标签： 武汉剁饼子论坛

　　According to the latest data released by Shaanxi Provincial Health and Health Commission on December 27th, from December 9th to 26th, the province reported 651 confirmed cases in COVID-19, of which 635 cases appeared in Xi ‘an. On the 25th and 26th, for two consecutive days, the number of newly confirmed cases in Xi ‘an exceeded 100 in a single day … This ancient city with a population of 10 million is being hit by the COVID-19 epidemic.

　　According to the latest news from the COVID-19 Epidemic Prevention and Control Headquarters in Xi ‘an, Xi ‘an started a new round of all-round nucleic acid screening at 12: 00 on the 27th-this is the fifth round of all-round nucleic acid testing since Xi ‘an officially announced the first round of all-round nucleic acid testing on December 19th.

　　In the past few days, Xi ‘an’s prevention and control policies have also been continuously strengthened and upgraded. On the 23rd, Xi ‘an began to implement the "Eleven Measures to Strengthen Prevention and Control", which required the city’s residential units to close their management and suspend business in non-essential places. From 0: 00 on the 27th, the city’s epidemic prevention and control measures were further strengthened.

　　Up to now, there are 1 high-risk area and 115 medium-risk areas in Xi ‘an. The battle against the epidemic continues.

　　A large number of confirmed cases were screened out by multiple rounds of total nucleic acid testing.

　　According to the news of the Office of Xi ‘an Epidemic Prevention and Control Headquarters on December 26th, Xi ‘an will usher in a new round of all-round nucleic acid testing at 12 o’clock on the 27th. The Paper (www.thepaper.cn) combed and found that this is the fifth round of total nucleic acid after the current outbreak in Xi ‘an.

　　On the afternoon of 19th, the press conference on the prevention and control of epidemic situation in COVID-19, Xi ‘an announced that all the staff in Xi ‘an had been tested for nucleic acid. Since then, on December 21st, 23rd and 25th, Xi ‘an has carried out three rounds of all-round nucleic acid testing. At present, the government has only publicly disclosed the relevant data of the second round of nucleic acid screening in Covid-19: in this round of testing, 127 cases of nucleic acid positive persons were found.

　　Several rounds of full-scale nucleic acid development have played a role in finding out the epidemic situation. The data showed that among the 155 newly confirmed cases in Xi ‘an from 0: 00 to 24: 00 on December 25th, 56 cases were found in nucleic acid screening, accounting for 36.1%. From 0: 00 to 24: 00 on 26th, among the 150 newly confirmed cases in Xi ‘an, 59 cases were found in nucleic acid screening, accounting for 39.3%.

　　Zhang Yi, director of the Institute of Infectious Disease Prevention and Control of Shaanxi Provincial Center for Disease Control and Prevention, said in an interview with Shaanxi Daily that there are two main reasons for the recent sudden increase in cases. First, the intensity of nucleic acid detection has been increased, the coverage has been increased, and the detection frequency has been increased, thus more cases have been discovered; The other is that there have been some new punctate outbreaks, such as Photoelectric Valley and JD.COM Logistics Park, and many cases have appeared in a short time. There is no need for the public to worry too much about the rapid increase of confirmed cases in the short term. At this stage, the more you find through nucleic acid testing, the better, which is also the purpose of nucleic acid testing. We have quickly taken control measures for these punctate outbreaks, and with the implementation of containment measures, the epidemic situation will tend to be flat on the whole.

　　In addition, at the epidemic conference held in Xi ‘an on 26th, the person in charge also said that through many rounds of large-scale nucleic acid screening, most hidden cases and community-infected people can be found quickly, which is beneficial to realize early detection, early isolation and early blocking, and minimize the possibility of transmission. This is the dual effect of Xi ‘an’s blockade and large-scale screening. There may be more reported cases in the next few days of nucleic acid screening, reminding citizens and friends not to panic.

　　Strengthen and upgrade prevention and control measures.

　　With the increasing epidemic situation in Xi ‘an, the prevention and control measures have been strengthened and upgraded many times.

　　On December 15th, a press conference was held in Xi ‘an, and relevant departments advised citizens not to leave the city unless necessary. It is proposed that people in medium and high-risk areas and their districts and counties should strictly restrict travel; Personnel from other districts and counties in the city where the medium and high-risk areas are located do not have to travel unless necessary. If they really need to travel, they must hold a negative nucleic acid test certificate within 48 hours. All people from other provinces who return to Xi ‘an need to provide negative proof of nucleic acid test within 48 hours.

　　On December 18th, the control was upgraded. It is clear that all personnel in this city who do not really need to leave the city must hold a negative nucleic acid test certificate within 48 hours. Bar dance halls, sports and fitness, theaters, mahjong halls, script killing, bathing and other indoor entertainment venues are closed. Retail pharmacies suspend the sale (including online sales) of antipyretic, antitussive, antiviral and antibacterial drugs to the public.

