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Outbreak of new coronavirus pneumonia
At the turning point of the Wuhan epidemic: Will asymptomatic new crown virus infected people break through the prevention and control system?
First Financial 2020-01-31 10:14:20
Zhang Wenhong
How does asymptomatic infection affect the development of the epidemic?
Recently, the outbreak of new coronavirus pneumonia in Wuhan has attracted worldwide attention, and the bombardment of information on social media has affected the hearts of people across the country. In order to help everyone understand the dynamic changes of the epidemic, the WeChat public account “Huashan Infection” of Huashan Hospital's Infection Department affiliated to Fudan University updates the relevant data of the epidemic every day, and invites Professor Zhang Wenhong, director of the Department of Infectious Diseases of Huashan Hospital, on the trend, hot issues and related issues Cautions, specifically for Q & A interpretation.
Professor Zhang Wenhong is also the leader of the Shanghai New Coronavirus Pneumonia Medical Treatment Expert Group.
Daily battle report: Asymptomatic infections sneak into our prevention and control system?
...
National Health Commission: Among the close contacts of sporadic cases, we have observed that there may be asymptomatic infections. Although there are no symptoms, the nucleic acid test is positive.
Other patients have such symptoms, such as fever not being obvious, occasional dry cough or fatigue. Such patients, from the perspective of the law of infectious diseases, also have a certain spreading power, which brings certain difficulties and complexity to our prevention and control work. As the current technology for screening for infectious agents is mainly symptomatic, or even only for patients with pneumonia, asymptomatic patients may be missed, and then spread in a wide range in communities and shopping malls, and the second generation appears. Three generations and even N generations.
Reports of asymptomatic infection are gradually appearing everywhere, causing public concern. Asymptomatic means that these infected people lack the fever and respiratory symptoms of typical new coronavirus infection, but the nucleic acid test is positive. It is feared that the emergence of asymptomatic infection will make the epidemic more difficult to control because there may be more cases of infection after contact with any symptomatic person, which also makes some of our previous prevention and control screening standards meaningless. So what are the effects of asymptomatic infections on the development of the epidemic?
We answer from the following aspects!
Does the so-called neocrown virus asymptomatic infection actually exist?
First of all, it is entirely possible that such so-called asymptomatic infections may occur. Based on the analysis of current clinical data, compared with SARS and MERS, the proportion of mild patients is higher, and mild and asymptomatic patients often have there is no absolute dividing line . So asymptomatic can also be very mild, making it difficult for patients to detect. From the current epidemiological data, at least from the perspective of family clustered cases, the source cases have preceded the onset. The so-called source cases (also known as academically indicated cases) infect people when they are asymptomatic. This is not called asymptomatic infection. At present, those who are more asymptomatic are the Henan Anyang family who recently reported on the Internet. The so-called indicated cases have been asymptomatic. In fact, this situation is not good enough to say that it must be an asymptomatic case. It is also possible that the case had very mild symptoms without knowing it, and soon entered the recovery period. Whether it is asymptomatic requires a series of virological and serological studies in people who do not develop disease in close contacts to draw conclusions.
A classic case in history tells you what an asymptomatic person is
Is it possible that an asymptomatic person is a persistent asymptomatic person ? With the addition of two words, the epidemiological significance is completely different. Persistent infection indicates that the infected person is always a source of infection, and he can constantly cause contact infection. A persistent asymptomatic infection called "typhoid Mary" appeared in New York, USA in the early last century. This family cook, named Mary, was infected with typhoid bacteria (a type of bacteria that causes typhoid fever) but did not have symptoms of typhoid, and accidentally infected 51 people, three of whom died. She was forcibly quarantined twice by New York public health authorities for a total of 30 years. So is there a similar situation for the new coronavirus in 2019? We have to say that this is almost impossible . Although the data on the longest time of nucleic acid positivity in known patients is not known at present, from previous respiratory viruses such as influenza, parainfluenza, rhinovirus, metapneumovirus, and adenovirus to the six coronaviruses previously discovered none of them had experienced persistent asymptomatic infections .
Can asymptomatic cases become super-spreaders and lead to an out-of-control situation?
