Mar 18, 2020 08:00:00

Novel coronavirus may be spread by infected individuals without subjective symptoms

The new coronavirus infection (COVID-19) is rapidly spreading and has been recognized by the

World Health Organization (WHO) as a pandemic for the first time in about 11 years . Regarding the cause of the rapid spread, Li Ruiyung, a researcher at the Imperial College London MRC Center , reports that infections may have been rapidly spread by people without subjective symptoms.

Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2) | Science
https://science.sciencemag.org/content/early/2020/03/13/science.abb3221

In the case of a new type of coronavirus infection, in the absence of mild or almost no symptoms and no subjective symptoms, many viruses are spread by infected people who do not wear masks or go out carelessly. It may have been. To estimate when the number of people without asymptomatic infections increased, Rui Yun reported that the number of people without asymptomatic infections in China before January 23, 2020, when travel to Wuhan was restricted. Was estimated.

The simulation of the spread of the new coronavirus by Rui Yun takes into account the spread of infection by people traveling between cities. The number of people traveling between cities is calculated from data based on the

number of travelers during the Spring Festival of 2018 (about 2.97 billion in total).

The following graph is a simulation of the increase in the number of infected people in China (A), Wuhan City (B) and Hubei Province (C) from January 10, 2020 to January 23, 2020. The vertical axis represents the number of infected people per day, the horizontal axis represents the date of January 2020, and the blue graph represents the total number of infected people, including those without subjective symptoms. The vertical box in the blue graph indicates the interquartile range , and the horizontal line in the box indicates the median. The red crosses indicate the actual number of infected cases reported by day. The graph suggests that around January 11, 2020, the number of infected individuals, including those without subjective symptoms, may have been greater than those reported.

The

ensemble Kalman filter was used to calculate the increase in the number of infected people, and the results derived from 300 simulations are graphed.

Simulations show that between January 10 and January 23, 2020, there were 13,118 infected people in Wuhan and 16,829 in China, including cases without subjective symptoms. It has been. From this result, Mr. Ruiyun said, `` If there are fewer infected people without subjective symptoms, that is, if we can find 'infected people without subjective symptoms' earlier, the infection reported by January 23, 2020. Would have decreased by about 78% in China and by about 66% in Wuhan. '

It has also been shown that there was an average 6.6 day delay across the country from infection with the new coronavirus until diagnosis.

Ruiyun claims that early detection and isolation of infected individuals is effective in fully controlling the spread of the new coronavirus. In addition, due to the increased coverage and awareness of the new coronavirus, it is thought that the proportion of people who are diagnosed in hospitals is increasing, and that awareness among medical professionals is also increasing, so it was overlooked in the past. It is thought that the ability to correctly diagnose a case has been improved. `` There is a possibility that the spread of infection could be further delayed, '' said Ruiyun, as government measures such as increasing the use of masks, limiting travel, closing classes, and isolating infected people are steadily progressing. You.