Infectious disease disinfection is the use of physical or chemical methods to destroy pathogens staying on different transmission media, thereby cutting off transmission routes and preventing and controlling the occurrence of infection. Its purposes:

Beyond this, many additional factors must be considered in practical engineering applications.

Kill all bacterial propagules including mycobacteria, viruses, fungi and their spores, and the vast majority of bacterial spores [3]. Common methods to achieve high-level disinfection include the use of chlorine-containing preparations, chlorine dioxide, ortho-phthalaldehyde, peracetic acid, hydrogen peroxide, ozone, tincture of iodine, etc., as well as chemical disinfectants that can achieve sterilization effect under specified conditions with appropriate concentration and effective action time for disinfection.

Kill various pathogenic microorganisms including mycobacteria except bacterial spores [3]. Common methods to achieve intermediate-level disinfection include the use of iodine disinfectants (povidone-iodine, chlorhexidine iodine, etc.), alcohol and chlorhexidine iodine compounds, alcohol and quaternary ammonium compound combinations, phenols and other disinfectants, under specified conditions with appropriate concentration and effective action time for disinfection.

Chemical disinfection methods that can kill bacterial propagules (except mycobacteria) and lipophilic viruses, as well as mechanical sterilization methods such as ventilation and rinsing. Such as the use of quaternary ammonium disinfectants (benzalkonium bromide, etc.), biguanide disinfectants (chlorhexidine), etc., under specified conditions with appropriate concentration and effective action time for disinfection.

Different infectious disease pathogens have their own characteristics and different tolerance to different disinfection methods. For example, bacterial spores have the strongest tolerance to various disinfection measures and must be treated with a strongly bactericidal sterilant, heat or radiation to achieve good results, so they are generally regarded as the representative of the most difficult to disinfect. Others, such as tuberculosis bacteria, are sensitive to heat disinfection but more tolerant to general disinfectants than other bacteria. Fungal spores are highly resistant to ultraviolet light but more easily killed by ionizing radiation. Enteric viruses have similar tolerance to peracetic acid as bacterial propagules, but quaternary ammonium salts are ineffective against them. Botulinum toxin is easily destroyed by alkali but highly tolerant to acid. As for other bacterial propagules and viruses, spirochetes, mycoplasma, chlamydia and rickettsia, all have poor tolerance to general disinfection treatment. Common disinfection methods can generally achieve good results.

The same disinfection method often has different effects on items of different natures. For painted smooth walls, the sprayed liquid is difficult to stay on, so rinsing and wiping are appropriate. For rougher walls, where the liquid easily stays, spraying disinfection can be used. Epoxyethane fumigation has better effect on cloth and paper that easily absorb drugs, but for metal surfaces, the time must be extended. Coagulating-protein drugs are not suitable for disinfection of feces and sputum, because protein coagulation can protect pathogens. Although high-pressure steam has a good bactericidal effect, it is not suitable for fur, plastic and artificial fiber products. Epoxyethane fumigation of celluloid products, high-concentration peracetic acid or chlorine-containing disinfectants such as bleaching powder soaking textiles, lysol soaked latex gloves multiple times for a long time, can all cause damage. Toxic or foul-smelling disinfectants are not suitable for food and tableware.

Transmission opportunities differ under different conditions, with different requirements for epidemic prevention. During an infectious disease epidemic, in severely affected epidemic areas, drugs and equipment with good efficacy should be concentrated and applied. In less affected peripheral areas, simple disinfection methods can be used. In infectious disease hospitals or wards, where patients are concentrated, contamination is severe and disinfection volume is large, fixed equipment and efficient measures should be adopted; household disinfection belongs to clinical measures, with small workload, and simple measures and methods can be used. Drinking water should be boiled after purification; domestic water can be disinfected with chlorine after purification. For respiratory infectious diseases, spatial isolation, ventilation and reasonable mask wearing should be emphasized; for gastrointestinal diseases, emphasis should be placed on disinfection of utensils, feces, vomitus and hand washing after contact. Disinfection of different diseases should be treated differently. Patients with viral hepatitis should be disinfected with stronger chlorine-containing disinfectants or chlorine agents, and general disinfectants such as quaternary ammonium salts and lysol should not be used.

There are physical, chemical and biological methods, but the biological method uses biological factors to remove pathogens, acts slowly and is not thorough in sterilization, so it is generally not used for disinfection of infected epidemic sources; thus disinfection mainly applies physical and chemical methods.

