What is an asymptomatic infected person

Starting from the last week of March, the national epidemic prevention measures have been upgraded. Austria, the Czech Republic, Slovakia, Bosnia and Herzegovina, Israel and other countries have issued mandatory mask wearing orders. The United States, which has always emphasized that healthy people do not need to wear masks, has also undergone major changes in its epidemic prevention policy. On April 3, the US Centers for Disease Control revised the recommendation to wear masks. The latest recommendation is that the public wear self-made cloth masks or scarves to cover the nose and mouth when going out. One of the reasons behind it is “asymptomatic infected people”, a term that is becoming a headache for the epidemic prevention departments of various countries. In China, starting from April 1, the situation of asymptomatic infections is included in the National Health and Health Commission’s daily outbreak report.

We all know that the “incubation period” of the new coronavirus in the body is about 14 days, which is also the number of days that various regions require mandatory isolation. Is an asymptomatic person the same as a patient with an incubation period?

The answer is slightly different, this word has some special meanings, it is also our latest understanding of this new coronavirus. Let me first use a flow chart to explain, if a person is unfortunately recruited and infected with the new crown virus, what are the possible results:

Note: The data cut-off date is April 3, 2020. The denominator of the percentage data in the figure is the total number of infected persons at the beginning of the period. This is the author’s synthesis of the data published by WHO, governments and relevant agencies, and the average value is taken within the approximate range. However, the new coronavirus is still a completely new disease, the sample size of the data is very limited, and early data in some countries do not count asymptomatic infections.

The epidemic prevention department refers to all patients who will eventually develop symptoms as the “latency period” before the symptoms appear, and all those who carry the virus but Patients who have no symptoms are collectively referred to as “asymptomatic patients.” ( Editor ’s note: According to the “New Crown Virus”Symptom Infected Persons Management Standards”, asymptomatic infection of New Coronavirus refers to no relevant clinical manifestations, such as fever, cough, sore throat and other symptoms and signs that can be self-perceived or clinically identifiable. Positive. There are two cases of asymptomatic infections: first, after 14 days of isolation medical observation, there are no symptoms and signs that can be self-perceived or clinically recognizable; second, the “asymptomatic infection” state in the incubation period. )

Which infected persons are infectious

In the above flow chart , who is infectious? ?

In the early stage of the outbreak of new coronary pneumonia, according to the past experience in the prevention and treatment of infectious pneumonia, especially SARS, it is believed that only patients with symptoms are infectious, which is very normal.

In the first four editions of the diagnosis and treatment plan issued by the National Health and Health Commission before February 5, the source of infection was written as “The source of infection seen today is mainly a new type of coronary “Pneumonia patients infected with viruses”.

On February 5th, the fifth edition of the treatment plan was released. Many people noticed that the description of the source of infection has changed a little. In this edition, A new sentence was added: “Asymptomatic people may also become the source of infection.” Everyone notices that the word used at this time is still “may”, that is, not sure. Until the seventh edition released on March 4, it is still this statement.

However, since March, more and more domestic and foreign studies have pointed out that people with asymptomatic infections are clearly contagious. I listed some of the more important research evidences I searched according to the timeline:

On March 1, a paper published in the Journal of the Chinese Medical Association It provides evidence of the spread of asymptomatic infections.

In a paper co-authored by scholars at home and abroad collected by the US Centers for Disease Control on March 12, the author studied a case of collective infection in a supermarket in Wenzhou, China , The data shows that this case may be spread by asymptomatic people.

On March 19, the authoritative international journal “New England Medical Journal” published a paper by a researcher from the Guangdong Center for Disease Control and Prevention, which also pointed out: asymptomaticInfectors have the potential to spread.

On March 31, the National Health and Health Commission officially released an official announcement: a series of questions and answers about whether the new coronavirus asymptomatic infection is infectious. Confirmed that asymptomatic infections are contagious.

At this point, the answer is becoming clearer. I still use the flow chart above to illustrate who is known to be infectious:

In the picture above, the red circle is confirmed to be infectious, and the green circle is not infectious. The only thing that can not be determined is that after the infection of the virus for more than 28 days Whether an asymptomatic person is still contagious. For the convenience of the following description, I call this group “long-term asymptomatic infected persons.”

On March 31, the National Health and Health Commission announced that from April 1, the National Health and Health Commission will announce asymptomatic infections in daily outbreak notifications.

New challenges brought by asymptomatic people

First of all, the policy of “healthy people do n’t wear masks” in many countries has lost important grounds. The reason why many countries, including the United States, does not require everyone to wear a mask even when an outbreak occurs, one of the reasons is that they not only cannot block the virus, but also give people a false sense of security and increase Risk of illness. But now the new problem is that it is difficult for people to judge who is a healthy person and who is an asymptomatic infected person, and the spitting stars that are normally spoken by asymptomatic infected persons may also be contagious. Therefore, wearing a mask has an important meaning: to prevent asymptomatic infections from spreading the virus. We see that from the last week of March, many countries have introduced mandatory mask wearing policies, and even the lead brother, the US Centers for Disease Control, has also revised the recommendations on masks.

