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Pneumonia: Does an asymptomatic infection cause a second outbreak

2019-nCoV Special
Source: bbc.com
[Life Information]     25 Mar 2020
As of 00:00 on 8 April, Wuhan, the center of China's new crown pneumonia epidemic, will lift control measures for the "exit from Han (Wuhan) from Hubei (Hubei) channel ". This means that the closure of the city begins on january 23rd. Officials across China have taken the lead in dining in restaurants to boost consumer confidence. People began to take off their masks and go outdoors for spring. Ev...

As of 00:00 on 8 April, Wuhan, the center of China`s new crown pneumonia epidemic, will lift control measures for the "exit from Han (Wuhan) from Hubei (Hubei) channel ". This means that the closure of the city begins on january 23rd. Officials across China have taken the lead in dining in restaurants to boost consumer confidence. People began to take off their masks and go outdoors for spring. Everything seems to be in order to resume production, back on track.

But three recent news reports have sent hidden signs to the public.

On the morning of march 24th, wuhan health and health commission announced that on march 23rd wuhan new confirmed cases, the patient is the people`s hospital of hubei province (headquarters) doctor. According to the Chinese media "Caixin" understand that the doctor on March 18 in the outpatient treatment of a new crown pneumonia asymptomatic infection.

Wuhan, the official Weibo "of the government of Wuhan, issued a" important notice "about 1 am on March 22, saying that on the afternoon of March 20, a resident of Wuhan`s" Lishui Kangcheng District with new cases "was confirmed to be an" asymptomatic infected person ". According to China`s Circular of the General Office of the State Health and Health Commission on the issuance of a new coronavirus pneumonia prevention and control programme (sixth edition), there are non-diagnosed cases.

On march 20th, the news circulated on the internet, china`s hubei province`s new crown pneumonia epidemic prevention and control headquarters issued a notice on the state and provincial teams for the prevention and control of disease and control in e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e-e

From march 17th, medical teams from china`s provinces to help wuhan began to withdraw. As of march 20,12000 people had been evacuated, according to the chinese media, caixin.

In this context, the provincial aid Hubei prevention and control team suspended the evacuation notice and let the public tense nerves. The "Notice ", which suspended the evacuation of Hubei Province, explained that this was" to further do a good job in the prevention and control of the epidemic situation of new crown pneumonia in our province, combined with the actual situation of the epidemic situation in our province ".

Chinese media "Caixin" quoted the insider of China`s CDC as saying that the suspension of the withdrawal of the ranks of disease control departments is the national level "temporarily uneasy about the situation in Wuhan and Hubei ", so that the epidemic prevention team stay for a few days to remain on guard. More worrying is the case of asymptomatic new coronavirus infections. If the zero increase in confirmed cases can be maintained and stabilized, the next step of the disease control team can withdraw.

"A few or a dozen asymptomatic positive cases can still be detected every day, and it is not possible to judge whether the transmission in Wuhan has been completely blocked ," said the insider.


Who is asymptomatic infected? 

China`s state health and health commission`s new coronavirus pneumonia prevention and control program was updated to march 6th edition. An asymptomatic new coronavirus infection refers to those who have no clinical symptoms (such as fever, cough, sore throat, etc.), respiratory tract and other specimens of new coronavirus etiology or serum lgM antibody test positive.

In the sixth edition of the prevention and control program, asymptomatic infected persons are not included in the confirmed cases, but are reported separately as an independent category in the online direct report and will not be published to the public.

And asymptomatic infected person if appear clinical symptom, want to revise to confirm case in time. After the discovery of asymptomatic infected people to focus on isolation for 14 days, two nucleic acid tests negative to remove isolation.

At the operational level, the Wuhan government 22 Day statement did not mention whether to isolate the asymptomatic infected person for 14 days.

Wuhan, the center of China`s new coronavirus outbreak, will lift control measures for the exit from China`s Han and Hubei provinces from 00:00 April 8


How many asymptomatic infections are there? 

Public awareness of the epidemic has deepened with the advancement of medical and scientific research.

Also on march 20th, an article published in nature (Nature), the world`s leading academic journal, said mild or asymptomatic infections could account for 60% of all new coronavirus infections. As of March 24, China has diagnosed more than 80,000 new cases, with about 290,000 outside China.

A large number of scientists suspect there is an undiscovered pool of hidden venereal disease, as more and more infected people have no history of close contact with confirmed cases and have not been to the outbreak site. The severity of the phenomenon and its role in the transmission of the virus remain elusive because most mild patients are not yet seeking medical assistance because of their mild symptoms and may also avoid screening methods such as body temperature tests.