Everyone is more worried about whether there is no symptoms, but they are a super communicator. The so-called super communicator , when we were SARS, we called the drug king, that is, a patient infected multiple patients at the same time due to various reasons. In the news, we called these people "big V". Why is it less likely? Coronavirus, as a virus that is mainly transmitted through the respiratory tract, spreads the virus to surrounding susceptible people by means of droplets produced by patients such as coughing and sneezing. And if a person is not infected with respiratory symptoms, it is difficult to produce an effective route of transmission . In an inappropriate analogy, you can hardly ask a network "big V" to remain unknown, but at the same time be able to broadcast information to a large number of people at the same time. Secondly, from the experience of previous SARS, the poison king at that time was mostly transmitted to many close contacts due to severe cases with very obvious respiratory symptoms (such as close family care of patients, medical staff, or lack of the risk of isolation in emergency settings such as emergency rooms to other patients in close proximity), or due to medical staff's ineffective protection of themselves during medical procedures that produce aerosols such as intubation, and the risk of asymptomatic infection It almost doesn't exist, so don't worry too much.
Proportion of asymptomatic infection requires retrospective serological study
So how many people in the crowd are asymptomatic? For the 2019 new coronavirus, further research is needed. In general, to know how many people in a population have been infected with an infectious disease, it is more meaningful to detect antibodies than nucleic acids. Because we mentioned earlier that nucleic acids will only appear in the body for a period of time. As the virus is immune cleared by the body, nucleic acids will not be detected. The absence of a nucleic acid indicates that it is not contagious . However, specific antibodies are produced in the body (this process usually takes 1-4 weeks) and persists. In this way, when we want to know how many people in the population have ever been infected with a virus, the most effective method is to detect the proportion of people who have developed antibodies in the blood . This value can be used to estimate how many people have been infected. This number is then subtracted from the number of clearly infected people (including the sum of recovered and dead people), and the rest is the proportion of asymptomatic people. At present, new cases are constantly appearing across the country, so the proportion of asymptomatic infections cannot be calculated well , but if it is possible to detect the first-generation cases later (for example, the entire South China in 2019 The seafood market has people who have been exposed to antibodies), and it may be possible to understand the proportion of asymptomatic infections.
Min public as long as the firm implementation of the current control measures sufficient to prevent and control the threat of asymptomatic infected persons
The previous questions are clear, and how to prevent and control asymptomatic infection becomes clearer. First of all, we still repeatedly emphasize good personal hygiene , proper hand washing (soap and running water) and correct cough (using paper towels or elbows). Second, during high epidemics, avoid going to crowded places and minimize the chance of close contact with strangers. If it is absolutely necessary, you should wear a mask . Finally, during the high epidemic period, for patients who cannot completely rule out infection with the new coronavirus without fever and respiratory symptoms, but who have been treated for other reasons (especially with an epidemiological history), avoid unnecessary aerosols as much as possible for operations such as sputum suction and intubation, if you have to do so, you should find a way to conduct nucleic acid screening or protect medical personnel according to the third level protection.
For those with asymptomatic infections, to sum up, there is the possibility of "asymptomatic infections", but their chances of becoming a continuous source of infection and super spreaders are very small, and the proportion of asymptomatic infections needs further research. Existing Hygiene habits and sound medical procedures can help to prevent infection by these asymptomatic people.
Professor Lu Shan, Executive Editor of Emerging Mirobes and Infections, Massachusetts International Medical College, is a friend of the author. He is a Chinese American and a more objective scientist. His latest opinion is to lock himself in this way. , Inactivity has a huge effect on virus control, and the subsequent epidemic situation is likely to change, or even disappear completely over a period of time, is possible.
In short, the key to current prevention and control is to resolutely implement the two-week control and resolutely shut down potential asymptomatic carriers. According to Professor Lu Shan's opinion, this is already the case. We might as well be more optimistic. Now the people of the whole country do not go out at home. They do not go to work during the Spring Festival. They are also delayed to work. Compared with the infection during normal work, Very lucky.
Wen / Wang Xinyu (Deputy Chief Physician, Department of Infectious Diseases, Huashan Hospital) Zhang Wenhong (Leader of Shanghai Medical Treatment Experts Group, Director of Infectious Diseases Department of Huashan Hospital)
(This article is reproduced from the "Huashan Infection" public account after authorization, and the copyright belongs to the Department of Infectious Diseases, Huashan Hospital, Fudan University.)
