The prevention and control of respiratory infectious diseases face great challenges, and both traditional and emerging respiratory infectious diseases pose serious risks to human health and even threaten human lives. According to the WHO, the annual number of influenza cases worldwide can reach 1 billion, including 3 to 5 million severe cases, and the number of deaths from influenza-related respiratory diseases can reach 290,000 to 650,000. In recent years, new respiratory infectious diseases have emerged, such as SARS in 2003, H1N1 in 2009, MERS in 2012, and COVID-19 in 2019. Transmission via respiratory droplets is the main transmission route of respiratory infectious diseases, and UV air purifier and proper disinfection are essential to prevent and control the spread of respiratory infectious diseases. This article provides a reference for healthcare institutions by sorting out the importance of air disinfection and common disinfection methods when preventing and controlling respiratory infectious diseases.
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1 The importance of the UV air purifier for the prevention and control of respiratory infectious diseases
1)Transmission characteristics of respiratory infectious diseases
Respiratory infectious diseases are respiratory diseases in which pathogens enter the body through the patient’s respiratory tract, such as the throat, nasal cavity, trachea, or bronchi, resulting in a series of respiratory diseases with infectious characteristics. Common traditional respiratory infectious diseases (e.g., influenza) and emerging respiratory infectious diseases (e.g., COVID-19, SARS, MERS, etc. ) are mainly transmitted via respiratory droplets and contact, and there is also the possibility of aerosol transmission, which has the characteristics of It is easy to cause outbreaks and epidemics, and is difficult to prevent and control.
2) The role of air in the transmission of respiratory infectious diseases
The air and aerosols and droplet particles in the air are important vectors for the transmission of respiratory infectious diseases. Some scholars in China have conducted a study on airborne transmission of respiratory infectious diseases, aerosols, and droplets. In China, scholars have conducted model predictions of the probability of infection for airborne and aerosol transmission of respiratory infectious diseases and found that the risk of cross-infection of respiratory infectious diseases is related to the risk of cross-infection. The risk of cross-infection of respiratory infectious diseases is related to the patient’s respiratory ventilation, patient’s The risk of cross-infection of respiratory infections was found to be related to the amount of respiratory ventilation of patients, the number of pathogens exhaled by patients, droplet size, number of patients, room ventilation and ventilation, exposure time, the distance between the exposed person and the patient, and the presence or absence of mask protection. Strengthening ventilation can dilute The airborne droplet nuclei exhaled by patients can be diluted, and the concentration of pathogens can be reduced by removing indoor air pollutants. This reduces the risk of cross-infection of respiratory infections.
The air around the area where patients with respiratory infections live may also be contaminated and increase the risk of cross-transmission of disease, which requires attention and focus. Smaller particles of microbial aerosols containing pathogens can be suspended in the air, and direct respiratory inhalation causes infection. A study by scholars in Taiwan, China showed that the occurrence of influenza cases was closely related to air quality. In the United Kingdom, air sampling and testing of areas where influenza A (H1N1) patients were found to be positive for influenza virus nucleic acid in air specimens. A study at the First Hospital of Jilin University also found that one out of 19 air specimens from isolation rooms of COVID-19 patients sampled before cleaning and disinfection were positive for COVID-19 virus nucleic acid. The NIH studied the stability of COVID-19 and SARS viruses in aerosols and on the surface of objects and found that the new coronavirus could survive in aerosols for 3 h. The State Key Laboratory of Virology, Wuhan University, sampled the air in the hospital area and toilets, residential areas, and supermarkets, and quantitatively analyzed the COVID-19 virus load and airflow dynamics characteristics, and found that the air in the isolated hospital area had a high aerosol deposited particle virus load, which could cause environmental pollution. During the SARS epidemic, some scholars studied the air pollution inside and outside the SARS ward of the designated hospital Xiaotangshan and found that SARS patients’ wards, inner corridors, nurses’ stations, and ward exhausts were positive for viral nucleic acid at 5 m downwind, but no live SARS virus was detected in all air specimens, considering that ventilation and disinfection measures in SARS patients’ wards can effectively reduce the degree of indoor pollution. Outbreak event, the number of infected people exceeded 300 cases, researchers established a flow dispersion model of SARS virus aerosol based on fluid dynamics, and the results showed that aerosol is an important route of SARS transmission in the district, and the spatial distribution of infected patients and other factors have an important impact on SARS transmission.