According to the authors, asymptomatic infections are different from previously unreported cases, which are at an "early clinical stage" where government lack of medical resources can not be diagnosed or is not apparent.

"An understanding of the proportion of asymptomatic or mild patients is important for us to understand what causes this particular epidemic ," said Ostholm (Michael Osterholm), director of the Center for Research and Policy on Infectious Diseases at the University of Minnesota. "

to assess the extent of sexy infection, a group of researchers in china and the united states developed a model using clinical data from 26000 laboratory confirmed cases received by wuhan health committee.

The group`s researchers, published in the March 6 medical preprint medRxiv, found that 37400 people had been infected with the new crown virus in Wuhan as of February 18, but authorities did not know. Most of these unreported cases are mild or asymptomatic.


How does asymptomatic infected person spread power? 

An article published by the Guangdong CDC in the New England Journal of Medicine (NEJM) on March 19 shows that patients with new crown pneumonia have detected high viral load shortly after onset, and one infected person has never shown symptoms, but the amount of virus he releases is the same as the patient with symptoms.

These data confirm the speculation of many scientists that some infected persons are "highly contagious when mild or asymptomatic ". However, the specific severity remains unclear. A study of more than 700 infected children nationwide by the Shanghai Children`s Medical Center found that 56 percent of children had mild or asymptomatic conditions. Many scientists worry that this will lead to an underestimation of children`s susceptibility to new crown viruses.

Zhang Wenhong, director of the Huashan Hospital Infection Department affiliated to Fudan University, quoted the Global Times as saying that the proportion of asymptomatic infections is very low, the amount of virus carried is also small, the spread of harm is relatively small, will not become a "super communicator ". "Super Communicator" is historically a severe patient. But he cautioned that asymptomatic infections do not mean they are not contagious, and there is a certain probability that they will be transmitted to close contacts.

According to nature`s article, mild or asymptomatic infections do not have a weak ability to spread the virus, and such hidden sexy infections could trigger a new outbreak.

Wuhan Health and Health Commission issued a notice at 11 p.m. on March 23 to respond to the public concern about asymptomatic infected people, pointed out that asymptomatic infected people can also become a source of infection, with a certain risk of transmission. However, according to the World Health Organization ," based on available data, the new coronavirus is mainly transmitted by patients who have developed symptoms ", so asymptomatic infections may not be the main source of transmission.

But who has been criticized for its slowness, inefficiency and lack of influence in the prevention and control of the epidemic.


What epidemic prevention measures should be taken for asymptomatic infected persons? 

If these findings hold, researchers in nature`s article say urgent measures are needed to control mild and asymptomatic cases that fuel the pandemic. Closing schools, eliminating public gatherings, keeping people at home and away from public places, these powerful social isolation measures are the only way to stop the spread of these asymptomatic cases.

Zhong Nanshan, head of the high-level expert group of China`s National Health and Health Commission, said earlier that 50 percent of imported cases abroad had no fever and that only symptoms like colds, such as cough, were detected after nucleic acid tests.

China now requires all those returning from abroad to observe 14 days of isolation, during which time symptoms are observed. Once symptoms are present, close contacts are also observed in isolation.


What is a "pandemic "? 

Weng Jianping, a professor of public health co-laboratory of the Anhui Provincial Health and Health Commission of China and the University of Science and Technology of China, told the China Science News in early March :" From the current prevention and control effect, this kind of does not cause a very wide spread phenomenon. The newspaper also noted the high social cost and difficulty of segregated observation of suspicious contacts.

There are now warnings in the medical community that the new crown virus may coexist with humans for a long time. Weng Jianping believes that this is also based on research observations of past pandemic viruses, such as influenza virus asymptomatic carriers reaching 5.2%-35.5%, and a study of human rhinovirus shows that asymptomatic infections are four times more than symptomatic infections.

From an evolutionary perspective, mr weng says most infectious venereal disease pathogens tend to develop in the direction of increased transmission and reduced virulence, but whether the new crown virus follows this rule is uncertain.

Wuhan Health and Health Commission, responding to individuals` risk of infection from asymptomatic infections, said that for the general population, wearing masks, keeping distance, washing hands frequently and not gathering are the most effective means of protection

The top academic journal Nature recommends social grooming for both mild and asymptomatic infections. But as work resumed, the Chinese public began to remove masks and return to workshops, companies, restaurants and parks.

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