關于COVID-19的無聲傳播者，我們知道些什么

關于COVID-19的無聲傳播者，我們知道些什么

Is it possible to be infected with the coronavirus and show no symptoms? Or go through a period of several days before symptoms kick in?

有可能感染了冠狀病毒而沒有癥狀嗎?或者經(jīng)歷一段時間才出現(xiàn)癥狀?

And even in this stage with no cough, no fever, no sign of illness, could you be transmitting the virus to others?

即使在不咳嗽，不發(fā)燒，沒有生病跡象的這個階段，你能把病毒傳染給別人嗎?

"There is evidence that SARS-CoV-2 has this ability to spread silently," says Shweta Bansal, an infectious disease modeler at Georgetown University.

“有證據(jù)表明SARS-CoV-2具有無聲傳播的能力，”喬治城大學的傳染病模型師施維塔·班賽爾說。

Indeed, cases of COVID-19 among nursing home residents, choir groups and familiesfuel a growing concern about people who are infected, yet feel generally OK and go about their daily lives, giving the virus to friends, family members and strangers without knowing that they themselves have it.

的確，療養(yǎng)院居民、唱詩班團體和家庭中出現(xiàn)的COVID-19病例，加劇了人們對感染者的擔憂，這些人雖然總體感覺良好，但仍在日常生活中活動，將病毒傳染給朋友、家人和陌生人，卻不知道自己也感染了病毒。

But there are wide gaps in our understanding of how many people fit this category of "silent spreaders" — as they're called by some public health researchers — and how much they contribute to transmission of the disease.

但是，我們對有多少人屬于這類“無聲傳播者”(一些公共衛(wèi)生研究人員將其稱為“無聲傳播者”)以及他們對疾病傳播的貢獻有多大的認識還存在很大的差距。

Silent spreaders can be divided into three categories: asymptomatic, presymptomatic and very mildly symptomatic. Here's what we know about these variations.

無聲傳播者可分為三類：無癥狀，癥狀前階段和非常輕微的癥狀。以下是我們對這些變化的了解。

Asymptomatic: people who carry the active virus in their body but never develop any symptoms

無癥狀者:體內(nèi)攜帶有活性病毒但從未出現(xiàn)任何癥狀的人

"Nothing at all," says Tara C. Smith, an epidemiologist at Kent State University's College of Public Health. "No fever, no gastrointestinal issues, no breathing issues, no coughing, none of that."

肯特州立大學公共衛(wèi)生學院的流行病學家塔拉·C·史密斯說：“什么都沒有發(fā)生。”不發(fā)燒，沒有胃腸道問題，沒有呼吸問題，不咳嗽，都沒有。”

As you might imagine, it's hard to figure out when someone has a disease but shows no signs of it.

正如你所想象的，很難判斷一個人什么時候得了病，但卻沒有任何癥狀。

Some cases of asymptomatic carriers have been confirmed by finding and testing people who were in close contact with COVID-19 patients. For those who tested positive without symptoms, follow-up exams confirmed that about 25% continued to show no signs, World Health Organization officials said on April 1. citing data from China.

通過發(fā)現(xiàn)和檢測與COVID-19患者密切接觸的人，已確認了一些無癥狀攜帶者病例。世界衛(wèi)生組織官員4月1日援引中國的數(shù)據(jù)說，對那些檢測呈陽性但沒有癥狀的人，后續(xù)檢查證實約有25%的人仍然沒有任何癥狀。

No one can truly determine the impact of asymptomatic cases on spread until there's more testing. But so far, they have made up a sliver of the total number of people who've tested positive. And the affected individuals seem to skew young.

在進行更多的檢測之前，沒有人能夠真正確定無癥狀病例對傳播的影響。但到目前為止，他們只占檢測呈陽性的總人數(shù)的一小部分。受影響的個體似乎傾向于年輕人。

A small clinical study from Nanjing, China, followed 24 people who tested positive but didn't show overt symptoms at the time. In the one to three weeks after diagnosis, seven continued showing no symptoms. Their median age was 14.