Editor-in-chief: Yunhui Yun
Outbreak of new coronavirus pneumonia
At the turning point of the Wuhan epidemic: Will asymptomatic new crown virus infected people break through the prevention and control system?
First Financial 2020-01-31 10:14:20
Zhang Wenhong
How does asymptomatic infection affect the development of the epidemic?
Recently, the outbreak of new coronavirus pneumonia in Wuhan has attracted worldwide attention, and the bombardment of information on social media has affected the hearts of people across the country. In order to help everyone understand the dynamic changes of the epidemic, the WeChat public account “Huashan Infection” of Huashan Hospital's Infection Department affiliated to Fudan University updates the relevant data of the epidemic every day, and invites Professor Zhang Wenhong, director of the Department of Infectious Diseases of Huashan Hospital, on the trend, hot issues and related issues Cautions, specifically for Q & A interpretation.
Professor Zhang Wenhong is also the leader of the Shanghai New Coronavirus Pneumonia Medical Treatment Expert Group.
Daily battle report: Asymptomatic infections sneak into our prevention and control system?
...
National Health Commission: Among the close contacts of sporadic cases, we have observed that there may be asymptomatic infections. Although there are no symptoms, the nucleic acid test is positive.
Other patients have such symptoms, such as fever not being obvious, occasional dry cough or fatigue. Such patients, from the perspective of the law of infectious diseases, also have a certain spreading power, which brings certain difficulties and complexity to our prevention and control work. As the current technology for screening for infectious agents is mainly symptomatic, or even only for patients with pneumonia, asymptomatic patients may be missed, and then spread in a wide range in communities and shopping malls, and the second generation appears. Three generations and even N generations.
Reports of asymptomatic infection are gradually appearing everywhere, causing public concern. Asymptomatic means that these infected people lack the fever and respiratory symptoms of typical new coronavirus infection, but the nucleic acid test is positive. It is feared that the emergence of asymptomatic infection will make the epidemic more difficult to control because there may be more cases of infection after contact with any symptomatic person, which also makes some of our previous prevention and control screening standards meaningless. So what are the effects of asymptomatic infections on the development of the epidemic?
We answer from the following aspects!
Does the so-called neocrown virus asymptomatic infection actually exist?
First of all, it is entirely possible that such so-called asymptomatic infections may occur. Based on the analysis of current clinical data, compared with SARS and MERS, the proportion of mild patients is higher, and mild and asymptomatic patients often have there is no absolute dividing line . So asymptomatic can also be very mild, making it difficult for patients to detect. From the current epidemiological data, at least from the perspective of family clustered cases, the source cases have preceded the onset. The so-called source cases (also known as academically indicated cases) infect people when they are asymptomatic. This is not called asymptomatic infection. At present, those who are more asymptomatic are the Henan Anyang family who recently reported on the Internet. The so-called indicated cases have been asymptomatic. In fact, this situation is not good enough to say that it must be an asymptomatic case. It is also possible that the case had very mild symptoms without knowing it, and soon entered the recovery period. Whether it is asymptomatic requires a series of virological and serological studies in people who do not develop disease in close contacts to draw conclusions.
A classic case in history tells you what an asymptomatic person is
Is it possible that an asymptomatic person is a persistent asymptomatic person ? With the addition of two words, the epidemiological significance is completely different. Persistent infection indicates that the infected person is always a source of infection, and he can constantly cause contact infection. A persistent asymptomatic infection called "typhoid Mary" appeared in New York, USA in the early last century. This family cook, named Mary, was infected with typhoid bacteria (a type of bacteria that causes typhoid fever) but did not have symptoms of typhoid, and accidentally infected 51 people, three of whom died. She was forcibly quarantined twice by New York public health authorities for a total of 30 years. So is there a similar situation for the new coronavirus in 2019? We have to say that this is almost impossible . Although the data on the longest time of nucleic acid positivity in known patients is not known at present, from previous respiratory viruses such as influenza, parainfluenza, rhinovirus, metapneumovirus, and adenovirus to the six coronaviruses previously discovered none of them had experienced persistent asymptomatic infections .
Can asymptomatic cases become super-spreaders and lead to an out-of-control situation?
