How infectious is COVID-19? A new paper published in the Chinese Journal of Epidemiology provides new conclusions.
What is asymptomatic infection? According to the “COVID-19 Diagnosis and Treatment Plan (Trial Fifth Edition)”, asymptomatic infection refers to “positive COVID-19 virological test with no clinical symptoms and respiratory tract specimens.” In short, there is no fever and cough. , Fatigue, and other clinical symptoms, but COVID-19 virus nucleic acid test was positive, indicating that these people carry COVID-19 virus.
The infectious problem of asymptomatic infections has recently attracted outside attention. Zhang Wenhong, director of the Department of Infectious Diseases, Huashan Hospital affiliated to Fudan University and senior expert group leader of COVID-19 Shanghai expert treatment group, recently emphasized that after systematic observation, asymptomatic cases are increasing, so the next step should be more attention By.
The Chinese Journal of Epidemiology, Volume 41, 2020, recently published a paper “Analysis of Epidemiological Characteristics of Infections in Close Contacts of Ningbo COVID-19”. The infectivity of asymptomatic infection was analyzed.
The author of the study was Chen Yi and others from the Institute of Infectious Diseases, Ningbo Center for Disease Control and Prevention. The research investigated and collected all confirmed cases of COVID-19 virus pneumonia reported in Ningbo from January 21 to March 6, 2020. And asymptomatic infections reported information from epidemiological investigations and identified and tracked 2147 close contacts of all infected people.
The study found that a total of 110 of the 2147 close contacts developed confirmed cases, and another 22 were asymptomatic. The total infection rate of close contacts was 6.15% (132/2147), of which the close contact rate of confirmed cases was 6.30% (126/2001), and the close contact rate of asymptomatic infection was 4.11% (6 / 146), the difference in infection rates was not statistically significant.
So which close contacts are more likely to develop a confirmed case?
Studies have shown that COVID-19 is highly contagious, with high recurrence rates among family members, relatives, and friends, and is a high-risk group for infection. Among the different contact methods, co-living with patients and co-living infection rates are the highest, suggesting that prolonged unprotected close contact is a high risk factor for COVID-19 infection.
The study found that among close contacts, the infection rate was highest among friends / pilgrims (22.31%), followed by family members (18.01%). Medical personnel who were in close contact did not develop an infection. After excluding the incidence data of the “super communicator” event, the infection rate of friends decreased to 15.69%, which was lower than the infection rate of family members (17.54%), and the infection rate ranked second.
For pilgrim infections, one “super-spreader” occurred in Ningbo during the epidemic of COVID-19 virus pneumonia. The study found that the “super communicator” female was contagious within 1 day after the onset of the disease, and was mainly caused by sharing a special bus and participating in a Buddhist event. In the transmission of air-conditioned buses, there were 68 close contacts, 23 were diagnosed as confirmed cases of COVID-19, 2 were asymptomatic infections, and the infection rate was 36.76%.
According to the statistics of the different contact methods of close contacts and cases, the infection rate was the highest when living with the cases (13.26%), followed by the same transportation (11.91%). After excluding the influence factors of the “super communicator” incident, the infection rate of vehicle contact dropped to 1.80%. The rate of infections (7.18%) for dinners, gatherings, and card games were also high, as were relatively high levels of short-term face-to-face unprotected conversations or services (6.02%).
In addition, the investigation found that 4 cases were infected in the same medical environment as the confirmed cases for a long time during the hospital visit (1.94%); 5 cases were infected because they were in the same mall, assembly place or vegetable market as the confirmed cases. (1.16%).
Due to the greater risk of spread and spread of disease in close contacts, the paper suggests that the speed and speed of investigation of close contacts should be strengthened, strict close medical observation measures should be implemented for close contacts as soon as possible, and centralized isolation should be implemented as far as possible Medical observation to avoid transmission within the family.
In addition, studies have found that short, unprotected face-to-face conversations in outdoor environments can also cause disease transmission, suggesting that the disease is highly contagious. The author suggests that targeted health guidelines be developed to guide the public in personal protection.