In addition, from an industrial development perspective, market demand is also driving technological progress.

3. Radiation disinfection has two types: non-ionizing and ionizing radiation. The former includes ultraviolet, infrared and microwave; the latter includes high-energy electron beams (cathode rays) of gamma rays. Infrared and microwave mainly rely on heat production to kill bacteria. Ionizing radiation equipment is expensive and causes certain harm to items and the human body, so it is used less. The most widely used is ultraviolet, which can cause changes in cellular components, especially nucleic acids, protoplasmic proteins and acids, leading to microbial death. The ultraviolet wavelength range is 2100-3280 A; the wavelength for killing microorganisms is 2000-3000 A, with the strongest effect at 2500-2650 A. Fungi spores have the strongest tolerance to ultraviolet, followed by bacterial spores, and bacterial propagules are the weakest, with few exceptions. Ultraviolet has poor penetration; those below 3000 A cannot pass through ordinary glass 2 mm thick. Dust in the air and relative humidity can reduce its bactericidal effect. Its penetration into water decreases with depth and turbidity. But because of its convenience and no damage to drugs, it is widely used for air and general surface disinfection. Exposure to ultraviolet can cause skin erythema, ultraviolet ophthalmia and ozone poisoning in humans, so people should avoid it or take corresponding protective measures when using it.

Sun exposure also relies on the ultraviolet in it, but due to scattering and absorption by the atmosphere, only 39% reaches the ground, so it is only suitable for microorganisms with low endurance and requires longer exposure.

On this basis, industry experts have also conducted extensive research and improvements.

Lysol (creosol soap solution): prepared from 47.5% cresol and potassium soap. Reddish-brown, easily soluble in water, has a decontamination effect, and its bactericidal power is 2-5 times stronger than carbolic acid. Commonly used as a 2-5% aqueous solution, it can be used for spraying, wiping, soaking containers and hand washing. Bacterial vegetative forms can be killed in 10-15 minutes; it has a poorer effect on spores.

(2) Acids kill both bacterial propagules and spores. But they easily damage items, so they are generally not used for room disinfection. 5% hydrochloric acid can disinfect and wash tableware and fruit; adding 15% salt to a 2.5% solution can disinfect fur and leather; 10 l/kg heated at 30 deg C for 40 hours. Lactic acid is commonly used for air disinfection; 10 g of lactic acid fumigated for 30 minutes in a 100 m3 space can kill staphylococci and influenza viruses.

(3) Alcohols. Ethanol (alcohol) at 75% concentration can rapidly kill bacterial vegetative forms, acts more slowly on general viruses, has uncertain effect on hepatitis viruses, has a certain killing effect on fungal spores, and has no effect on spores. Used for skin disinfection and thermometer soaking disinfection. Because it cannot kill spores, it cannot be used for surgical instrument soaking disinfection. Isopropyl alcohol has greater bactericidal ability against bacteria than ethanol, can cause anesthesia when absorbed through the lungs, but does no harm to the skin and can replace ethanol.

In addition, this technology has been widely applied and practiced in related fields.

(2) Lime (CaO) generates high temperature and dissolves protein on contact with water, killing pathogens. Commonly, 10-20% lime milk is used to disinfect excreta, with an amount twice that of the excreta, stirred and acted on for 4-5 hours. 20% lime milk is used to disinfect anthrax-contaminated sites, sprayed once every 4-6 hours, continuously 2-3 times. Brushing the wall twice can kill tubercle spore bacilli. Because of its unstable nature, it should be freshly prepared when used.

(1) Bleaching powder is the most widely used. The main component is calcium hypochlorite [Ca(ClO)2], containing 25-30% available chlorine, unstable, and can be decomposed by light, heat, moisture and CO2. Therefore it should be sealed and stored in a dark, dry place for no more than one year. The active ingredient hypochlorous acid can penetrate into cells, oxidize the sulfur-hydrogen genes of cell enzymes, and destroy cytoplasmic metabolism. It has strong and rapid bactericidal power in acidic environments; at high concentration it can kill spores; in powder form it is used for disinfection of feces, sputum, pus, etc. Add 200 g of powder per litre, stir well, and leave for 1-2 hours; for urine add 5 g per litre and leave for 10 minutes. 10-20% emulsion, in addition to disinfecting excreta and secretions, can be used to spray toilets, contaminated vehicles, etc. If stored for a long time, the actual available chlorine content should be measured and the preparation dosage corrected. Bleaching powder concentrate powder and tablets can contain up to 60-70% available chlorine, and can be reduced proportionally when used.