3) UV Air disinfection requirements for the prevention and control of respiratory infectious diseases
UV Air disinfection is an important means to cut off the transmission of respiratory infectious diseases and is one of the key aspects of controlling the spread of respiratory infectious diseases. In medical activities, The adoption of scientific and appropriate dynamic UV air purifier methods in the process can effectively control the occurrence of hospital infections and effectively control the occurrence of hospital infections and cross-transmission of various respiratory infectious diseases. The cross-transmission of various respiratory infectious diseases. According to the requirements of relevant national norms and standards, medical institutions with medical institutions should isolate patients with respiratory infectious diseases, especially airborne diseases, in the building layout. patients with respiratory infectious diseases, especially airborne diseases, should be isolated in a negative pressure ward that meets the requirements of building layout and air management. The negative-pressure ward should meet the requirements of building layout and air management. However, during epidemic outbreaks of respiratory infectious diseases, Most of the isolation wards for patients with respiratory infectious diseases do not have strict, However, during an epidemic of respiratory infectious diseases, most isolation wards patients with respiratory infectious diseases do not have strict negative pressure isolation. Infectious disease departments/fever clinics, emergency clinics, and respiratory clinics are also respiratory clinics. Infectious disease/fever clinics, emergency departments, and respiratory clinics are also high-risk areas for the spread of respiratory infectious diseases. The importance of air management and proper disinfection is particularly important. Influenza prevention and control The importance of air management and proper disinfection is particularly important. The importance and requirements of air disinfection have been clearly stated in the COVID-19 prevention and control program. The importance and requirements of UV air disinfection have been clearly pointed out.
According to the requirements of the national guidelines, and taking into account the results of relevant domestic and foreign literature, the common methods of UV air purifier for the prevention and control of respiratory infectious diseases, including the scope of application of physical and chemical disinfection, the methods of use and their effects, are briefly introduced.
2 Disinfection method
1) Physical disinfection
➀ Ventilation includes natural ventilation and mechanical ventilation.
Natural ventilation refers to the ventilation exchange by using the thermal or wind pressure caused by the difference in density of the air inside and outside the building to promote airflow. Researchers have studied the effect of natural ventilation on the spread of respiratory infectious diseases inwards by using field measurements, numerical simulations, and theoretical calculations, and the results showed that appropriate natural ventilation can meet the minimum limits of the relevant standards forward ventilation and maintain the risk of infection inwards at a level comparable to that of mechanical ventilation, which can be an effective means of preventing and controlling the spread of respiratory infectious diseases. Natural ventilation has been shown to be the simplest, effective, and sustainably applied form of UV air purifier for the prevention and control of pathogen transmission and can significantly reduce the spread of influenza. In areas with good ventilation and clean outside air, natural ventilation can be applied at appropriate times. The COVID-19 prevention and control program issued by the National Health and Wellness Commission also recommends that air circulation be maintained in patient isolation rooms, with ventilation two to three times a day for at least 30 min each time. mechanical ventilation refers to airflow by installing ventilation equipment and using the power generated by the operation of fans and exhaust fans. Infectious disease hospital building design specifications proposed infectious disease hospitals or infectious disease areas should be set up mechanical ventilation system, respiratory infectious disease clinics, fever clinics, the minimum number of air changes should be 6 times/h, to take the “up to send down” mode, follow the principle of clean dirt does not cross, do not reverse flow, different areas of air supply, exhaust air separate independent set up. Compared with natural ventilation, mechanical ventilation is not easily affected by environmental factors such as season, outdoor wind, and temperature, but there are problems in energy consumption, pipe design, fan power, and cleaning and disinfection of mechanical ventilation equipment. However, there are challenges in energy consumption, duct design, fan power, and cleaning and disinfection of mechanical ventilation equipment.
➁ Centralized air conditioning ventilation systems
Research related to the transmission of air conditioning ventilation system and respiratory infectious diseases: During the SARS epidemic in 2003, a hospital in Beijing conducted filter and condensate sampling tests on the air conditioning system in the SARS ward and found the presence of SARS virus; American scholars tested the filters of air conditioning ventilation system for common respiratory infectious viruses and found that some filters detected influenza and parainfluenza viruses. Nucleic acids were detected in some filters. At present, there is no clear evidence that the COVID-19 is transmitted through air conditioning, and scholars at home and abroad also have different views, but there are cases that show that not configured with a good filtration system, the unit constantly circulates indoor air can not reduce the number of indoor viruses, but rather disrupt the indoor airflow, making the locally generated germs spread to the whole room, increasing the risk of transmission, so before starting the air conditioning ventilation system, it is necessary to grasp the system COVID-19, during the SARS epidemic in 2003, relevant guidelines were issued for the operation of air conditioning and ventilation systems in office and public places.
