是中国数据， WHO report 第8页。 居家（household）感染率3-10%， 密切接触（close contacts）感染率 1-5%。 所有确诊里边78-85%是家庭感染的。
Household transmission In China, human-to-human transmission of the COVID-19 virus is largely occurring infamilies. The Joint Mission received detailed information from the investigation of clustersand some household transmission studies, which are ongoing in a number of Provinces.Among 344 clusters involving 1308 cases (out of a total 1836 cases reported) in GuangdongProvince and Sichuan Province, most clusters (78%-85%) have occurred in families.Household transmission studies are currently underway, but preliminary studies ongoing inGuangdong estimate the secondary attack rate in households ranges from 3-10%.
Contact Tracing China has a policy of meticulous case and contact identification for COVID-19. For example,in Wuhan more than 1800 teams of epidemiologists, with a minimum of 5 people/team, aretracing tens of thousands of contacts a day. Contact follow up is painstaking, with a highpercentage of identified close contacts completing medical observation. Between 1% and5% of contacts were subsequently laboratory confirmed cases of COVID-19, depending onlocation. For example: • As of 17 February, in Shenzhen City, among 2842 identified close contacts, 2842(100%) were traced and 2240 (72%) have completed medical observation. Amongthe close contacts, 88 (2.8%) were found to be infected with COVID-19. • As of 17 February, in Sichuan Province, among 25493 identified close contacts,25347 (99%) were traced and 23178 (91%) have completed medical observation.Among the close contacts, 0.9% were found to be infected with COVID-19. • As of 20 February, in Guangdong Province, among 9939 identified close contacts,9939 (100%) were traced and 7765 (78%) have completed medical observation.Among the close contacts, 479 (4.8%) were found to be infected with COVID-19.
The coronavirus toll linked to a Biogen management meeting in Boston has now jumped to 32 people infected in Massachusetts — with an investment bank in New York City alerting hundreds more about the viral risk. Cambridge-based Biogen confirmed Monday they have warned both Manhattan investment bank Cowen & Co. and Boston’s State Room venue about company managers who have COVID-19 who may have come in contact with others. About 175 Biogen managers coming from all over the world — “Yes, from Italy,” a company spokesman confirmed — gathered for a major meeting of the biotech giant held at the Boston Marriott Long Wharf hotel Feb. 26-27. Italy, at that time, was beginning to see the virus spread. A Biogen “group dinner” was also held the night of Feb. 26 at the State Room on the 33rd floor of 60 State St. overlooking Faneuil Hall. “The restaurant has been notified,” Biogen said. A venue spokeswoman confirmed they catered the event, but declined further comment. A manager from Tennessee and two from Indiana who attended the Biogen meeting have since tested positive for the coronavirus, according to health officials. And another, who went to a Florida conference afterwards, is also reportedly infected. On March 2, a top Biogen manager and assistants then went to the 40th Annual Health Care Conference sponsored by Cowen & Co. held at the Boston Marriott Copley Place. One of those in attendance from Biogen has since “tested positive” for COVID-19, a Cowen spokesman said. The COVID-19 worldwide spread, ironically, was one of the hot topics at the conference. A Cowen & Co. human resources director told the Herald Monday she was aware of the coronavirus risk and a spokesman later said all 300-plus people who attended what was billed as the “event of the year when it comes to healthcare conferences” were notified after the fact about the Biogen link. “We have notified all conference attendees and as of now, there are no cases among Cowen employees nor any other reports from other attendees. We are following CDC guidelines regarding those that may have been in close contact with this individual,” said Dan Gagnier, a Cowen spokesperson. Biogen is one of the world’s largest biotech firms known for its work in Alzheimer’s.
The coronavirus toll linked to a Biogen management meeting in Boston has now jumped to 32 people infected in Massachusetts — with an investment bank in New York City alerting hundreds more about the viral risk.