Then, a bigger problem is that it becomes more difficult to identify and isolate the source of infection. When SARS became popular in 2003, all sources of infection were symptomatic patients, and their body temperatureElevated, it is easy to isolate the source of infection from susceptible people. I hate it now, a potential source of infection. Not only is it difficult for others to find him, but more troublesome is that he feels that he is a healthy person. He will walk around, socialize normally, and spread the virus unconsciously. This is why Jiaxian County, Henan found 3 asymptomatic infected persons, and after 3 normal working doctors, had to take measures to close the county, because it is difficult to immediately find out which of these 3 infected persons were passed to people.

Finally, there is a reasonable speculation that people returning from abroad and close contacts may be required to isolate medical observation for a longer period of time, or to do 100% nucleic acid testing to determine if it is an asymptomatic infection. Because just 14 days of isolation is no longer a guarantee that it will not become a source of infection.

Looking further, if those “long-term asymptomatic infections” (carrying the virus for more than 28 days or even longer) are proven to be infectious, then, the world All will face a very difficult ethical dilemma: do these people need to be isolated? From their own feelings, they are completely healthy people, but from the perspective of outsiders, they are also a potential source of infection. This is beyond the scope of pure medicine. Of course, it is best not to have this problem, hoping that people with long-term asymptomatic infections will not be infectious.

Treat rationally, do n’t panic

There are so many new challenges brought about by asymptomatic people to the prevention and control of the epidemic, but I I don’t want to give everyone the illusion that our country’s already stable epidemic will recur again. The purpose of my writing this article is to eliminate panic. We must pay enough attention to people with asymptomatic infections, but we cannot go to the other extreme and cause excessive panic. There are several reasons why you want to eliminate panic:

1. Asymptomatic people will not appear out of thin air for no reason. All asymptomatic infections must be people who have had close contact with the diagnosed patients or have been to the epidemic area. As long as these two types of people can be strictly traced, an effective line of defense can be built.

2. Although asymptomatic infected persons have no symptoms, they cannot escape nucleic acid detection. As long as the two types of suspected people mentioned above can be tested for 100% nucleic acids, all asymptomatic infections can be found. The epidemic situation in the country is now stable and there are sufficient detection kits. It is not difficult to perform 100% nucleic acid detection on suspected people.

3. According to the data in the flow chart above, we know that about 30% of the people infected with the virus are asymptomatic infected persons. (Editor’s note: asymptomatic infections at different stages of the epidemic development The proportions of people vary greatly. 30% is only an average calculated by the author based on past data.) Therefore, there can be no large number of asymptomatic infected people appearing out of nowhere in the society. If your city has been in a row for two consecutive weeks There are no newly confirmed cases, and the probability of asymptomatic infections around you is minimal. Professor Zhang Wenhong also focused on this point of view in an earlier interview.

4. Existing data shows that the asymptomatic infections are less infectious than the symptomatic ones. Based on the above four reasons, I suggest that you should remain rational in panic and use scientific thinking to face the new situation that emerges. Excessive panic is completely absent Necessary.

Be alert for a sudden drop in smell

So, is there any way to detect that you are an asymptomatic infected person?

At present, the “symptoms” of the “asymptomatic” mentioned in the prevention and control and diagnosis and treatment plan of the Health and Health Commission refers to dry cough, fatigue, fever, nasal congestion, flow Diarrhea, diarrhea, sore throat and other symptoms related to pneumonia.

But there is a noteworthy study, a paper published online on the Harvard University official website on March 28. Studies have found that the new coronavirus attacks key cells in the nose, potentially causing the infected person to lose their sense of smell. For example, after NBA player Rudy Gobert became infected with New Coronary Pneumonia, he sent a message on social media to wonder if other people, like him, have lost their sense of smell and taste. There are many cases like this, scattered on various social media.

Research groups have also confirmed this situation. For example, researchers from the British Association of Otolaryngology found through statistics. In Germany, more than two-thirds of cases of new coronary pneumonia have symptoms of loss of smell. In Korea, 30% of diagnosed patients have a sense of smell. In addition, more and more reports show that in the absence of other symptoms, the number of patients with a sense of smell has increased significantly.

This discovery is very valuable, it may help us to check whether we are infected with new coronavirus.

Based on this research, I would like to remind everyone that if during this time you suddenly find that your sense of smell has become obviously dull, you should actively isolate yourself, and then Try to do nucleic acid testing to determine if you are infected with new coronavirus.

(Author Wang Jie is the executive secretary of Science Voice and a popular science writer, author of “The Shape of Time”, “Strings of Starry Sky”, “Billions of Years of Solitude” “The Universe of Understanding”, “Children’s Scientific Thinking Training Book Series”, “The Lost Sky”, “Jingwei No. 9” and other books.