On February 8, the Shanghai Municipal Government held a press conference on epidemic prevention and control. At the press conference, health and epidemic prevention experts confirmed that the transmission routes of pneumonia of new coronavirus infection that can be identified are mainly direct transmission, aerosol transmission and contact transmission.
Researcher at the Institute of Geoenvironmental Sciences, Chinese Academy of Sciences, Director of the Chinese Academy of Sciences Aerosol Chemistry and Physics Key Laboratory, and Secretary-General of the International Aerosol Society, Cao Junxuan said in an interview with ScienceNet that aerosols are fluids that are discharged during daily talking, laughing, singing, etc. Drops, breathing, coughing, sneezing and size all produce droplets. Its particle size is generally 0.1 mm or less. It evaporates quickly after exhaling the human body (within 1 second or even tens of milliseconds) to form a droplet core (particle diameter of several microns). The droplet core is suspended in the air for a long time and migrates with the air. Its transmission distance can reach hundreds of meters or even longer, increasing the risk of contactless transmission.
Earlier, on February 5, the Health and Medical Commission issued the "Diagnosis and Treatment of New Coronavirus Infected Pneumonia (Trial Fifth Edition)", regarding the transmission route in the previous "Respiratory droplet transmission and contact transmission is the main route "Based on the addition of" aerosol and digestive tract transmission channels to be determined. "
At the press conference of the State Council's Joint Prevention and Control Mechanism on February 5, a reporter asked why the above statement was added. Li Xingwang, member of the National Medical Expert Group and chief expert of the Infectious Diseases Diagnosis and Research Center of Beijing Ditan Hospital, said that the spread of aerosols can be seen in respiratory infectious diseases, but there is no aerosol transmission of the new coronavirus. At present, Is ambiguous.
"Is there a virus detected in the feces, will there be such a route of intestinal transmission? There is no more evidence. So the diagnosis and treatment plan says 'transmission routes such as aerosol and digestive tract are currently unclear.'" Li Xingwang said. The description of the fifth edition of the diagnosis and treatment plan for the transmission route is also based on the clinical characteristics and occurrence and development characteristics of the disease, and the experience is incorporated into the plan in time to guide the clinical practice.
The term "aerosol" frequently appears before the general public after the outbreak of new coronary pneumonia.
On January 21, Professor Wang Guangfa, a member of the National Health and Medical Commission's Wuhan expert group and director of the Department of Respiratory and Critical Care Medicine, Beijing First Hospital, confirmed the diagnosis of new coronary pneumonia. After recovering, Wang Guangfa analyzed his own pathogenesis and stated that the earliest symptom after returning to Beijing was conjunctivitis of the left lower eyelid. Therefore, he suspected that the virus entered the conjunctiva first and then went to the whole body.
Although there has been no clear indication of the process of Professor Wang Guangfa's infection, there have been vocal speculations that conjunctival infection may be a form of droplet or aerosol transmission.
Recently, there have also been a number of cases of infection that caused concern. Among them, an infected person who did not wear a mask in Ningbo City was only 15 seconds away from a confirmed patient who did not wear a mask to be infected.
Many viruses such as SARS and H5N1 were thought to be able to spread through air or aerosols.
In 2003, 321 people were infected with SARS virus in Block E of Amoy Gardens in Hong Kong, killing 42 people. Because the risk of infection of middle and high-level residents is higher than that of bottom-level residents, random transmission is not applicable. It is considered that feces containing SARS virus are most likely to pass sewage. Aerosol propagation through pipes.
That being the case, are we going to be particularly nervous or even panic?
Professor Li Houqiang, a professor at the School of Social Sciences of Sichuan University, wrote that because aerosol particles are relatively large, generally larger than 10 microns, and the most above 50 microns, general medical masks (or masks to prevent smog) can block such particles. Particularly small aerosol particles (with a radius of less than 0.1 micron) and light weight are mainly distributed at high altitudes (from the soil near the ground). They drift away with the wind and are less likely to be breathed by people. In addition, the aerosol particle has a large specific surface energy and has an electric charge. The virus is easily destroyed and the survival rate is not high.
For non-medical personnel, in real life, only when the threshold of an extremely high order is reached can some viruses enter the body from the mucosa. Similarly, only a very small percentage of viruses that hover on clothing and skin through aerosols can enter the eyes, mouth, and nose through the touch of the hands, and the possibility that the amount of virus can cause disease is not high.
In response to the current transmission channels, Zeng Qun, deputy director of the Shanghai Municipal Civil Affairs Bureau, called on residents to achieve "seven requirements" for home epidemic prevention:
First, we must cancel all social gatherings and discourage relatives and friends in key epidemic areas from postponing visits;
Second, windows must be opened frequently, and more ventilation should be provided to maintain indoor air circulation;
Third, do daily household disinfection: wipe key points such as door handles, tables, chairs, and toilet seats with 75% ethanol or chlorine-containing disinfectant;
Fourth, talk about personal hygiene: wash your hands with running water, soap or hand sanitizer before and after meals. Cover your mouth and nose with a tissue or elbow flexion when coughing or sneezing;
Fifth, avoid air and contact transmission: family members should avoid contact with body secretions of people with suspicious symptoms, and do not share personal daily necessities; during meals, divide chopsticks with food, eat fast, talk less, not communicate with each other, avoid shaking hands and hugging, arching Smile etiquette
Sixth, we must strictly isolate the home: field personnel must cooperate with relevant departments to investigate, accurately report the facts, and actively accept the quarantine; those who need home isolation and observation should try their best to live with their families in separate places. If conditions are limited, they should live in separate rooms and separate rooms. , All family members living in the same house must wear masks;
Seventh, pay close attention to the health status of family members, such as fever, cough and other symptoms, should consciously avoid contact with others, wear a mask, go to the nearest fever clinic as soon as possible, and fully cooperate with treatment.