity and allowed researchers to investigate the share of infections with no symptoms.


Information gleaned from such outbreaks is crucial for people making decisions on how to manage the epidemic, say researchers.


“Cruise ships are like an ideal experiment of a closed population. You know exactly who is there and at risk and you can measure everyone,” says John Ioannidis, an epidemiologist at Stanford University in California. This is very different from trying to study the spread in a wider population, where only some people, typically those with severe symptoms, are tested and monitored.


Diamond Princess

On 1 February, a passenger who had disembarked from the Diamond Princess days earlier in Hong Kong tested positive for the COVID-19 coronavirus. The ship was quarantined immediately after it arrived in Japanese waters on 3 February, with 3,711 passengers and crew members on board. Over the next month, more than 700 people on board were infected — including a nurse — and for weeks the ship was the site of the largest outbreak outside China.


Outbreaks seed easily on the vessels because of the close confines and high proportions of older people who tend to be more vulnerable to the disease. Since the Diamond Princess, at least 25 other cruise ships have confirmed COVID-19 cases — including 78 cases on the Grand Princess, which was quarantined off the coast of California. Returned passengers have also seeded outbreaks in countries including the United States.



Covert coronavirus infections could be seeding new outbreaks

Japanese officials performed more than 3,000 tests on the Diamond Princess, starting with older passengers and those with symptoms. Some passengers were tested more than once, offering insight into the virus’s spread over time. Testing almost all of the passengers and crew helped researchers to understand a key blind spot in many infectious-disease outbreaks — how many people are actually infected, including those who have mild symptoms or none at all. These cases often go undetected in the general population.


Using the Diamond Princess data, a team reports in Eurosurveillance1 that by 20 February, 18% of all infected people on the ship had no symptoms. “That is a substantial number,” says co-author Gerardo Chowell, a mathematical epidemiologist at Georgia State University in Atlanta. But the passengers included a large number of elderly people, who are most likely to develop severe disease if infected, so the share of asymptomatic people in the general population is likely to be higher, he says.


Disease severity

Another team used data from the ship to estimate2 that the proportion of deaths among confirmed cases in China, the case fatality rate (CFR), was around 1.1% — much lower than the 3.8% estimated by the World Health Organization (WHO).


The WHO simply divided China’s total number of deaths by the total number of confirmed infections, says Timothy Russell, a mathematical epidemiologist at the London School of Hygiene and Tropical Medicine. That method does not take into account that only a fraction of infected people are actually tested, and so it makes the disease seem more deadly than it is, he says.


By contrast, Russell and his colleagues used data from the ship — where almost everyone was tested, and all seven deaths recorded — and combined it with more than 72,000 confirmed cases in China, making their CFR estimate more robust. The results have been posted on the biomedical preprint server medRxiv, and have not been peer-reviewed yet.


The group also estimates that the infection fatality rate (IFR) in China — the proportion of all infections, including asymptomatic ones, that result in death — is even lower, at roughly 0.5%. The IFR is especially tricky to calculate in the population, because some deaths go undetected if the person didn’t show symptoms or get tested.



The coronavirus pandemic in five powerful charts

The IFR is an important indicator to help public-health officials understand disease severity and how to intervene, says Marc Lipsitch, an infectious-disease epidemiologist at the Harvard T.H. Chan School of Public Health in Boston, Massachusetts. “This is an important effort, but one important caveat is that the infections were ascertained by viral testing” and might have missed people who had been infected but recovered, he says.


Ioannidis adds that the studies using Diamond Princess data could benefit from the addition of the medical histories of those on board, such as whether or not people smoked. “We know that not only age, but also presence of medical diseases such as chronic obstructive pulmonary disease, heart disease, diabetes and other conditions increase the risk of a bad outcome,” he says.


Cabin quarantine

Chowell also looked at how effective the stringent containment measures introduced on the Diamond Princess were in reducing the virus’s spread. From 5 February, passengers on the ship were confined to their cabins for two weeks or more.


He and Kenji Mizumoto, an epidemiologist at Kyoto University in Japan, report in Infectious Disease Modelling3 that the day the quarantine was introduced, one person could go on to infect more than 7 others. The infection rate was probably quite high because people were living in close quarters and touching surfaces contaminated with the virus, says Chowell.



What China’s coronavirus response can teach the rest of the world

But after people were confined to their rooms, the average number of others to whom one infected person passed the virus dropped below one. This suggests that the quarantine averted a lot of infections, says Chowell. However, it wasn’t perfect: passengers could still infect their room-mates and crew members, he says.