來自中國南京的一項小型臨床研究跟蹤了24名測試呈陽性但當時沒有表現(xiàn)出明顯癥狀的人。在確診后的一至三周內(nèi)，有七名患者沒有出現(xiàn)任何癥狀。他們的平均年齡是14歲。

"Can those people who are completely asymptomatic, who never develop any symptoms, transmit the infection? That's still kind of an open question," says Smith.

“那些完全沒有癥狀，從來沒有出現(xiàn)任何癥狀的人會傳播感染嗎?”這仍然是一個懸而未決的問題，”史密斯說。

Presymptomatic: people who have been infected and are incubating the virus but don't yet show symptoms

癥狀前階段:已被感染，病毒正在潛伏，但尚未出現(xiàn)癥狀的人

After infection, symptoms might not develop for five to six days — or even two weeks, according to the Annals of Internal Medicine. The time between catching the virus and showing symptoms is called the presymptomatic phase.

根據(jù)《內(nèi)科學年鑒》，感染之后，癥狀可能在5 - 6天內(nèi)不會出現(xiàn)，甚至2周內(nèi)也不會出現(xiàn)。從感染病毒到出現(xiàn)癥狀之間的時間稱為癥狀前階段。

How do these individuals figure into transmission?

這些人是如何感染的?

People appear to be most infectious right around the time when symptoms start, said Maria Van Kerkhove, technical lead for the WHO's Health Emergencies Programme, at an April 1 news conference. However, "we do have evidence, from testing and modeling studies, that suggest people who are presymptomatic can definitely transmit this virus," says Smith, the epidemiologist, most likely in the one to three days before they start showing symptoms, according to the WHO.

在4月1日的一次新聞發(fā)布會上，世衛(wèi)組織衛(wèi)生應急方案技術負責人瑪麗亞·范克霍夫說，在癥狀開始的時候，人們似乎最具傳染性。然而，據(jù)世衛(wèi)組織稱，“我們確實有證據(jù)，從測試和模型研究來看，表明癥狀前的人肯定可以傳播這種病毒，”流行病學家史密斯說，最有可能是在癥狀出現(xiàn)前的一到三天。

So far, presymptomatic is a much more common category than asymptomatic. About 75% of people who test positive without showing symptoms turn out to be presymptomatic, displaying coughing, fatigue, fever and other signs of COVID-19 in a later follow-up exam, said Van Kerkhove.

到目前為止，癥狀前階段比無癥狀更常見的。范克霍夫說，大約75%的人在沒有表現(xiàn)出癥狀的情況下檢測呈陽性，被證明是是癥狀前階段，在隨后的隨訪檢查中表現(xiàn)出咳嗽、疲勞、發(fā)燒和其他COVID-19的癥狀。

Very mildly symptomatic: people who feel a little unwell from a COVID-19 infection but continue to come in close contact with others

非常輕微的癥狀：由于COVID-19感染而感到有點不適，但仍與他人密切接觸的人

"We're very lucky that this isn't a severe infection for everyone, but because of that, some people feel a little sick and power through," says Seema Lakdawala, a flu researcher at the University of Pittsburgh.

匹茲堡大學流感研究人員西瑪·拉克達瓦拉說：“我們非常幸運，這并不是對每個人來說都是嚴重的感染，但正因為如此，一些人感到有點不舒服，但還是挺過來了。”。

Spreading COVID-19 while having a cough or very mild fever doesn't fully count as silent transmission, says Bansal, the infectious disease modeler: "There's some signal there at least."

傳染病建模師班賽爾說，在咳嗽或非常輕微的發(fā)燒時傳播COVID-19并不完全算是無聲傳播：“至少有一些信號。”

But people who continue to frequent communal and public places with a light cough or mild fever may unwittingly spread the disease in the early days of symptom onset — the time they're thought to be most infectious.

但是，那些經(jīng)常在公共場所出現(xiàn)輕微咳嗽或輕微發(fā)燒的人，可能在癥狀出現(xiàn)的早期就不知不覺地傳播了這種疾病，這段時間被認為是最具傳染性的。