Cambridge-based Biogen confirmed Monday they have warned both Manhattan investment bank Cowen & Co. and Boston’s State Room venue about company managers who have COVID-19 who may have come in contact with others.
About 175 Biogen managers coming from all over the world — “Yes, from Italy,” a company spokesman confirmed — gathered for a major meeting of the biotech giant held at the Boston Marriott Long Wharf hotel Feb. 26-27. Italy, at that time, was beginning to see the virus spread.
A Biogen “group dinner” was also held the night of Feb. 26 at the State Room on the 33rd floor of 60 State St. overlooking Faneuil Hall. “The restaurant has been notified,” Biogen said. A venue spokeswoman confirmed they catered the event, but declined further comment.
A manager from Tennessee and two from Indiana who attended the Biogen meeting have since tested positive for the coronavirus, according to health officials. And another, who went to a Florida conference afterwards, is also reportedly infected.
On March 2, a top Biogen manager and assistants then went to the 40th Annual Health Care Conference sponsored by Cowen & Co. held at the Boston Marriott Copley Place. One of those in attendance from Biogen has since “tested positive” for COVID-19, a Cowen spokesman said.
The COVID-19 worldwide spread, ironically, was one of the hot topics at the conference.
A Cowen & Co. human resources director told the Herald Monday she was aware of the coronavirus risk and a spokesman later said all 300-plus people who attended what was billed as the “event of the year when it comes to healthcare conferences” were notified after the fact about the Biogen link.
“We have notified all conference attendees and as of now, there are no cases among Cowen employees nor any other reports from other attendees. We are following CDC guidelines regarding those that may have been in close contact with this individual,” said Dan Gagnier, a Cowen spokesperson.
Biogen is one of the world’s largest biotech firms known for its work in Alzheimer’s. this.id. 发表于 3/9/2020 11:16:58 PM
https://www.cdc.gov/mmwr/volumes/69/wr/pdfs/mm6909e1-H.pdf
CDC follow了跟确诊病例接触的家人，路人，医生，还有医生再接触的病人，发现最容易感染的是家人。
当然，这里有个前提是follow的是确诊病人的接触人群，有点偏倚。还有样本例数还不够，可能这10人中正好没有超级传播者。
可能美国这边空气是很干净，悬浮物气溶胶都比较少。想想武汉1月那个雾霾的天气，确实有助于疾病的播散。
有在中美两边实验室做实验的同学说国内做实验时同样的实验全副武装千小心万小心还经常被污染，而在美国这边同样的操作好像也很少有污染。
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补充：
41 楼有mm翻译解读了一下内容，我就引用一下她写的哈
