Q&A - Part 23
(Continued from May 23, 2020)
A: On February 5, China’s National Health Commission ( NHC) clearly stated that asymptomatic carriers could be the source of infection in the Protocol for Prevention and Control of Covid- 19 ( Edition 5). On March 26, at the meeting of the Leading Group of the CPC Central Committee for Prevention and Control of Covid- 19, Chinese Prime Minister Li Keqiang emphasized that special attention should be put to asymptomatic carriers and required NHC to analyze their contagiousness and conditions. On March 28, a new case infected by an asymptomatic carrier in Henan province raised concerns in China.
The virus can persist in asymptomatic carriers for more than 3 weeks. During this period, asymptomatic coronavirus carriers, like symptomatic patients, can infect others by droplets and direct contact. Based on a recent study, the contagiousness depends on the proportion of asymptomatic cases in the population, the amounts of virus being expelled, and the duration of expelling, as well as other factors such as patients’ occupation, behaviors, geographic scope of activities and sanitary measures.
No final conclusion has been reached about how contagious asymptomatic virus carriers are. In late January, several Chinese epidemiologists stated that asymptomatic carriers carry a lower amount of the novel coronavirus in their body, rendering themselves unlikely to be super- spreaders. However, other researches so far generally agree that the infectiousness of asymptomatic virus carriers differs little from confirmed cases. In a paper published in The New England Journal of Medicine on February 20, researchers of Guangdong Provincial Center for Disease Control and Prevention and other institutions warned about the infectiousness of asymptomatic carriers. These researchers found that the viral load detected in samples of asymptomatic carriers was similar to that in symptomatic ones. Another study conducted by Ningbo Municipal Center for Disease Control and Prevention with samples of Ningbo cases on March 4, suggests that the infectiousness of confirmed cases and asymptomatic carriers is not statistically significant.
It is worth noting that secondgeneration patients infected by asymptomatic carriers could experience severe symptoms. On January 27, China reported the first asymptomatic carrier who infected five other people and among them two developed into severe cases. In an article in SCIENCE CHINA Life Sciences, a researcher of Nanjing Medical University also pointed out that a close contact of an asymptomatic carrier in Nanjing developed into severe case one week after confirmation. Author: Liang Xiaomin
A: Urban communities and village communities are administratively defined units for social governance in China. Communities provide geographical space for residents’ daily activities. China adopted closed- off community management right after COVID- 19 broke out. Common measures include but are not limited to minimizing entrance numbers, setting up checking points, issuing entry permits, supervising face mask wearing, enhancing health monitoring and registering personnel and vehicles passing through. At the epicenter of the outbreak, communities enforce social distancing and travel ban by leaving one entrance open only. Residents are completely housebound or have limited opportunities to go outdoors. In areas where the outbreak is not severe, communities reduce the number of available entrances. Residents may enter or exist only with their entry permits. Non-residents are banned from entering.
The key to preventing and controlling COVID- 19 lies in communities. Adopting closed- off management appears to be a crucial method. It effectively decreases people flows, protects vulnerable populations and curbs virus spread. Daily activities of elders and children—both groups are vulnerable to COVID-19 infection due to weaker immune systems— generally happen in communities. ( To be continued on June 4, 2020)