Aerosol transmission is reported in many places leading to infection! How to prevent it?

On April 12, Taierzhuang District, Zaozhuang City, Shandong Province, issued an emergency reminder that a resident of the district who did not wear a mask went outdoors to dig wild vegetables and was infected by an asymptomatic infected person who did not wear a mask while staying there at the same time. After epidemiological investigation and analysis, it is determined that aerosol transmission leads to infection.

On the evening of April 10, the Ningbo Municipal Center for Disease Control and Prevention in Zhejiang Province issued a message informing a local confirmed case that a local confirmed case entered an underground parking lot in a private car (driving window and not wearing a mask), and that 2 other recurrent cases stayed in the parking lot and did not wear a mask during the same time period, and there was a possibility of infection caused by aerosol transmission.

China News Service reporter Yin Liqin photographed

According to the diagnosis and treatment plan for novel coronavirus pneumonia released on March 14 (trial version 9), there are three ways of transmission of the new crown virus:

Transmission through respiratory droplets and close contact is the main route of transmission;

Aerosol propagation in a relatively closed environment;

Infection can also occur when exposed to an item contaminated with the virus.

Compared with other transmission routes, aerosol transmission seems to be more "erratic", which has a lot to do with the characteristics of aerosols.

What is aerosol transmission?

First of all, we need to clarify a concept: what is an aerosol?

"Aerosol refers to a system of solid or liquid particles suspended in a gaseous medium and composed of tiny particles between 0.001 and 100 microns in diameter."

Chen Chunqi, a professor at the School of Life Sciences of Hubei University, explained that just like the smoke produced by smoking, it is suspended in the air for a long time, and sometimes even if you can't see it, you can smell the smell of smoke.

The new coronavirus, which is about 0.1 microns in diameter, can attach to dust, droplets, or droplet nuclei that have lost moisture, and "airborne" in the form of aerosols, which is aerosol transmission.

"Heavy droplets and dust quickly fall to the ground, while small mass droplet nuclei hardly sink in the air. Moreover, the coronavirus in the droplet nucleus is protected by a protein membrane shell that can remain active for a considerable period of time. As a result, aerosols can float farther away, causing long-distance propagation. Chen Chunqi said that this is also one of the reasons why aerosol transmission is relatively hidden.

How are aerosols produced?

How powerful is it?

Many behaviors can produce aerosols, such as breathing, coughing, talking, spitting, vomiting, urinating and defecating (water flushing), etc. Medical examiners and other personnel can produce aerosols when they come into contact with samples of patients' blood, urine, feces, etc. Due to the many ways in which aerosols are produced, the spread of viruses through aerosols also increases the uncertainty and occultity.

However, Chen Chunqi said that although aerosol transmission makes it more difficult for people to prevent, it is not invincible. "Normal breathing, while it can produce an aerosol, is much smaller than the amount produced by coughing and sneezing. In general, the CT value of the new crown virus in asymptomatic infected people with new crown virus is relatively high, and the viral load in the resulting aerosol will be relatively low, so the transmission force is also poor. ”

How can aerosol transmission be prevented?

Generally speaking, only when a very high threshold is reached, some viruses can enter the human body from the mucous membrane. Like in confined spaces or places with poor air circulation conditions, the risk of aerosol transmission of the virus is higher.

Q1

How can aerosol transmission be effectively prevented?

A

The Ningbo case occurred in the parking lot, which is a relatively closed space and the ventilation environment is not good. Aerosols are more afraid of air circulation, and as soon as the wind blows, the aerosols can quickly disperse. Therefore, frequent ventilation in the room is one of the ways to effectively prevent the spread of aerosols.

Q2

Do you still worry about aerosol transmission outdoors?

A

Outdoors can not "sit back and relax", Shandong cases occur outdoors. If there is no wind outdoors, the viral load in the aerosol can also reach a certain concentration.

At the same time, it is not excluded that some people are more susceptible to the virus, or like the Omiljung variant, because of its stronger ability to attach spike proteins to human cells, trace viruses may cause infection with the new crown virus.

"These two cases also remind us once again that in public places, whether indoor or outdoor, we must wear masks in a standardized manner, especially in closed and narrow spaces such as elevators, taxis, and offices."

Chen Chunqi reminded, "Masks can physically isolate aerosols with large particle diameters, and if they are masks with meltblown layers, they can adsorb small molecule aerosols through electrostatic action." ”

Q3

Will the aerosols in the air stop on clothes and skin, causing infection?

A

Only a tiny proportion of viruses that hover over clothing and skin in the form of aerosols can enter the eyes, nose, and mouth through the touch of the hand. Such a viral volume, the probability of causing the disease is not high.

Q4

In daily life, what should be paid attention to to prevent aerosol transmission?

A

Chen Chunqi suggested that every day, try not to go to crowded places, keep a certain distance from others, and generally use 2 meters as a safety distance for prevention. Wash your hands and disinfect frequently.

For the prevention of aerosol transmission by the sewer route, try to use the toilet when using the toilet, close the lid and flush the water.

The virus is cunning and must not be careless;

Do a good job of protection, wait for the epidemic to disperse!

Source: China Youth Network, Xinhua Net, Jimu News, etc