(2) Chloramine-T is an organic chlorine disinfectant containing 24-26% available chlorine, relatively stable, and loses only 0.1% available chlorine when sealed for one year. Slightly soluble in water (12%), with less irritation and corrosiveness, and acts more slowly than hypochlorous acid. A 0.2% solution for 1 hour can kill bacterial vegetative forms; a 5% solution for 2 hours can kill tubercle bacilli; killing spores requires more than 10 hours. Various ammonium salts can promote its bactericidal action. A 1-2.5% solution also acts on hepatitis viruses. The active liquid must be prepared 1-2 hours before use, and its bactericidal action decreases if left too long.

(3) Sodium dichloroisocyanurate, also known as Youlujing, is a widely used organic chlorine disinfectant containing 60-64.5% chlorine. It has the advantages of high efficiency, broad spectrum, stability, high solubility and low toxicity. The aqueous solution can be used for spraying, soaking and wiping, and the powder can also be used to directly disinfect pollutants, treat feces and other excreta, with usage the same as bleaching powder. Direct spraying on the ground, dose 10-20 g/m2. Mixed and ignited with polyoxymethylene powder, the gas can be used for fumigation disinfection; it can be mixed with No. 92 coagulant (based on hydroxyaluminum chloride, synthesized with iron powder, sulfuric acid, hydrogen peroxide, etc.) at 1:4 to form Yushuiqing for drinking water disinfection. It can also be formulated with sodium sulfonate into various disinfection washing liquids such as Dijingmei and Youlujing. It has a killing effect on hepatitis viruses.

(4) Peracetic acid, also known as peroxyacetic acid, is a colorless transparent liquid, volatile with a pungent acidic smell, is a high-efficiency rapid disinfectant, easily soluble in water and ethanol and other organic solvents, has bleaching and corrosive effects, is unstable, and easily decomposes when encountering heat, organic matter, heavy metal ions and strong alkalis. At 0.01-0.5%, 0.5-10 minutes can kill bacterial vegetative forms; a 1% solution for 5 minutes can kill spores; commonly used concentration is 0.5-2%, and disinfection can be carried out by soaking, spraying, wiping and other methods. Under sealed conditions, aerosol (5% concentration, 2.5 ml/m2) and fumigation (0.75-1.0 g/m3) disinfection can be performed.

It is worth noting that technologies and standards in this field continue to evolve and improve.

4. Cationic surfactants mainly include quaternary ammonium salts, which coagulate protein at high concentration and inhibit bacterial metabolism at low concentration. They have the advantages of bactericidal concentration, low toxicity and irritation, no bleaching or corrosive effect, no odor, stability and good water solubility. But their bactericidal power is not strong, especially poor against spores, greatly affected by organic matter, and have many incompatibility taboos, which are their shortcomings. Domestically produced ones include Xinjie'ermie, Xiaoduning (Dumicang) and Xiaodujing, of which Xiaoduning has stronger bactericidal power, with a common concentration of 0.5-1.0 per mille, which can be used for disinfection of skin, metal instruments and tableware. It is not suitable for disinfection of excreta and secretions.

(1) Formalin is a 34-40% formaldehyde solution with strong bactericidal action. A 1-3% solution can kill bacterial vegetative forms; a 5% solution for 90 minutes can kill spores; indoor fumigation disinfection generally uses 20 ml/m3 plus an equal amount of water for 10 hours; to eliminate spore contamination, 80 ml/m3 for 24 hours is required, suitable for fur, artificial fiber, silk and other heat-intolerant items. Because of its poor penetration and strong irritation, the items to be disinfected should be spread out and the room must be sealed.

(2) Glutaraldehyde acts like formaldehyde. It is relatively stable in acidic solution but has poor bactericidal effect; in alkaline solution it can be maintained for 2 weeks, but to strongly improve the bactericidal effect, usually 0.3% sodium bicarbonate is added to 2% glutaraldehyde to correct the pH value, enhancing the bactericidal effect and maintaining stability for 18 months. It is non-corrosive, with the advantages of broad spectrum, rapid action, high heat and low toxicity, and can be widely used for killing bacteria, spores and virus disinfection. It is not suitable for skin and mucous membrane disinfection.