- All air conditioning ventilation systems should close the return air valve and operate in an all-fresh-air manner;
- Fan coil plus fresh air ventilation system should ensure that the fresh air is taken directly from the outdoors, prohibiting the taking of air from the machine room, building and ceiling, ensuring the normal operation of the exhaust system, and the normal operation of the large The room should take measures to ensure the ventilation of the internal area. The maximum fresh air volume is appropriate for the operation of the new air system, and the prevention and control of SARS in hospitals. The technical guidelines for the prevention and control of SARS hospital infection recommend that the fresh air volume should not be less than 30 m3 / person-h.
- For UV air conditioning or fan coil system without fresh air (similar to household split type air conditioning), the ventilation system should be opened or windows should be opened to enhance air circulation. The cleaning and disinfection of the air conditioning and ventilation system shall follow the “Regulations for Cleaning and Disinfection of Centralized Air Conditioning Systems in Public Places” (WS). Ventilation system cleaning and disinfection regulations” (WS/T396-2012). When confirmed or suspected cases of respiratory infectious diseases are found on the premises, the use of the system should be suspended. Suspend the use.
➂ Ultraviolet disinfection
Ultraviolet irradiation is effective in killing respiratory infectious disease viruses. The use of UV irradiation to test the suspensions of SARS, MERS, influenza A, Ebola and respiratory syncytial virus for 5 min was able to inactivate the above viruses. Previous studies have shown that external UV disinfection has a good effect in blocking the transmission of influenza. Foreign scholars used 200-280 nm wavelength UV irradiation of SARS virus to study the inactivation effect and found that the virus was partially inactivated after 1 min, and within 1-6 min, the longer the irradiation time the more significant the inactivation effect, and after 15 min irradiation inactivation to below the detection limit level Similar results were obtained in an Italian study on the effect of UV irradiation on coronavirus activity. The air purification management code suggests that the use of UV air disinfection should follow the manufacturer’s instructions, the average number of installed lamps is ≥1.5 W/m3, and the UV lamps are suspended or mobile direct irradiation with an irradiation time of ≥30 min. attention should be paid to keeping the surface of the UV lamps clean, wiped with 70% to 80% ethanol once a week, and wiped promptly when dust and oil are found on the surface. The room should be kept clean and dry during UV disinfection to reduce dust and water mist, and the irradiation time should be extended when the temperature is <20℃ or >40℃ and the relative humidity is >60%; the irradiation intensity of UV should be monitored regularly, and the irradiation intensity of the new UV lamp should not be less than 90μw/cm2, and the irradiation intensity of the UV light in use should not be less than 70μw/cm2 and should be changed in time when the irradiation intensity is reduced to the required value. Change. UV disinfection operation is simple and convenient, no pollution to the surrounding environment, but the disinfection effect is affected by the irradiation time and distance, ambient temperature and humidity, whether the lamp is clean, and other factors and direct irradiation of human eyes can cause electrophotographic ophthalmia, resulting in corneal damage, suitable for indoor air disinfection in an unoccupied state.
2) Chemical disinfection
Chemical disinfection is a method of preventing and controlling the spread of infectious diseases by applying chemical disinfectants that have a killing effect on pathogens and using tools to suspend them in the air to kill the pathogens. Common chemical disinfectants that are effective against respiratory pathogens include peracetic acid, chlorine dioxide, hydrogen peroxide, and ozone. Italian scholars studied the resistance of disinfectants for SARS and influenza viruses and found that 0.05% sodium hypochlorite and 0.035% peroxyacetic acid could inhibit the replication of the SARS virus for 2 min and completely destroy the genetic integrity of the virus for 30 min, while 0.1% sodium hypochlorite could completely destroy the replication of SARS virus and influenza A virus and their genetic integrity for only 1 min. 0.5% hydrogen peroxide and 0.1% sodium hypochlorite were effective in reducing the infectivity of SARS, MERS, and human coronavirus within 1 min. At a temperature of 20℃ and 70% humidity, 20.3 mg/m3 ozone was able to kill the airborne virus for 20 min. At a temperature of 20°C and a humidity of 70%, 20.3 mg/m3 of ozone was able to kill the airborne coronavirus for 20 min. Due to the chemical disinfectants being generally irritating and corrosive, they are suitable for indoor air disinfection under unoccupied conditions. indoor air disinfection under unoccupied conditions, they are mostly used in medical institutions for final disinfection after patients are discharged. The hospital air purification management standard recommends the use of ultra-low The hospital air purification management standard recommends the use of ultra-low volume spray and fumigation for air disinfection of chemical disinfectants.
