Focus on the new crown aerosol: closed environment may be generated, further research is needed
Recently, a study published by the international top academic journal "Nature" detected the RNA of the new coronavirus in the air, which once again raised concerns about whether the new coronavirus may be transmitted through aerosols.
The above study conducted environmental monitoring on two hospitals in Wuhan and some public areas, and the results showed that under strict control and control conditions at that time, the two hospitals and the public environment were generally safe. However, in the toilets used by patients, the aerosol virus load is relatively high, suggesting that the patient's toilet flushing process may be an important source of viral aerosols; certain people can be detected near supermarkets and hospital building passages where people are crowded The aerosol virus load indicates that there is a potential risk of aerosol transmission between the virus carrier and the surrounding population when people gather. The study did not investigate whether the new coronavirus RNA is potentially infectious.
Aerosol transmission refers to the nucleus of protein and pathogens left by the water droplets lost during the air suspension process, forming aerosol nucleus, which can float to a distant place in the form of aerosol, causing long-distance transmission.
At present, there is no evidence that the new coronavirus is transmitted by aerosol, and there is no evidence to completely deny the existence of this transmission. Some studies have shown that the new coronavirus can survive in aerosols, and there are individual cases suggesting the possibility of aerosol transmission of the new coronavirus. Nevertheless, the Ministry of Science and Technology believes that the role and place of aerosol transmission are limited, and that ordinary people have little risk of aerosol infection in a well-ventilated daily environment.
Relatively closed environment may spread through aerosol
On March 5, the Hunan Provincial Center for Disease Control and Prevention reported in the "Journal of Practical Medicine" an epidemiological survey of a new crown-aggregated epidemic transmitted by aerosol in public transportation. At the time, the study believed that the outbreak was spread by public transportation and found that the new coronavirus spread in the air-conditioned air-conditioned compartment up to 4.5 meters. The virus can float in the air for at least 30 minutes and cause infection. The research team reminded that the new coronavirus has a strong ability to spread and can be spread through aerosols in a closed environment.
However, the paper has now been withdrawn. The first author of the paper, Hunan Provincial Center for Disease Control and Prevention, Luo Luowei explained to Peng Mei News, "Some details are not perfect, we intend to submit after perfecting." The details here " The main reason is that the entire investigation process is not complete enough. For example, whether these people are moving on the road and whether they are in contact with each other before entering the car are actually critical. "
On March 17, a study published in the "New England Journal of Medicine" by the National Institutes of Health, the Centers for Disease Control and Prevention, the University of California, Los Angeles and Princeton University showed that the new coronavirus can survive in aerosols3 hour.
In terms of specific infectious cases, Harbin City, Heilongjiang Province, has witnessed an inter-provincial epidemic spread since April 9th. By April 17, the virus infection chain had infected at least 42 people in Harbin. Zeng Guang, a member of the high-level expert group of the National Health and Health Commission and chief epidemiology of the Chinese Center for Disease Control and Prevention, said in an interview with the media on this matter that he has always emphasized the transmission of droplets. In this incident, aerosol transmission should play a very important role. effect.
Li Lanjuan, academician of the Chinese Academy of Engineering, member of the high-level expert group of the National Health and Health Commission, and Hou Jinlin, director of the Liver Disease Center of the Southern Hospital of Southern Medical University and director of the Guangdong Liver Disease Research Institute, discussed the possibility of the spread of the new coronavirus through aerosols in mid-April.
Hou Jinlin stated on April 16 that the new coronavirus infection is mainly transmitted through the respiratory tract, and there is a possibility of aerosol transmission in a relatively closed environment. On April 18th, Li Lanjuan said in a video connection interview program that the new coronavirus can be transmitted through droplets and aerosols. It is highly contagious, and most people have not been exposed to or infected with the new coronavirus, so all People are susceptible to the new coronavirus. Only by controlling the source of infection, cutting off the transmission route, and protecting susceptible people can the epidemic be controlled.
The statements of the two experts are basically consistent with the expression of the "New Coronavirus Pneumonia Diagnosis and Treatment Program (Trial Sixth Edition)". In the "New Coronavirus Pneumonia Diagnosis and Treatment Program (Trial Sixth Edition)" released by the National Health and Health Commission on February 19, in terms of transmission routes, the original official statement that "the transmission routes of aerosols and digestive tracts are yet to be defined" is changed to "There is a possibility of aerosol transmission in a relatively closed environment when exposed to high-concentration aerosols for a long time."
Well-ventilated environment with little risk of aerosol infection
Although some scientists believe that there is a possibility of the spread of the new coronavirus through aerosols, the Ministry of Science and Technology and WHO have stated that the conditions for the spread of aerosols are limited, and the general public is not at high risk of contracting the new coronavirus via aerosols.
On February 28, Wu Yuanbin, director of the Department of Social Development and Technology of the Ministry of Science and Technology, said at the press conference of the Joint Defense and Joint Control Mechanism of the State Council that the findings of the study so far show that respiratory droplets and close contact are still the main transmission routes.
"In response to the problem of aerosol transmission, the Laboratory Animal Institute of the Chinese Academy of Medical Sciences has also carried out corresponding transmission experiments, suggesting that aerosol transmission must simultaneously meet the three conditions of confined space, long time, and high concentration of virus. In extreme conditions It is only possible to spread aerosols. "
He said that ordinary people in the well-ventilated daily life environment have almost no risk of aerosol infection.
Liang Wannian, head of the Chinese side of the China-World Health Organization Joint Expert Investigation Team for New Coronary Pneumonia and the team leader of the National Health and Health Commission for New Coronary Pneumonia, pointed out to CCTV News on March 1 that the joint investigation report believes that the main way of transmission of new coronary pneumonia Two, droplet transmission and contact transmission. Contact transmission is mainly in close contact transmission. There is no evidence of airborne transmission (that is, aerosol transmission), but there is no evidence to completely deny the existence of such transmission. But even if it exists, its role and place are limited. For the general public, its spread value is not great.
The World Health Organization also stated on March 30 that, based on current evidence, coronavirus disease 2019 is mainly transmitted from person to person through respiratory droplets. In the analysis of 75,465 patients with 2019 coronavirus disease in China, no cases of airborne transmission have been reported.
Surging News Reporter Zhang Wei