动物实验 z-bo 2020-09-14 411

　　In the early stages of the epidemic, the issue of whether to wear a mask was debated in the United States and Europe. The main route of transmission of the new coronavirus is still medium to large-sized respiratory droplets. The use of surgical masks can theoretically reduce respiratory droplets exposure. However, the use of surgical masks to prevent COVID-19 has yet to be supported by experimental evidence. In March of this year, Gao Fu, director of the China Centers for Disease Control and Prevention, bluntly stated in an exclusive interview with Science magazine that it was a big mistake not to wear masks in Europe and America. This still caused some controversy at the time.

　　The latest research puts an end to this controversy, and Gao Fu is right. The research team from China used animal experimental models to test:

　　Using surgical masks can reduce the probability of the spread of new coronavirus droplets, especially when the infected person wears a mask, the effect is especially obvious.

　　A joint research team from the Li Ka-shing School of Medicine, Department of Microbiology, State Key Laboratory of Emerging Infectious Diseases, University of Hong Kong Shenzhen Hospital, Department of Clinical Microbiology and Infection Control, Hong Kong Queen Mary Hospital, Department of Microbiology, etc. on May 30, local time In the international authoritative journal “Clinical Infectious Diseases” (Clinical Infectious Diseases), the title “Surgical mask partition reduces the risk of non-contact transmission of the new crown virus in the golden Syrian hamster model” (Surgical mask partition reduces the risk of non- contact transmission in a golden Syrian hamster model for Coronavirus Disease 2019 (COVID-19)). The corresponding author of the study is Yuan Guoyong, academician of the Chinese Academy of Engineering and Chair Professor of the Department of Microbiology, Li Ka Shing School of Medicine, University of Hong Kong.

　　The researchers used golden Syrian hamsters as a SARS-CoV-2 model. They placed the indicator hamsters and uninfected hamsters infected with the new coronavirus in a closed system unit. Each unit is composed of two different cages. Surgical mask materials are used between the cages. There is a one-way airflow inside the partitions to study the effect of the surgical masks placed between the cages. In addition to the clinical score, they also tested the viral load, histopathology, and viral nucleocapsid antigen expression of Kuramomoto.

　　66.7% (10/15) of the directly exposed pups without a surgical mask as a partition were infected. Isolate infected indicator hamsters (infected hamsters) or naive hamsters (uninfected hamsters) through surgical masks, and the transmission rate was significantly reduced to 25% (6/24, P=0.018). After zoning surgical masks specifically for indicator hamsters (hamsters that have been infected), the transmission rate was significantly reduced to 16.7% (2/12, P=0.019). It indicates that hamsters have more severe symptoms of new crown, and hamsters separated by surgical masks have lower clinical scores after infection, histopathological changes are mild, and viral nucleocapsid antigen expression in respiratory tissues is lower.

　　SARS-CoV-2 infection was initially thought to be an acute febrile pneumonia with lymphopenia and multifocal ground-glass shadows on chest CT. The new coronavirus infection is usually self-limiting, but it may also have serious clinical manifestations: such as no obvious symptoms at the beginning and then sudden failure; acute respiratory distress syndrome (ARDS); thrombocytopenia and diffuse microvascular thrombosis Intravascular coagulation; deep vein thrombosis due to pulmonary embolism; multiple organ failure, etc. The new crown infection may also cause gastrointestinal manifestations such as diarrhea, and cause neurological diseases such as meningitis and Guillain-Barré syndrome, and may also have children's multi-system inflammatory diseases similar to Kawasaki syndrome. However, most symptomatic patients present with mild to moderate respiratory diseases: such as runny nose, sore throat, cough, conjunctivitis, loss of smell and taste.

　　It is worth noting that a large proportion of COVID-19 patients have subclinical infections, and effective human-to-human transmission can be achieved in community and hospital environments. This makes symptom screening during entry ineffective, requiring extensive testing and isolation of infected persons, labor-intensive contact tracing, and social isolation or lockdown.

　　COVID-19 is believed to be spread through respiratory droplets and direct or indirect contact, but there has been no clear experimental evidence report before. Based on the evaluation of the binding affinity of common laboratory mammalian angiotensin-converting enzyme 2 (ACE2) and the receptor binding domain of the SARS-CoV-2 surface spike protein, the HKU research team recently established a golden Syrian hamster model of COVID-19 . Hamsters infected with the new coronavirus will experience shortness of breath, weight loss and acute respiratory distress syndrome (ARDS), and their tissues will also have pathological changes.

　　Using this animal model, the researchers used the hamster infected with the new coronavirus to live with uninfected hamsters, confirming that the new coronavirus can be transmitted through direct or indirect contact. However, the debate about whether there is respiratory droplets or aerosol transmission, and whether the wearing of surgical masks by the virus shedding or susceptible people can help prevent transmission has remained hot. This time, the researchers used the COVID-19 hamster model to confirm that it is possible to prevent the spread of the new coronavirus through surgical masks worn by patients or susceptible hosts.