Is it useful to disinfect the environment without leaving dead ends?

None of the scientific evidence supports it

Writing | Yan Xiaoliu

Source | “Medical Community” Public Account

In the fight against the epidemic in many places across the country since August, large-scale environmental sterilization has been implemented round after round.

Lhasa, Tibet carried out comprehensive grid elimination in the main urban area for 7 days.

The picture comes from Chinanews

Hebei Huailai used cleaning vehicles, spraying vehicles, spraying vehicles, and mist machines to eliminate 42 public places such as primary and secondary roads in the urban area.

The picture comes from Hebei News Network

Sanya, Hainan announced on August 23 that a total of 6 disinfection teams of “city + district” were established. According to the information of the Sanya Fire Rescue Detachment, comprehensive killings were carried out in designated areas such as train stations and community streets.

The picture comes from Sanya Fire Rescue Detachment

On August 25, Sanya’s first refitted fire and disinfecting vehicle drove into the jurisdiction, and the nine sprinkler heads continued to spray for 30 minutes. “Hainan Daily” said that it has greatly improved the speed of disinfecting, so that no dead ends are left in the whole region.

On the same day, Sanya issued the “Proposal on Home Disinfection for the Prevention and Control of the New Coronary Pneumonia Epidemic”, reminding the public that “home protection should be based on cleaning, supplemented by disinfection” and “there are no cases in the community. Just do your daily cleaning, you don’t have to sanitize every day.”

The picture comes from New Hainan

In response to measures such as large-scale spraying and fumigation of disinfectants, the consistent attitude of the World Health Organization (WHO) is that this is ineffective and may be harmful to health, irritating or damaging the eyes and respiratory system. or skin.

“The world’s major epidemic prevention agencies do not support large-scale environmental disinfection. At present, everyone emphasizes indoor ventilation and the number of air changes per hour to reduce the risk of virus transmission. Supported by scientific evidence, this is better than Environmental disinfecting is more important.” Jin Dongyan, a professor at the School of Biomedical Sciences, Faculty of Medicine, University of Hong Kong, told the “medical community”.

“Environmental Infection”, very unlikely

Comprehensive descriptions from multiple places, environmental disinfection has multiple tasks, including disinfection of Yang-related areas, flushing of urban public environments, and preventive disinfection of key places.

There are also regions that explicitly say “no” to environmental disinfection. In May of this year, Wang Jianhui, deputy head of the community prevention and control group of the Beijing New Crown Epidemic Prevention and Control Leading Group, said at a press conference that no matter whether the area is closed or controlled, extensive disinfection of the outdoor environment is not required to avoid excessive disinfection.

In July, the Shanghai Municipal Office of A&H emphasized that disinfection should keep in mind the “six nos”. Including directly spraying people without using disinfectants; not sterilizing outdoor air; not conducting large-scale disinfection of the external environment (greening, roads, walls, etc.) Do not use ineffective disinfection methods (such as fog machines, mist machines) for disinfection; do not use chemical disinfectants for air disinfection when there are people indoors; do not pour a large amount of disinfectant into the sewers and throw disinfectant tablets.

The guidelines for the use of disinfectants issued by the National Health and Health Commission in February 2020 also clearly pointed out that “seven inappropriate”, and Shanghai’s “six inappropriate” content overlaps.

Judging from the existing scientific evidence, it seems “superfluous” to rely on the environment to disinfect the virus and block the spread.

Viruses are pathogens that cannot survive alone. “The new coronavirus is an RNA virus and is very fragile. It usually deactivates within 30 minutes after leaving the human body. Considering the ventilation of outdoor air, it will also be deactivated.” Virology expert Chang Rongshan told the “medical community”.

In 2020, a study showed that in an outdoor environment, exposure to sunlight for 6.8 minutes will cause the new coronavirus in saliva to lose 90%% activity. In autumn and winter, to reach this level of inactivation, it takes 19 minutes of sun exposure.

This means that the new coronavirus cannot survive in the natural environment, or survive for a very short time, and basically will not cause transmission.

In July this year, the Joint Prevention and Control Mechanism of the State Council issued the “Notice on Further Optimizing the Prevention and Control of the New Coronary Pneumonia Epidemic of Imported Goods”, and no longer implements the new coronavirus on low-risk imported non-cold chain goods Nucleic acid testing and preventive disinfection. The notice also pointed out that under normal temperature conditions, the new coronavirus has a short survival time on the surface of most items, and is completely inactivated within 1 day.