这篇文章是对美国最初发生的“传入性”（Traveled）10例新冠肺炎患者的追踪调查
10个原发输入病人G0，他们感染了多少一代病人了呢（G1）？
经过当地调查，对10个G0病人有接触史的445个病人进行了14天隔离，并追踪这些隔离的病人。
这445个病人分成四组。
A，病人家属组19人（patient’shousehold）：和病人生活居住过；
B，一般社区组104人（communitymembers）：在6英尺以内，和病人接触至少10分钟；
C，医院接触组100人（healthcare setting）：普通人在医疗机构和病人有过接触；
D，医护人员组222人（healthcare personnel）。
在隔离的14天期间，咳嗽、发热等可能和新冠肺炎类似有症状的有54人，经过反复检测，到底有多少被传染上的G1病人呢？
A组：2个； B组：0； C组：0； D组：0。
54个有症状的病人，只有两个是新冠肺炎，而其他的大都是流感！！！！（很正常，流感季节，出现的病人首先应该考虑流感）。日本武汉撤侨数百人的研究也证实了这一点：绝大部分90%有症状（56/63）的病人，都不是新冠肺炎病人。
新发生的2例病人，又有146人接触了这两位新病例，对这146位接触者再次进行了14天的隔离，隔离期间，18人出现了症状，对这18人进行了反复检测，结果，这18人全部为阴性，也就是说，二代病人为零（G2=0）。
在美国最初出现的10例病人，只传了一代2人，且仅仅传给了和病人密切接触的家人。
Re,我现在真的是担心学校，孩子们又一起吃饭
典型的拿着结论找证据。钻石公主号把该做的实验早就已经做过一遍了，可惜CDC要全部再重来一遍。
中国也是的，大部分是家人传染。不然弄方舱干什么。就是发现居家隔离变成居家传染了。
百分之十几的意思～
是不是说，只要防护得力，即使中招以后，大概率还是不会传染给家人的？
小孩没啥症状。全过了一遍可能都没人知道。
SARS的经验是SARS儿童不传染。
我忘了从哪看来的，说是WA最近对在家隔离的病人做的统计。
南京大妈买烤鸭。今年南京吃上亿鸭子的指标完不成了，大家有心理阴影。
其实那个更可能是两个人都摸过同一个地方，接触传染。
太不可思议的事情不是没可能，而是可能有其它原因来源。
这应该是被口水喷的吧
而且他们现在非密切接触都不测，得到的数据都是biased，现在根本不知道被路人传染的概率。
不是病毒不一样，而是有些人更易感。
还有物品啊。老人院接触传播应该是大头。
广东普查过。全省发烧的都查新冠。检查了几十万例。结果99%以上不是。
说明没明确传染途径的没必要浪费精力。
缺点是可能遗漏了没症状的。但或者路过即使染上没症状。
不一样，这个是发烧的人里面有病毒的比例。
现在讨论的是传染了病毒的人里面被家人/同事/路人传染的比例，根据这个判断各种传播途径感染的人比例，然后制定guideline让大家操作。
比如都是家人感染的，那就不要居家隔离了，如果接触传染的很多，那么公司就不要再提供食物之类的。
现在因为很多不给测，所以很多被传染的人都不知道--因为如果我被路人传染了，我不符合条件，不能测，得到的数据是biased，会认为路人不会传染。
中国发现啥了？
如果中国发现最主要的传播途径是这个，那没有必要的全民戴口罩导致医护没有口罩，又怎么解释？
到目前为止，中国如果真的控制住了，也是因为全民隔离措施。和筛查检测这些根本没有关系；因为准确率不靠谱。
中国公布的治疗经验，乱七八糟什么都有。到底哪条是靠谱的？
再说一次，如果中国控制住了，也是因为全民隔离，和其他措施无关。
这个文章真是好消息，跟踪的几百人，包括医护，只有两个家人感染。难道美国这医护瞎带个口罩真的就够了？
这个我同意你，中国的都是经验总结，但经不起推敲，经验太多了。还有一条，中美国情不一样，生活方式空气质量人口密度UV指数都不一样，同样的经验也需要进一步验证，不能照搬。
CDC这个研究还是很有意义的，如果样本量更大一点，观测一下学校，办公场所，公交车这些人群聚集的传播就更好了。
有可能，最近西雅图那些有流感症状的消防队员里面好像也没几例确诊的，测出来都是阴性，不过他们还是isolate准备到14天再出来。
是中国数据， WHO report 第8页。 居家（household）感染率3-10%， 密切接触（close contacts）感染率 1-5%。 所有确诊里边78-85%是家庭感染的。
Household transmission
In China, human-to-human transmission of the COVID-19 virus is largely occurring infamilies. The Joint Mission received detailed information from the investigation of clustersand some household transmission studies, which are ongoing in a number of Provinces.Among 344 clusters involving 1308 cases (out of a total 1836 cases reported) in GuangdongProvince and Sichuan Province, most clusters (78%-85%) have occurred in families.Household transmission studies are currently underway, but preliminary studies ongoing inGuangdong estimate the secondary attack rate in households ranges from 3-10%.
