Sihai network

How is asymptomatic found? Is it contagious? Are there many asymptomatic infections in China?

How are asymptomatic infections found? Is it contagious? Are there many asymptomatic infections in China? What are the prevention and control requirements? The reporter of China Economic Weekly sorted out the issues most concerned by the people one by one.

Photography: Xiao Yi, Chief Photographer of China Economic Weekly

How are asymptomatic infections found?

Asymptomatic infections in COVID-19 are non related clinical symptoms, such as fever, cough, sore throat and other self perceived or clinically recognizable signs and symptoms, but respiratory tract specimens are positive for COVID-19 etiological tests.

At present, asymptomatic infections are found mainly through the following ways:

The first is to carry out active detection during the medical observation period for the close contacts of New Coronavirus pneumonia cases.

Based on the novel coronavirus pneumonia incubation period of about 14 days, there were cases of human transmission, and medical observation was conducted by close contacts in various organizations. As of 24:00 on March 31, 707913 close contacts had been tracked in China, and 20314 close contacts were still under medical observation.

The second is the active detection carried out in the investigation of aggregated epidemic situations.

For example, novel coronavirus pneumonia epidemic occurred in Jintan District of Changzhou City, Jiangsu province in February. According to the investigation of the expert group, asymptomatic infected persons play a major role in this aggregated epidemic.

The three is the active detection of the exposed population in the tracing process of infectious source of New Coronavirus pneumonia cases.

In the novel coronavirus pneumonia case, the asymptomatic infection may be detected when the exposure population is actively detected.

The four is to carry out active detection of travel history and residence history in some areas where New Coronavirus pneumonia cases continue to spread.

For example, since 0:00 on March 25 in Beijing, all entry personnel from Beijing port, regardless of destination, have been isolated and observed on site, and all have been tested for nucleic acid. Shanghai, Guangzhou, Chongqing and other cities have also taken similar measures.

By combing the public information, the reporter of China Economic Weekly found that in addition to the above four official ways to actively find asymptomatic infected persons, all localities have also taken the 'strictest' measures in history to comprehensively investigate asymptomatic infected persons.

For example, the Guangzhou Municipal Health Protection Commission recently issued a document calling on all medical and health institutions to carry out nucleic acid testing and screening for all new clinics or original hospitalized medical institutions of all beds in addition to outpatient visits to all fever clinics, and COVID-19 nucleic acid testing for outpatients and emergency patients with epidemiological history.

Photography: Xiao Yi, Chief Photographer of China Economic Weekly

Are asymptomatic infections contagious?

According to the monitoring data of close contacts carried out by the state and some provinces, there are second-generation cases of close contacts of asymptomatic infected persons. In the epidemiological investigation, it is found that individual aggregated epidemic situations caused by asymptomatic infected persons. Studies with a small sample size show that the viral load in the respiratory samples of asymptomatic infected persons is not much different from the confirmed cases.

Based on the current monitoring and research, asymptomatic infected people are infectious, but the length of infection period, infectious strength and mode of transmission still need further scientific research.

Some experts believe that in view of the fact that pathogenic nucleic acids can be detected in the respiratory tract specimens of asymptomatic infected persons, but due to the absence of clinical symptoms such as cough and sneezing, the chance of transmission caused by pathogen excretion is relatively less than that of confirmed cases.

According to who, 'based on available data, COVID-19 is mainly transmitted by patients with symptomatic symptoms', so asymptomatic infections may not be the main source of transmission.

Are there many asymptomatic infections in China?

Recently, academician Zhong Nanshan said that the current understanding of the situation of 'asymptomatic infected persons' in China is very limited, and there are neither specific figures nor detailed research. However, based on the known facts, some inferences can also be made.

In China, China has novel coronavirus pneumonia. However, the number of new confirmed cases of new crown pneumonia in China has not been rising, but it is decreasing. This shows that there is not a large number of asymptomatic infections in China.

If asymptomatic infection is found, network direct report shall be made within 2 hours

In January 28th, the national health and Health Committee issued the COVID-19 infection prevention and control plan (Third Edition), which included the asymptomatic infection of New Coronavirus in the prevention and control management. In the subsequent revision process, it made clear requirements for the reporting and management of asymptomatic infected persons.

If asymptomatic infection is found by various medical and health institutions at all levels, it shall be reported directly through the Internet within 2 hours. After receiving the report of asymptomatic infected persons, the county (District) level disease control institutions shall complete the case investigation within 24 hours, register the close contacts in time, and timely report the case questionnaire or investigation report through the infectious disease report management information system.

Asymptomatic infected persons shall be isolated for 14 days. In principle, those who have been isolated for 14 days and have negative nucleic acid detection of two consecutive samples (the sampling time shall be at least 24 hours apart) can be released from isolation; If the nucleic acid test is still positive, continue isolation medical observation. If any clinical manifestation occurs during isolation medical observation, it shall be transferred to confirmed case in time for standardized treatment. Asymptomatic infected persons and close contacts should also be subject to 14 days of centralized isolation medical observation.