How the virus spreads in the air

by LiuJie on September 20, 2022

      The physiological activities of the human body are closely related to the air, but aerosol transmission is also a common way of virus transmission. Many virulent viruses can be transmitted by aerosols. As the air enters the respiratory tract, the virus exchanges gas through the alveoli, and then enters the body, causing the body's working mechanism to be out of balance. In addition, the high density of urban residential areas has produced a breeding ground for infectious diseases that spread quickly, such as SARS in 2003 and COVID-19 in 2019. As a result, urban areas have grown larger and more populated, which has enhanced the speed and effectiveness of airborne viral transmission. The public health department therefore places a high emphasis on the airborne virus since it will have a significant public impact once a public health incident brought on by airborne transmission happens.


      Like all living things, viruses also have heredity, mutation, and evolution. They are very small in size and extremely simple in structure. However, viruses do not have a cellular structure and are mainly composed of internal nucleic acid and external protein shells. They cannot survive independently. They can only carry out life activities by parasitizing the living cells of other organisms. Once they leave the cells, they will become crystals. The genetic material and part of the protein of the virus are then transferred between different organisms through these crystals. There are many ways for this crystal to spread, such as through water, food, air, etc. But not all viruses can be transmitted through the air, only some specific viruses can be transmitted through the air, such as tuberculosis, influenza virus, etc., such viruses can be suspended in the air,  and can spread long distances in the air (>lm), and remain infectious for a long time. Therefore, these viruses are also called airborne viruses.


These illnesses also include those that are preferentially airborne, such as open tuberculosis, and infections that are airborne. The primary method of viral transmission and only one type of airborne transmission for respiratory illnesses. By entering the air and creating aerosols or virus nodules connected to airborne particles, this substance or procedure disperses the virus that is respiratoryly expelled from other organisms and attached to airborne particles. Through the respiration of other organisms, the virus that causes tuberculosis enters the body through the respiratory system. Once these viruses' crystals have entered the organism, they will utilise the material created by the host cell to finish the transcription and replication of their own genetic material, ultimately leading to the death of the organism's host cell. The SARS virus that broke out in 2003 is a virus that can be transmitted from person to person, and the COVID-19 virus that broke out in 2019 is a homologous virus of SARS, both of which are coronaviruses. Statistics show that the SARS outbreak in 2003 resulted in a total economic loss of 40 billion US dollars, of which 53,247 cases and 349 deaths occurred in mainland China, 1,755 cases and 300 deaths in Hong Kong, China; 665 cases and 180 deaths; 251 cases and 41 deaths in Canada; 38 cases and 33 deaths in Singapore; and 63 cases and 5 deaths in Vietnam.


      Droplet transmission is a way in which pathogens are detached from the source of infection, spread to the infectable host, and then enter the organism, resulting in biological infection. According to the distance of droplet transmission, it can be mainly divided into three ways: close-range droplet transmission, long-distance gas transmission and object surface transmission. Droplet Transrmss10n refers to the droplets containing the largest pathogens that enter the environment through the mouth and nose when the patient exhales, sneezes, and coughs. The large droplets quickly land on the ground, and the medium-diameter droplets stay in the air for a short time. , then fall around the source of infection. If the droplets leave the human body and there are people around who are talking, when breathing and coughing, these droplets will enter the lungs from the nasopharynx. Another part of the pathogen droplets is directly deposited on the eye membrane, nasal mucosa or mouth of susceptible people, causing biological infection. Close-range droplet transmission refers to the transmission range, which is essentially less than 1 m from the source of the pollution. Additionally, there are some sprayed droplets that, due to their small particle size, can float in the air for a considerable amount of time. This route of transmission is known as droplet nuclei transmission because when the droplets evaporate and become droplet nuclei, these droplet nuclei carrying viruses are inhaled or deposited on the mucous membranes by susceptible people, causing them to become infected. Because the genetic material in the droplet nucleus is difficult to fail, this type of transmission distance is long, reaching lengths of tens to hundreds of meters, and the range is broad.


      When the droplets in the air meet the particles in the air, the electrostatic adsorption between the particles makes the droplet nuclei in the air or the droplets just discharged from the human body adhere to the particles and suspend together with the particles in the air In the air, aerosols are formed. These particles are inhaled into the respiratory tract with the air and enter the human body. This spread is known as dust spread. Airborne transmission is shown in Figure. Wearing a face mask can effectively prevent the spread of droplets, not only to protect yourself but also to protect more people.


      The spread of different viruses requires different routes of transmission. Airborne viruses mainly include influenza virus, cold virus, coronavirus, bird flu virus, etc. However, the outbreak of this type of epidemic depends on a variety of conditions, among which population density, sanitary conditions, and the proportion of susceptible people in the population play a decisive role.


      Influenza viruses are highly contagious and spread in many ways. Ordinary people can get sick through direct or indirect contact with pollutants that carry the virus, or they can get sick through droplets or droplets that carry the virus. Some studies have shown that some influenza viruses can spread through the air. For example, some researchers used H3H2 virus to infect two groups of volunteers, and carried out influenza virus aerosol transmission experiments on the volunteers. The results of this experiment show that the virus can be transmitted from person to person through aerosol transmission. However, not all subtypes of influenza viruses have aerosol transmission capabilities, and different subtypes of influenza viruses that also have aerosol transmission capabilities have different transmission capabilities. Therefore, some subtypes of influenza viruses can be airborne. Several other types of viruses have been scientifically found that they can be transmitted through the air like influenza viruses, but the difference is their ability to spread and cause disease.