➀ Ultra-low volume spraying method
The ultra-low volume spray method is to atomize the disinfectant into tiny particles below 20μm and spray evenly in the air so that the chemical disinfectant is in full contact with microbial particles in the air to kill microorganisms in the air: 3% hydrogen peroxide, 5000mg/L peroxyacetic acid or 500mg/L chlorine dioxide and other disinfectants will be configured and added to the ultra-low volume spray according to the dosage of 20-30mL/m3. sprayers. Close doors and windows, cover indoor corrosive instruments and equipment, such as monitors, displays, and other items, disinfection personnel to do a good job of personal protection, wear protective gloves, masks, antivirus masks if necessary, wear protective clothing; turn on the power for disinfection, according to first up, then down, first left, then right, from inside to outside, the first surface, then space, in a gradual order of uniform spraying; after the end of spraying personnel evacuation, close doors and windows, let disinfectants to give full play to the role of hydrogen peroxide, chlorine dioxide 30 ~ 60min, peroxyacetic acid for 1h; disinfection time up to open the doors and windows after thorough ventilation.
➁ Fumigation method
Fumigation is the use of chemical disinfectants with volatility in a certain space by heating or other methods to make it volatile. Close the windows and doors, and put the appropriate amount of 0.5% to 1.5% of the product into the air according to the instructions. The appropriate amount of 0.5%~1.0% (5000~10000mg/L) peroxyacetic acid aqueous solution (1g/m3) or chlorine dioxide 10-20mg/m3 into Corrosion-resistant, suitable size of the container, heating evaporation or adding activator. Or use 20mg/m3 ozone fumigation disinfection.Operation time, operation Follow the product instructions and open the windows and doors for thorough ventilation after disinfection. After disinfection, open doors, and windows for thorough ventilation.
3) Air Sterilizer
Air purifiers are used for indoor UV air disinfection in occupied conditions and are increasingly used in medical institutions. The basic principle of air disinfectors is that the air entering the air disinfector is effectively killed and dust particles are filtered out by the elimination factors in the air disinfector. Currently, common elimination factors for air disinfectors include filtration, circulating air UV, electrostatic adsorption type, photocatalytic oxidation, and other physical technologies and chemical technologies such as ozone. There are differences in the effectiveness of different elimination factors: researchers measured the effect of silver, copper, and their oxidants on SARS virus killing at room temperature, and the results showed that silver and copper catalytic oxidation acted for 5 and 20 min respectively SARS virus was completely inactivated, indicating that catalytic oxidation is a potential method for air disinfection through air disinfection systems. The effects of ultrafiltration bacteria removal and electrostatic adsorption are influenced by the structure, characteristic properties, filter level, and pore size of the filter material. The effect of UV light on respiratory infectious disease pathogens The effect of UV on respiratory infectious agents has been described previously, and the effect of chemical agents such as ozone The effects of chemical reagents such as ozone will be described later and will not be repeated here. However, how to ensure that the elimination factors of the air disinfection The elimination factor of the air disinfector can work continuously to achieve effective killing of pathogens. and the effect of different elimination factors on respiratory pathogens. The disinfection effect of air disinfectors on respiratory pathogens needs to be further studied. And air disinfectors should obtain the health department’s sanitary permit for disinfection products. The air disinfectors should obtain health approvals from the health department for disinfection products and follow the instructions for use of disinfection products when using, servicing, and maintaining them. The instructions for use, maintenance, and repair of disinfection products should be followed. Close doors and windows when disinfecting, and the circulating air volume (m3 /h) of the disinfector should be greater than The air volume (m3 /h) of the disinfector should be more than 8 times the volume of the indoor room, and the air inlet and outlet should not be covered or blocked by objects. When cleaning the machine with a wet cloth, cut off the power supply first.
Summary
UV Air disinfection can effectively prevent and control the spread of respiratory infectious diseases and avoid cross-infection. During the epidemic of respiratory infectious diseases, good indoor ventilation should be maintained, and the correct use of a centralized air conditioning ventilation system in the presence of natural ventilation, mechanical ventilation or air disinfection with air disinfectors can be used according to the actual situation. Air disinfection can be carried out with the UV air purifier. In the unoccupied state, the air can be disinfected by using purple ray irradiation, or by using appropriate concentrations of peroxyacetic acid, chlorine dioxide, hydrogen peroxide, etc. chlorine, hydrogen peroxide, and other chemical disinfectants, using ultra-low volume spray method or Fumigation method to disinfect the air.
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