Contact Tracing
China has a policy of meticulous case and contact identification for COVID-19. For example,in Wuhan more than 1800 teams of epidemiologists, with a minimum of 5 people/team, aretracing tens of thousands of contacts a day. Contact follow up is painstaking, with a highpercentage of identified close contacts completing medical observation. Between 1% and5% of contacts were subsequently laboratory confirmed cases of COVID-19, depending onlocation. For example:
• As of 17 February, in Shenzhen City, among 2842 identified close contacts, 2842(100%) were traced and 2240 (72%) have completed medical observation. Amongthe close contacts, 88 (2.8%) were found to be infected with COVID-19.
• As of 17 February, in Sichuan Province, among 25493 identified close contacts,25347 (99%) were traced and 23178 (91%) have completed medical observation.Among the close contacts, 0.9% were found to be infected with COVID-19.
• As of 20 February, in Guangdong Province, among 9939 identified close contacts,9939 (100%) were traced and 7765 (78%) have completed medical observation.Among the close contacts, 479 (4.8%) were found to be infected with COVID-19.
这个report值得一读
https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf
这种新闻看看就算了，如果同一药店呆15s就能被传染，那怎么整个全国就此一例？国内那人口密度，任何一家店和餐馆都至少同时几个人。。
封城了还是可以去超市的，说明超市买菜概率很低，华人戴着口罩去超市没啥必要。
封城后，去超市买菜大部分都戴口罩了。
你这话说的，意大利那个1号，纽约那个律师不都是少数？ 要是各个都跟纽约律师似的，纽约现在数目你敢想么？
德国最初的病例是一位上海女子去德国参加会议感染了好几个人。那个女子总不可能在短短时间内跟那么多人发生亲密关系吧？我觉得这病毒传播有多种渠道和形式，不是家庭传播那么简单。
如果不传染BCD，那中国医护怎么得的？到外省武汉人还那么可怕？那美国伊朗意大利正在发生的传染是哪里来的？
我记得轮子们说过，说这女的跟这公司这几个人都有不可说的亲密，是都有。
我脑洞大开也没想明白这是一个什么公司，开的什么会。。。。
我觉得有几点比较好的经验：居家隔离 戴口罩 建方舱
莫非这些全跟武汉来美国的人有不可告人的关系？
国内早期是否认气溶胶传播的。直到最新的第七版才指出密闭环境下屎尿形成的气溶胶传播的可能性，因为现在已经知道尿和粪便中含有病毒， 而冲马桶很有可能形成气溶胶。 这种事实不讲，是隐瞒，讲了又是极力渲染。
其实， 我有想到雪场因为要造雪是一个比较容易形成气溶胶的地方，所以才会传染的那么厉害。 （这是我个人猜想， 不负责。）
说真的，非常好奇这个group dinner是怎么serve的。研究一下这个会的人都怎么传染的非常重要。
到底是因为握手，拥抱，亲脸，给presentation，还是因为一起group dinner吃buffet了。还有邮轮上，到底是中央空调，还是因为集体用餐。
