What is asymptomatic infection? Will it become a new source of infection? How to find, manage and prevent? Put together a question and answer post on the latest authoritative information and expert opinions, and look at it together.
1. What is asymptomatic infection of COVID-19 virus?
According to the latest definition of the National Health and Medical Commission, asymptomatic infection of COVID-19 virus refers to those who have no relevant clinical symptoms, such as fever, cough, sore throat, and other self-perceivable or clinically identifiable symptoms and signs, but specimens such as respiratory tract Those who tested positive for viral pathogens.
Asymptomatic infection is usually divided into two situations: one is that the nucleic acid test of the infected person is positive, and after 14 days of incubation period observation, it is always asymptomatic; the second is that the nucleic acid test of the infected person is positive, and then there is some clinical manifestation, namely Incubation period asymptomatic infection.
Many of the well-known infectious diseases have asymptomatic infection, such as viral hepatitis B and AIDS.
2. How are people with asymptomatic infection found?
Asymptomatic infections are almost never detected by active consultation because they have no clinical symptoms.
At present, most of them are found through active monitoring by relevant departments. There are four main ways: first, medical observation of close contacts, second, investigation of cluster epidemics, third, tracking of the source of infection, and fourth, some domestic and overseas COVID-19 cases. Continue to disseminate the travel history or residence history of the area.
3. What is the proportion of asymptomatic infection? Who will be infected?
The incidence of asymptomatic infection is currently difficult to ascertain, and there are large differences in case reports in different regions, different clustering methods, and different populations.
According to a paper published by researchers from the China Centers for Disease Control and Prevention in the Chinese Journal of Epidemiology, as of February 11, the center has received a total of 56,128 domestically reported positive test cases and clinically diagnosed cases, including 889 asymptomatic infections. The ratio is about 1.6%; an article published in the “Nature” magazine on March 20 mentioned that COVID-19 may have a maximum of 60% asymptomatic and mild patients.
According to the latest tweet from the Department of Infectious Diseases, Huashan Hospital affiliated to Fudan University on March 30, taking some existing studies as an example, among people infected with COVID-19 virus, the proportion of asymptomatic infection is about 18% -31%, “Assumption 10 Individuals who are exposed to the virus may end up with 6-8 people, 2-4 people will never get the disease or the symptoms are very mild. ”
Asymptomatic infection occurs more frequently among close contacts of confirmed cases of COVID-19, and close contacts of foreign personnel, and high recurrence rates among family members, relatives, friends (especially children); among different contact methods, The confirmed cases have the highest infection rate of living together and living together.
4. How infectious is the asymptomatic person?
Asymptomatic infection is contagious. Second-generation cases have continued in close contacts, and epidemiological investigations have also found clustered outbreaks caused by asymptomatic infections. Small sample studies have shown that viral load in respiratory samples from asymptomatic infections Not much different from confirmed cases.
The academic community has no consensus on the length of infection, infectivity, and transmission methods of asymptomatic infections. Zhang Wenhong, director of the Department of Infectious Diseases, Huashan Hospital, Fudan University believes that asymptomatic infections can be prevented within 14 days after infection. The virus has been in the body for more than three weeks and has the possibility of infection. Some experts believe that asymptomatic infections have no symptoms such as cough and sneezing, and there is less chance for pathogens to be transmitted outside the body and cause transmission.
Regarding the situation of asymptomatic infections in China, Academician Zhong Nanshan said that he has limited knowledge at present, neither specific numbers nor detailed studies; but generally speaking, the infection rate of asymptomatic infections in people who are in close contact with him is high, and “China recently The number of new confirmed cases of COVID-19 not only has not increased, but has continued to decline, which can indicate that China does not have a large number of asymptomatic infections. ”
5. How should people with asymptomatic infection be reported and managed?
Since the National Health and Health Commission’s “Pneumonia Prevention and Control Plan for New Coronavirus Infection” (Third Edition), asymptomatic infections have been included in the prevention and control management system. All types of medical and health institutions at all levels find asymptomatic infections, and should report directly to the network within 2 hours; county (district) level disease control institutions should complete case investigations within 24 hours after receiving reports of asymptomatic infections, and pass the infection in a timely manner. Report on the disease report management information system.
Asymptomatic infection should be isolated for 14 days. In principle, those who have been separated for 14 days and have negative nucleic acid tests on two consecutive samples (sampling interval at least 24 hours) can be released. If there are clinical manifestations during isolation medical observation, they should be promptly referred to a confirmed case. Close contacts of asymptomatic infected persons also need to be concentrated for 14 days.
At present, Zhejiang Province has launched “14 + 14” days of isolation for asymptomatic infections (14 days of centralized isolation medical observation at designated hospitals, after the release of isolation, transfer to the centralized isolation point to continue observation for 14 days).
On the one hand, by strengthening the isolation, testing, and tracing of all close contacts of patients diagnosed with key groups with special requirements in China, the risk of community transmission of asymptomatic infection will be reduced; on the other hand, nucleic acid testing will be performed on all immigrants. After asymptomatic infection is found, an epidemiological investigation can be conducted in time to prevent the outbreak of “asymptomatic” foreign disease in the country to a certain extent.
6. How do people protect themselves from the risk of asymptomatic infection?
Some people worry that they may be infected asymptomatically, and some worry that they may be asymptomatic. Although asymptomatic infections are not easy to detect and infectious, they can only become infected if they are in close contact with nucleic acid-positive asymptomatic infections without protection. Prevent yourself by keeping a safe social distance, washing your hands frequently, and wearing a mask.
If you have been in close contact with an infected person, you should contact the local medical institution in a timely manner. If the nucleic acid test is positive and there are no symptoms, you need to cooperate with the disease control personnel to conduct isolation and observation;
For those who have no history of close contact with COVID-19 virus infection and who have no symptoms, there is no need to test.