Shanghai hospital addresses asymptomatic infection concerns

The department of infectious diseases at Shanghai Huashan Hospital Affiliated with Fudan University published an article titled "How to interpret asymptomatic infection cases (of COVID-19) and how should we cope with the situation?" on its official account on WeChat on Tuesday.

The following is an excerpt of the article.

Q: Why do we believe that when the number of local confirmed cases decreases sharply, there will no longer be a large number of asymptomatic infection cases?

A: Asymptomatic cases of COVID-19 refer to those who do not show clinical symptoms, such as fever, cough and pneumonia, but are tested positive for the novel coronavirus through nucleic acid testing.

Studies so far have shown that such cases are also contagious.

We first need to understand that asymptomatic patients and symptomatic ones coexist for many infectious diseases, including COVID-19. Some domestic and foreign studies have suggested that the rate of asymptomatic cases account for 18 to 31 percent of total infections. These may include people showing slight symptoms during quarantine period which were not observed.

The rate also showed that asymptomatic cases exist together with a larger number of symptomatic cases, and they do not exist independently. That's why Zhong Nanshan, an academician with the Chinese Academy of Engineering and a prominent expert in respiratory diseases, said that "the number of new confirmed COVID-19 cases continues to drop in China, and that means the number of asymptomatic cases in the country is not large".

Q: How do we understand the risk that asymptomatic cases pose to the country?

A: The risk of a large-scale community spread of the virus caused by asymptomatic cases in the country remains low. The main reason is that if the number of new infection cases in a region remains small, the number of asymptomatic cases is also small.

Under such circumstances, what we need to do is to carry out thorough testing and timely quarantine for the close contacts of confirmed cases. Even if there are a small portion of asymptomatic cases among them, we can find them through nucleic acid testing.