现在感觉就完全是一团迷雾，完全不知道怎么预防
隔几桌传上，说不定是刚好在带病毒的人后面使用洗手间传上的。
这明显有问题啊。
首先，输入性传染的传播应该有泄漏出来（可能几个接触的人无症状），否则不好解释华盛顿州的那个养老院爆发之后好几个都是跟第一例（亚马逊相亲男）的病毒基因组进化树分析很相近。
其次，美国现在已经进入了社区传播。输入性传播已经不太反应实际情况了。比如最近纽约那个律师，他一个人就感染了3个家人，1个邻居。后来好几十个接触过的都感染了。明显这个研究是为了得到传播只传给亲密接触的家人这个结论，就特意挑选数据（假设是纽约律师那个事情之后的研究结论）。也是为了给CDC只测有密切接触的人的行为找借口，故意忽视已经社区传播的事实。从而通过不测来减少病例数目。感觉CDC在这次疫情控制方面很有问题。
没有气溶胶传染，再说一次！版上也在乱说，专家也乱说。根本没有
是的，难道是希望你回家传染一下下？绵思恐极。。。。
马桶那个是可能的。但只有一瞬间。盖上盖子冲就好了
雪场我感觉更多是湿度温度都适合病毒。。。
完全赞同楼上，国内的研究实在让人感觉东一榔头西一棒，很多研究是政治性的，然后是各种特例消息满天飞，什么病毒潜伏42天了，什么交谈15秒就染病了，不怀疑这些人得病是真，但是真心怀疑这个带上的原因。
看了国内各种文章，反正没看到一篇这样认真分析传染方式的文章。有的是各种野路子的总结，比如楼上所说的武汉80%的人是家庭感染。
就说口罩，前两天我才发现这个事情很搞笑：1. 到现在为止国内没有任何一个研究，来分析口罩对防治新冠到底有没有效果，有多大的效果；2. WHO的指南里面明确说只有不舒服的时候才需要带口罩，说白了是完全否定了国内的的做法。
所以完全赞同楼上，中国的控制实际上是政治强势，不同人所质意的没有技术官僚加入实际上造成了极高的成本。
反观美国，至少能看到各种独立的研究在进行，研究结果在驱动着如何防疫。
一般环境要满足气溶胶传染的条件，几乎不可能，所以只会考虑发生在医院插管的手术室。
粪口传染，当然是接触传染了，不提主要的接触传染，却纠结于不确定有没有的气溶胶？
滑雪的生活区，小，挤，不讲究，人杂，接触传染妥妥的。ps, 滑雪场不好洗手。
这主要是接触传染是哪里看来的？
我看的英语资料说是droplets，飞沫传染吧。
接触传染，就是摸到病毒后，又摸自己，被传染。粪口传染也是一种接触传染。
droplets落在物体表面，你摸了，再摸自己的脸鼻口，中了，接触传染。droplets喷啊喷，你没戴口罩，被喷，吸入，中了，飞沫传染。这是我的理解。
同意你的结论，但论据有瑕疵，我手贱修正一下。实事求是地说不能完全否定国内的研究，但是靠谱的研究还是太少了， 硕果仅存的也往往被乱七八糟的媒体报道和牛鬼蛇神专家淹没了。
“楼上所说的武汉80%的人是家庭感染” 不是野路子总结，是WHO-China joint report第八页。（https://www.who.int/docs/default-source/coronaviruse/who-china-joint-mission-on-covid-19-final-report.pdf） 这个报告也分析了传染方式， 居家3-10%， 密切接触1-5%，以及医疗和监狱特殊setting。
口罩是否有效这个，是有SARS的研究based，同样是droplets传播用在Covid-19上应该不算错。https://mp.weixin.qq.com/s/46pgeoqjUeCkdNC120FE8A 这是清华一个报告改成的科普， 里面有reference实验和文章，讨论droplets传播安全距离，口罩有效性等。key points是，正常呼吸安全距离1米，喷嚏/咳嗽安全距离>10米。哪怕普通呼吸，1米这个距离对于国内公共场所的人口密度来说太难了，这点跟很多其他国家都是不同的。
不管中美独立踏实的研究都应该支持，哪怕是看上去重复性的，不同环境影响结论。 好比武汉80%是居家传播这个，完全lockdown条件下显然会是居家传播dominant，美国的情况很可能比例不同。 但是这个实验样本还是太小，很可能还有bias。
对于中国国情，尤其中国公共厕所的条件，大量蹲坑的存在的现实， 哪里来的盖子，危险悉数不是说没有就没有。
至于美国，公共厕所有盖子的也不多见吧。 不过美国厕所条件好太多了。
列举可能的传染渠道是必须的吧。
说明意大利人外遇多？
国内新闻都是弱智。有问题吗？
中国绝大多数家庭，家里一个人发现的时候，家人都感染过了。