Although insights from the ship about the virus’s spread and severity are valuable, it is difficult to draw lessons from its quarantine for those countries implementing similar lockdown measures, says Ioannidis. “A whole country is not a ship.”


doi: 10.1038/d41586-020-00885-w


我在上班,别发骚图了。
最新回复 (9)
  • 正统罗马 2020-3-27
    0 2
    看不懂(直球)
    你的恶名从爱尔兰到契丹无人不知无人不晓
  • 古墨 2020-3-27
    0 3
     undefined
    在苍穹的尽头
  • poppoppoppp 2020-3-27
    4 4
    翻译<br><br>当在“钻石公主”号游轮的乘客中检测到COVID-19时,该船提供了难得的机会来了解新的冠状病毒的特征,这些特征很难在更广泛的人群中进行研究。该船的第一批研究(有700人被感染)揭示了病毒的扩散程度,提供了疾病严重程度的估计值,并允许研究人员调查无症状感染的比例。<br><br><br><br>研究人员说,从此类暴发中收集的信息对于人们决定如何管理该流行病至关重要。<br><br><br><br>游轮就像封闭人群的理想实验。您确切地知道谁在那儿并且处于危险之中,并且您可以对每个人进行测量。”加州斯坦福大学的流行病学家John&nbsp;Ioannidis说。这与尝试研究更广泛的人群中的传播情况大不相同,在更广泛的人群中,仅对部分人(通常是症状严重的人)进行测试和监视。<br><br><br><br>钻石公主<br><br>2月1日,几天前在香港从钻石公主号登机的一名乘客的COVID-19冠状病毒检测结果呈阳性。该船于2月3日抵达日本海域后立即被隔离,船上有3,711名乘客和船员。在接下来的一个月中,船上有700多人被感染-包括一名护士-数周以来,这艘船是中国以外最大规模的疫情爆发地点。<br><br><br><br>由于密闭的地区和比例较高的老年人更容易感染这种疾病,因此很容易在船上爆发种子。自钻石公主号以来,至少有25艘游轮确认了COVID-19案-包括在加州海岸隔离的大公主号上的78例。返程旅客在美国等国家也爆发了疫情。<br><br><br><br><br><br>秘密冠状病毒感染可能会引发新的爆发<br><br>日本官员对“钻石公主”号进行了3000多次测试,从年龄较大的乘客和有症状的乘客开始。一些乘客接受了不止一次的测试,从而了解了病毒在一段时间内的传播情况。对几乎所有乘客和机组人员进行的测试有助于研究人员了解许多传染病暴发的关键盲点-实际感染了多少人,包括那些症状较轻或根本没有症状的人。这些病例在普通人群中通常未被发现。<br><br><br><br>使用“钻石公主”数据,一个团队在Eurosurveillance1中报告,到2月20日,船上所有感染者中有18%没有症状。&nbsp;“这是一个很大的数字,”合著者,亚特兰大乔治亚州立大学数学流行病学家Gerardo&nbsp;Chowell说。他说,但是乘客中包括大量的老年人,他们很可能在感染后会患上严重疾病,因此无症状人群在普通人群中所占的比例可能更高。<br><br><br><br>疾病严重程度<br><br>另一个小组使用船上的数据估算2,中国确诊病例中的死亡比例(病死率)约为1.1%,远低于世界卫生组织(WHO)估计的3.8%。<br><br><br><br>伦敦卫生与热带医学学院的数学流行病学家蒂莫西·拉塞尔说,世界卫生组织只是将中国的死亡总数除以确诊的感染总数。他说,这种方法没有考虑到只有一小部分感染者得到了实际检测,因此使这种疾病看起来比实际更致命。<br><br><br><br>相比之下,拉塞尔和他的同事使用了该船的数据(几乎每个人都进行了测试,并记录了全部7例死亡),并将其与中国72,000多例确诊病例相结合,使他们的病死率估算更加可靠。结果已发布在生物医学预印本服务器medRxiv上,尚未经过同行评审。<br><br><br><br>该小组还估计,中国的感染死亡率(IFR)(包括无症状的导致死亡的所有感染的比例)甚至更低,约为0.5%。在人口中计算IFR尤其棘手,因为如果该人没有表现出症状或未接受检查,则某些死亡不会被发现。<br><br><br><br><br><br>五个强大图表中的冠状病毒大流行<br><br>哈佛大学传染病流行病学专家马克·里普西奇(Marc&nbsp;Lipsitch)表示,IFR是帮助公共卫生官员了解疾病严重程度以及如何进行干预的重要指标。位于马萨诸塞州波士顿的Chan公共卫生学院。他说:“这是一项重要的努力,但重要的警告是,感染是通过病毒检测确定的”,并且可能错过了被感染但康复的人。<br><br><br><br>约阿尼迪斯补充说,使用钻石公主数据进行的研究可能会受益于船上人员病史的增加,例如人们是否吸烟。&nbsp;
    空白不败,千秋万代
  • poppoppoppp 2020-3-27
    0 5
    求赞
    空白不败,千秋万代
  • 0 6
    要做个听神明大人话的好孩子哦
  • 凌霄花 2020-3-27
    0 7
    好,好活! undefined
    给汉化和曾经上香~
  • 云淡风清 2020-3-27
    0 8
    要是像联盟那样,在每段中间插入译文就好了
    这个人很懒,什么也没有留下!
  • 革子令 2020-3-27
    0 9
    我好喜欢病娇
  • 老翔驾到 2020-3-28
    0 10
    其实可以自行安装一个网页翻译软件的说
    考上网络大学,中出电子优香
    • ACG里世界
      11
          
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