Yuan Lei told you | Is aerosol transmission air transmission? Protection pay attention to these points

Release time:

2024-01-29 09:38


Yuan Lei told you | Is aerosol transmission air transmission? Protection pay attention to these points


What is an aerosol?

To put it simply,Aerosols are ultra-small particles suspended in the air that can also cause disease.


To understand aerosol transmission, it is necessary to first explain airborne transmission.


Airborne transmission refers generally to the inhalation of tiny particles containing pathogens in susceptible populations. With the development of detection technology, people have found that when talking, coughing or sneezing, they can detect smaller particles on the sub-micron and super-micron scale.



Due to such a deepening understanding of airborne transmission, scientists further proposed the broad concept of aerosol (aerosol): refers to all solid and liquid particles (0.001 to 100 microns in diameter) suspended in a gas (such as air).



Is aerosol transmission airborne?


Maybe everyone has had this experience: walking in the corridor or even on the road, there is no one within tens of meters around, but you can still smell the smoke. What we smell is the particles of a few hundred nanometers or so formed by the burning of tobacco.


The smaller the particles, the more obvious the viscous effect of air. The micron-sized particles in the air are like sesame seeds sprinkled in honey and hardly sink. Quantitatively, the residence time of small particles at the same height in still air is inversely proportional to their surface area. For 1 micron particles, the settling time in still air is more than 1 hour. And there is always wind and grass in the environment, so these particles almost never settle, always stay in the air. This is also why smokers may have disappeared, but the aftertaste is still long gone.

The size of the droplet nuclei containing the new coronavirus is in the sub-micron to micron range, similar to the particle size after tobacco combustion. As a result, droplet nuclei can remain suspended in the air for a long time and drift far away, fueled by turbulence in the air. Coronaviruses in droplet nuclei are protected by a protein membrane shell that may remain active for a considerable period of time. If it is inhaled, it may lead to infection with new coronavirus.


So is aerosol transmission = airborne?


Feng Luzhao, director of the Respiratory Infectious Diseases Department of the Chinese Center for Disease Control and Prevention, explained that airborne transmission (Airborne transmission) refers to the spread of diseases caused by the invasion of new susceptible hosts through the air after the pathogen is discharged from the source of infection. The main mode of transmission. Broadly speaking, airborne modes of propagation include droplets, droplet nuclei, and dust.


In a narrow sense, airborne transmission only refers to the transmission caused by the spread of pathogen particles with a diameter of less than 5 microns that can be suspended in the air for a long time to a long distance in the form of aerosols, including droplet nuclear transmission and dust transmission.
The narrow concept of airborne transmission can be divided into two categories:

(1) Mainly transmitted by air, which means that it can be transmitted through a variety of channels, but aerosol transmission is absolutely dominant, such as tuberculosis, measles and varicella;

(2) Accidental airborne transmission refers to transmission mainly through other channels such as droplets, but aerosol transmission can occur under special conditions, especially when clinical tracheal intubation and other operations that can produce aerosols, such as influenza and infectious atypical pneumonia.

The second category is not usually classified as airborne transmission and is used in routine clinical care as a precaution against droplet transmission.

"Whether the current aerosol spread, especially widespread, needs to be further confirmed." Feng Lu Zhao said.


Previously, the content about the route of transmission of the virus in the "New Coronavirus Infected Pneumonia Diagnosis and Treatment Program (Trial Fifth Edition)" was also revised to "Transmission through respiratory droplets and contact is the main route of transmission, The route of transmission, such as aerosols and the digestive tract, remains to be clarified. ”。

On February 5, Li Xingwang, a member of the national medical expert group, explained at a press conference that aerosol transmission can be seen in respiratory infectious diseases, but for the new coronavirus, it is not clear whether there is aerosol transmission. In addition, although the virus has been detected in feces, there is no more evidence of intestinal transmission. The fine-tuning of the route of transmission proves that these phenomena are concerned, and the writing of the route of transmission may be changed in the future when evidence becomes available.
Does aerosol transmission have a big impact on us?
Pay attention, but don't panic.

The biggest characteristic of aerosol is:The particles are small and spread farther.The World Health Organization (WHO) report has pointed out that viruses or bacteria can spread over long distances through aerosols and cause widespread infections in a short period of time. The propagation distance of aerosols can reach tens of meters or even hundreds of meters, far exceeding the propagation distance of droplets.

Although it is easy to form, it is not easy to infect people, and we still have measures to prevent it.

Professor Li Houqiang of Sichuan University wrote an article saying that because the general aerosol particles are relatively large, Usually greater than 10 microns, 50 microns or more, the general medical mask can be blocked.

Particularly small aerosol particles (radius less than 0.1 microns), light weight, mainly distributed at high altitude (close to the ground from the soil), they will drift away with the wind, the possibility of being breathed. In addition, the aerosol particle than the surface energy is very large, but also charge, the virus is easily destroyed, the survival rate is not high.

For ordinary people who are not medical personnel, in real life, only when the threshold of a very high order of magnitude is reached can some viruses enter the human body from the mucosa.

Only a tiny proportion of viruses that hover over clothing and skin in the form of aerosols can enter the eyes, mouth and nose through the touch of the hand.This amount of virus, the possibility of causing disease is not high.


Will the aerosol from upstairs float into my house?

Many people worry: aerosol spread so far, can I still open the window for ventilation? Will the aerosol upstairs float into my house?



For the general community residents, can open the window ventilation.


To reduce the effects of suspended aerosols, proper ventilation measures are necessary. For example, in the construction of medical facilities, often use the way to replace the polluted air in the room.


However, it should be noted that aerosols may flow with the air. Due to improper airflow direction, contaminated aerosols can flow to clean areas.


If there are isolated people at home, they must be isolated in a single room or in a place where the whole house is out of air. When the public area or other rooms are naturally vented, the doors and windows of the house where the patient is located must be closed.


At the same time, be careful not to use high-flow equipment such as fans to ventilate, so as not to cause turbulence and resuspend the particles that have settled.
How to prevent aerosol transmission?

On this point, there are seven suggestions worth adopting to prevent the "seven needs":


First, cancel all personnel gathering activities.To discourage friends and relatives from key epidemic areas from visiting;


Second, open windows often and ventilate more.Maintain indoor air circulation;


Three to do a good job in daily home disinfection: Wipe and disinfect key parts such as door handles, tables and chairs, toilet cushions with 75% alcohol or chlorine-containing disinfectant;


Four to talk about personal hygieneWash your hands with running water, soap or hand sanitizer before and after meals, and cover your mouth and nose with a tissue or elbow bend when coughing or sneezing;


Five to avoid air and contact transmission: Family members should avoid contact with the body secretions of people with suspicious symptoms, and do not share personal daily necessities; When eating, share meals with public chopsticks, eat quickly, talk less, communicate with each other should not be close, avoid shaking hands and hugs, and speak etiquette with a smile;


Six to strictly do a good job of home isolation: Foreign personnel should cooperate with relevant investigations, accurately report the facts, and take the initiative to accept isolation; If you need home isolation and observation, you should try your best to live in separate houses with your family. If conditions are limited, you should live in separate rooms and be isolated in single rooms. All family members living in the same house should wear masks;


7. Pay close attention to the health of family membersIn case of fever, cough and other symptoms, you should consciously avoid contact with others, go to the nearest fever clinic as soon as possible after wearing a mask, and fully cooperate with the treatment.






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