The researchers said that their findings did not show that the virus couldn’t be passed on by asymptomatic carriers, and they didn’t suggest that their findings were generalisable.
They said that strict measures—such as mask wearing, hand washing, social distancing, and lockdown—were successful in reducing the virulence of SARS-CoV-2 in Wuhan and that asymptomatic people in Wuhan may have low viral loads. This means that the finding cannot be applied to countries where outbreaks have not been successfully brought under control.
Fujian Song, from UEA’s Norwich Medical School, who collaborated with colleagues in Wuhan on the research, said: “The asymptomatic cases identified in the screening programme were truly asymptomatic, as none of them showed clinical symptoms before or during their follow-up isolation.” But, he added, “there is plenty of evidence elsewhere showing that people infected with covid-19 may be temporarily asymptomatic and infectious, before going on to develop symptoms.”
Using antibody testing, the researchers found that almost two thirds of the asymptomatic cases had previously had covid-19. “With the centralised isolation and treatment of all covid-19 cases during the lockdown period in Wuhan, the risk of residents being infected in the community has been greatly reduced. When susceptible residents are exposed to a low dose of virus, they may tend to be asymptomatic as a result of their own immunity,” wrote the authors.
Song said, “It is very important to say that these asymptomatic cases were identified shortly after the relaxation of a very stringent lockdown in Wuhan that lasted more than 70 days. By then, the epidemic in Wuhan had been effectively brought under control. It is too early to be complacent, because of the existence of asymptomatic positive cases and high level of susceptibility in residents in Wuhan.”
(From elsewhere discussing the study...)
The researchers said that their findings did not show that the virus couldn’t be passed on by asymptomatic carriers, and they didn’t suggest that their findings were generalisable.
They said that strict measures—such as mask wearing, hand washing, social distancing, and lockdown—were successful in reducing the virulence of SARS-CoV-2 in Wuhan and that asymptomatic people in Wuhan may have low viral loads. This means that the finding cannot be applied to countries where outbreaks have not been successfully brought under control.
Fujian Song, from UEA’s Norwich Medical School, who collaborated with colleagues in Wuhan on the research, said: “The asymptomatic cases identified in the screening programme were truly asymptomatic, as none of them showed clinical symptoms before or during their follow-up isolation.” But, he added, “there is plenty of evidence elsewhere showing that people infected with covid-19 may be temporarily asymptomatic and infectious, before going on to develop symptoms.”
Using antibody testing, the researchers found that almost two thirds of the asymptomatic cases had previously had covid-19. “With the centralised isolation and treatment of all covid-19 cases during the lockdown period in Wuhan, the risk of residents being infected in the community has been greatly reduced. When susceptible residents are exposed to a low dose of virus, they may tend to be asymptomatic as a result of their own immunity,” wrote the authors.
Song said, “It is very important to say that these asymptomatic cases were identified shortly after the relaxation of a very stringent lockdown in Wuhan that lasted more than 70 days. By then, the epidemic in Wuhan had been effectively brought under control. It is too early to be complacent, because of the existence of asymptomatic positive cases and high level of susceptibility in residents in Wuhan.”