Everyone is more worried about whether there is no symptoms, but they are a super communicator. The so-called super communicator , when we were SARS, we called the drug king, that is, a patient infected multiple patients at the same time due to various reasons. In the news, we called these people "big V". Why is it less likely? Coronavirus, as a virus that is mainly transmitted through the respiratory tract, spreads the virus to surrounding susceptible people by means of droplets produced by patients such as coughing and sneezing. And if a person is not infected with respiratory symptoms, it is difficult to produce an effective route of transmission . In an inappropriate analogy, you can hardly ask a network "big V" to remain unknown, but at the same time be able to broadcast information to a large number of people at the same time. Secondly, from the experience of previous SARS, the poison king at that time was mostly transmitted to many close contacts due to severe cases with very obvious respiratory symptoms (such as close family care of patients, medical staff, or lack of the risk of isolation in emergency settings such as emergency rooms to other patients in close proximity), or due to medical staff's ineffective protection of themselves during medical procedures that produce aerosols such as intubation, and the risk of asymptomatic infection It almost doesn't exist, so don't worry too much.
Proportion of asymptomatic infection requires retrospective serological study
So how many people in the crowd are asymptomatic? For the 2019 new coronavirus, further research is needed. In general, to know how many people in a population have been infected with an infectious disease, it is more meaningful to detect antibodies than nucleic acids. Because we mentioned earlier that nucleic acids will only appear in the body for a period of time. As the virus is immune cleared by the body, nucleic acids will not be detected. The absence of a nucleic acid indicates that it is not contagious . However, specific antibodies are produced in the body (this process usually takes 1-4 weeks) and persists. In this way, when we want to know how many people in the population have ever been infected with a virus, the most effective method is to detect the proportion of people who have developed antibodies in the blood . This value can be used to estimate how many people have been infected. This number is then subtracted from the number of clearly infected people (including the sum of recovered and dead people), and the rest is the proportion of asymptomatic people. At present, new cases are constantly appearing across the country, so the proportion of asymptomatic infections cannot be calculated well , but if it is possible to detect the first-generation cases later (for example, the entire South China in 2019 The seafood market has people who have been exposed to antibodies), and it may be possible to understand the proportion of asymptomatic infections.
Min public as long as the firm implementation of the current control measures sufficient to prevent and control the threat of asymptomatic infected persons
The previous questions are clear, and how to prevent and control asymptomatic infection becomes clearer. First of all, we still repeatedly emphasize good personal hygiene , proper hand washing (soap and running water) and correct cough (using paper towels or elbows). Second, during high epidemics, avoid going to crowded places and minimize the chance of close contact with strangers. If it is absolutely necessary, you should wear a mask . Finally, during the high epidemic period, for patients who cannot completely rule out infection with the new coronavirus without fever and respiratory symptoms, but who have been treated for other reasons (especially with an epidemiological history), avoid unnecessary aerosols as much as possible for operations such as sputum suction and intubation, if you have to do so, you should find a way to conduct nucleic acid screening or protect medical personnel according to the third level protection.
For those with asymptomatic infections, to sum up, there is the possibility of "asymptomatic infections", but their chances of becoming a continuous source of infection and super spreaders are very small, and the proportion of asymptomatic infections needs further research. Existing Hygiene habits and sound medical procedures can help to prevent infection by these asymptomatic people.
Professor Lu Shan, Executive Editor of Emerging Mirobes and Infections, Massachusetts International Medical College, is a friend of the author. He is a Chinese American and a more objective scientist. His latest opinion is to lock himself in this way. , Inactivity has a huge effect on virus control, and the subsequent epidemic situation is likely to change, or even disappear completely over a period of time, is possible.
In short, the key to current prevention and control is to resolutely implement the two-week control and resolutely shut down potential asymptomatic carriers. According to Professor Lu Shan's opinion, this is already the case. We might as well be more optimistic. Now the people of the whole country do not go out at home. They do not go to work during the Spring Festival. They are also delayed to work. Compared with the infection during normal work, Very lucky.
Wen / Wang Xinyu (Deputy Chief Physician, Department of Infectious Diseases, Huashan Hospital) Zhang Wenhong (Leader of Shanghai Medical Treatment Experts Group, Director of Infectious Diseases Department of Huashan Hospital)
(This article is reproduced from the "Huashan Infection" public account after authorization, and the copyright belongs to the Department of Infectious Diseases, Huashan Hospital, Fudan University.)
Editor-in-chief: Yunhui Yun
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