“If there are basically no positive cases on a street, the amount of virus emitted into the air is very small, and if there is, it is quickly inactivated by sunlight. Outdoor killing is meaningless. There are many cases in the streets, but they have been closed and managed, so there will be very few viruses emitted, and outdoor disinfecting is meaningless.” “Phoenix Net” published an article by Zhang Hongtao, an American Ph.D. in pharmacology.

“Environmental disinfection is required”, what to do?

Professor Jin Dongyan told the “medical community” that in the early days of the fight against the epidemic, Hong Kong had taken environmental disinfection measures in public areas, such as apartment building corridors and elevators. Mainly wipe the surface with disinfectant, and have not done spraying, fumigation, etc.

WHO also mentions surface cleaning and disinfection in non-health care environments, etc.: “For the new coronavirus, if disinfectant is used, it should be wiped with a rag or wet wipe soaked in disinfectant. “

“In the early days, some places did use methods such as spraying and gas fumigation to carry out so-called deep disinfecting, but these have long been turned over.” He said that the new crown virus is transmitted by aerosols and droplets. host. The current epidemic prevention policies of many countries and regions emphasize air circulation.

In April of this year, a sub-journal of “Nature” published a study saying that the chance of the new coronavirus being transmitted through surfaces is 1/1000 of that transmitted through the air.

According to the “Guidelines for Air Change and Air Purification Equipment in Dine-in Dining Premises” issued in Hong Kong, all restaurants are required to achieve 6 indoor air changes per hour. This reduces exposure risk by up to 95%. Restaurants can also install air fresheners to ensure air quality.

Professor Jin Dongyan said that if there are more than 30 people infected in a restaurant, it is mostly a violation of ventilation regulations.

Germany requires public places such as schools to be ventilated regularly, or to use exhaust machines to achieve 7 air changes per hour.

my country’s “New Coronavirus Pneumonia Prevention and Control Plan (Ninth Edition)” also describes the ventilation of homes and vehicles. For example, open windows for ventilation 2-3 times a day, 20-30 minutes each time. However, there is no quantitative indicator for ventilation in public places.

Chang Rongshan told the “medical community” that my country’s current environmental technology can fully realize and eliminate virus-containing aerosols. A laminar flow ward in a hospital is an example. At the same time, the fresh air in the cabin of the passenger aircraft is designed so that there is always a one-way circulation of air in the three-dimensional space around each seat, and the space is exchanged at least 6 times per hour, and there is no dead space for ventilation.

However, it is difficult to implement related technologies to the level of civilian products. “This requires a large amount of ventilation and no dead ends. There are requirements for the airtightness of the room and the direction of air flow. If both are met, the cost will be very high.” He said.

Chang Rongshan also said that the use of vaccines to prevent infectious diseases has a history of hundreds of years, and the history of physical prevention and control is even longer, reaching thousands of years, but the effect of the latter has always been limited. Effective in emergency situations at the beginning of the outbreak. Once the virus spreads over a large area, it is ineffective.

At present, people live in high density and population mobility is high. It is necessary to strengthen public awareness and establish good hygiene habits. It is necessary to emphasize that no nose picking is required outdoors, avoid eating with dirty hands, and take the initiative when symptoms appear. seek medical attention. But epidemic prevention and control should mainly rely on vaccines.

“If we stay at the level of physical prevention and control, the epidemic may be endless.”


[1]Q&A: Considerations for cleaning and disinfecting environmental surfaces for COVID-19 in non-health care settings. World Health Organization

[2] Guidelines for the use of disinfectants. Supervision Letter of the National Health Office [2020] No. 147

[3] Huailai: Epidemic prevention and disinfecting to ensure the health of the masses. Hebei News Network

[4]Sanya Fire Fighting carried out comprehensive disinfecting and service guarantee work during the epidemic. Sanya Fire Rescue Detachment

[5]Anti-epidemic attack | Sanya Fire’s first modified spray and disinfecting vehicle hit the road to disinfect 9 nozzles at the same time. Nanhai Network

[6] Sanya uses the power of science and technology to find the right “prescription” and optimize the epidemic prevention measures. Hainan Daily

Source: Medicine

Editor in charge: Zheng Huaju

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