How contagious is a symptomatic infection? CDC: 1/3 of confirmed cases

On April 2, the Joint Defense and Control Mechanism of the State Council held a press conference on the prevention and control of the new coronary pneumonia outbreak and the work of international cooperation in medical care. Recently, asymptomatic infections have aroused high concern from all walks of life. At present, the academic community on the problem of the spread of asymptomatic infection, and even media reports that asymptomatic infections may cause a new outbreak in China. Asked by a reporter how to view the problem of the spread of asymptomatic infections, what is the impact on the prevention and control of future outbreaks?

In response, Wu Zunyou, chief epidemiologist of the Cdc, said that asymptomatic infections are tested positive through nucleic acids but do not have any clinical symptoms.

How contagious is a symptomatic infection? CDC: 1/3 of confirmed cases

“So is he contagious?” How contagious is it? What role does it play in the spread of the epidemic? Wu Zunyou said that the previous two days in the Chinese Journal of Epidemiology, a pre-printed article, this study was carried out by the Ningbo CDC, the center of the confirmed patients close contacts and asymptomatic contacts of close contacts to see the incidence of the two groups.

Wu Zunyou believes that the study has two important public health tips. First, the above-mentioned studies found that on average, nearly three patients per confirmed patient were able to spread, and on average, less than one patient per asymptomatic infection. In other words, the transmission efficiency of asymptomatic infections is about 1/3 of the confirmed cases, which is from the individual level.

Second, from the group level, the number of cases transmitted by asymptomatic infections accounted for only 4.4% of the total number of cases, less than 5%, that is, from the group level, asymptomatic infections contribute relatively small to the spread of the epidemic.

Wu Zunyou said that other provinces have also done some research, in a southern province conducted a larger study showed that more than 1500 asymptomatic people close contact, 7 people became ill, but further investigation and analysis, found that these 7 people not only contact with asymptomatic infected people, but also contact with the confirmed patients.

“That is to say, it cannot be assumed that it is caused by asymptomatic infections. This common exposure, if not carefully investigated, has the potential to expand the judgment of the ability of asymptomatic infections to spread. We now have very limited data on the transmission period, transmission capacity and contribution of asymptomatic infections, and more research and observation are needed in order to gain more understanding and understanding of such phenomena. He said.

How do asymptomatic infections occur? Wu Zunyou stressed that all asymptomatic infected people must have a history of contact with the confirmed patient, or he has been to the epidemic area, for the epidemic has occurred but the confirmed cases have been cleared more than two weeks of the region, will not appear for no reason asymptomatic infection.

“Our current measures should be said to be able to detect in time, timely control of asymptomatic infections, by asymptomatic infections caused by the possibility of epidemic is very small, will not cause social-level spread. Wu Zunyou said.