(3) Epoxyethane is a colorless liquid at low temperature, with a boiling point of 10.8 deg C, so it is a gaseous sterilant at room temperature. Its action is to alkylate and destroy the protein metabolism of microorganisms. The general application is at 15 deg C, 0.4-0.7 kg/m2, for 12-48 hours. Each 10 deg C increase in temperature doubles the bactericidal power; relative humidity of 30% gives the best sterilization effect. It has the advantages of high activity, strong penetration, no damage to items, and no residual toxicity, and can be used for disinfection of paper, books, cloth, fur, plastic, artificial fiber and metal products. Because of its strong penetration, disinfection must be carried out in a sealed container. Avoid open flame to prevent explosion. Ventilate after disinfection to prevent inhalation.

(1) Iodine interferes with protein metabolism through halogenation, acts rapidly and persistently, is non-toxic, and is little affected by organic matter. Common ones are iodine tincture and povidone-iodine (iodine combined with surfactants as an amorphous complex). Commonly used for skin and mucous membrane disinfection, and emergency treatment of medical devices.

Beyond this, many additional factors must be considered in practical engineering applications.

Disinfection of drinking water. Chlorine dioxide is a very effective water purification agent for purifying drinking water, including good deodorization and decolorization ability, and high-efficiency sterilization and virus killing ability at low concentration. When chlorine dioxide is used for water disinfection at a concentration of 0.5-1 mg/L, it can kill 99% of bacteria in water within 1 minute. Its sterilization effect is 10 times that of chlorine gas and 2 times that of sodium hypochlorite; its ability to inhibit viruses is also 3 times higher than chlorine and 1.9 times higher than ozone. Chlorine dioxide also has the characteristics of rapid sterilization, wide pH range (6-10), no influence from water hardness and salt content, and can maintain a long-lasting bactericidal effect. It can efficiently eliminate protozoa, spores, molds, algae and biofilm, and does not generate chlorophenols and trihalomethanes, and can oxidize many organic compounds, thereby reducing the toxicity and mutagenicity of water.

At the same time, the associated supporting processes and equipment are also being continuously optimized and upgraded.

In the medical field, chlorine dioxide is used for oral rinsing, which can effectively control gingivitis, dental plaque and halitosis; used as a sitz bath or rinse, it can prevent various diseases, etc. In the 1998 flood relief, flood-fighting soldiers used chlorine dioxide disinfectant to wash their faces, sitz bath, wipe their bodies, soak their feet and wash their underwear, and its magical effect was verified again. Practice has proved that chlorine dioxide has a good effect on preventing and treating red eye disease, skin diseases and deodorization.

On this basis, industry experts have also conducted extensive research and improvements.

(1) Toilets, toilet bowls and garbage can be sprayed and disinfected with 3% bleaching powder or 2% sodium chlorate supernatant, and the utensils should be soaked for 1 hour; the patient's vomit and excreta should be fully mixed with 1%-20% double the amount of bleaching powder and placed for 2 hours.

Beyond this, many additional factors must be considered in practical engineering applications.

Hepatitis B virus disinfection method three: it is best to discard garbage and waste. Hands that have touched contaminants should first be soaked in 0.2% peracetic acid for 2 minutes, then washed clean with soap and running water.

On this basis, industry experts have also conducted extensive research and improvements.

Acid-alkali disinfectants on the market include nitric acid, sodium hydroxide, quicklime, etc. They are widely used in the food processing industry. They are generally used as pipeline sanitation cleaning and pre-disinfection.

These disinfectants are all high-efficiency, broad-spectrum sterilants, safe, fast, with good sterilization effect and no residue, convenient to use, but individual products are unstable, easily decomposed, have high use cost and have odor, etc. The main products on the market are chlorine dioxide, peracetic acid, hydrogen peroxide, etc. They are mainly applied to the disinfection and sterilization of equipment, pipelines, utensils, air, food, hands and other fields.

In 2013, the main aldehyde disinfectants on the market were formaldehyde, glutaraldehyde, epoxyethane, etc. Until 2013, they were mainly used for disinfection of instrument surfaces and air in the medical industry, and this type of disinfectant cannot be used for disinfection in the food field.

The advantages of alcohol disinfectants are convenient, safe, fast and volatile use, and the disadvantage is high use cost. The main products are ethanol, isopropyl alcohol, etc., mainly applied to the disinfection of process utensils, instruments and hands in food processing and medical industries.

On this basis, industry experts have also conducted extensive research and improvements.

6. Add commonly used disinfectants to detergents. [2]