　　On the 20th, primary and secondary schools and kindergartens in the city were closed. Citizens need to hold a negative report of nucleic acid test within 48 hours when they go to work.

　　Starting from the 22nd, people who leave Xi ‘an by bus from Xi ‘an Railway Station and Xi ‘an North Railway Station must not only hold the negative certificate of 48-hour nucleic acid test and the green code of one code, government code and itinerary code, but also the personnel of party and government organs and state-owned enterprises and institutions need to leave Xi ‘an with the necessary official letter issued by the unit and the examination and approval procedures of the main person in charge; Other personnel also need to hold an official letter issued by the street office, township and the main person in charge of examination and approval procedures. In addition, the city’s long-distance passenger lines were suspended.

　　From 0: 00 on the 23rd, Xi ‘an officially implemented eleven measures to strengthen prevention and control. In particular, it is mentioned that all communities (villages) and units in the city are required to implement closed management, and the citizens generally live at home. Every family can assign one family member to go out to purchase daily necessities every two days, and other family members generally do not go out except to participate in epidemic prevention and control, get sick and seek medical treatment, and are in urgent need of work.

　　From 0: 00 on the 27th, Xi ‘an further strengthened the city’s epidemic prevention and control measures. Suspended the previous "two-day-one-out" purchase policy. It is required that all residents do not leave home or gather except for participating in nucleic acid sampling as required. Residents in the prevention area can only implement the original purchase regulations after completing a new round of nucleic acid sampling and showing negative results.

　　The epidemic prevention and control headquarters of COVID-19 in Xi ‘an said that after the completion of this round of nucleic acid screening on 27th, the control measures will be adjusted according to the test results.

　　Fully protect the lives of citizens.

　　Since the implementation of the closed management of residential quarters on the 23rd, some citizens in Xi ‘an have been worried about their daily life: Will the price of living materials increase? How to ensure the treatment of daily diseases?

　　Zhang Fenghu, deputy director of the Office of Xi ‘an Epidemic Prevention and Control Headquarters and deputy secretary-general of the municipal government, previously publicly stated, "We will further improve the monitoring, analysis and early warning mechanism of the’ vegetable basket’ market and price, and closely track and analyze market supply and demand and price changes. Severely crack down on illegal activities such as driving up prices, hoarding, making and selling fake goods in key medical prevention and control materials and daily necessities. Strengthen the visits of people with difficulties in life, and timely include eligible objects in the scope of assistance to ensure basic living. Street communities and units should grasp the medical needs of special people in a timely manner, provide basic health services first, and help those who really need to go out for medical treatment with personal protection. "

　　The Paper noted that in terms of price protection, the Xi ‘an Municipal Market Supervision Administration has investigated and dealt with more than ten illegal incidents, which involved price gouging or unclear pricing. In a supermarket, the price of cabbage increased by 2 yuan per catty within two days, and it was fined 50,000 yuan.

　　For some patients with special diseases, Xi ‘an has also taken corresponding safeguard measures. For example, among the management personnel, patients with chronic renal insufficiency (uremia) need hemodialysis (hemofiltration) urgently. At present, Xi ‘an High-tech Hospital has been designated as the designated hospital for hemodialysis (hemofiltration) of isolated control personnel in the near future.

　　Yang Baoli, the second-level inspector of Shaanxi Provincial Health and Health Commission, said that he would spare no effort to ensure the urgent need for dialysis for patients with chronic renal insufficiency (uremia) in isolation and control areas during the epidemic prevention and control period, so that patients with isolation and control can be treated in time.

　　According to Xi ‘an Daily, Xi ‘an has arranged a number of hospitals, such as the First Affiliated Hospital of Xi ‘an Jiaotong University and the First Hospital of Xi ‘an, to provide online consultation services for citizens to meet their medical needs.

　　In addition, in order to protect the public’s health and life safety, the Xi ‘an Epidemic Prevention and Control Headquarters decided to carry out a comprehensive disinfection in Xi ‘an from 18: 00 on the 26th.

It seems that the dual-clutch gearbox has always had a bad reputation in the market, saying that it is all kinds of setbacks, and then the low-speed shift is irregular, and there are some design defects and some ghosts. Actually, I agree with you.

Although the dual clutch does bring some uncomfortable experiences at low speed, it also has its own outstanding advantages, such as high shift efficiency and fast shift speed, and makes the power almost seamlessly connected. However, there are also wet and dry types in powershift. Generally speaking, the wet type will be better, because the heat dissipation will be better, and it will not prompt the gearbox to overheat and then start the overheating protection because of a little intense driving …

Because of the special structure system and logical thinking of the dual clutch, it still needs some skills to be "comfortable" when driving a dual clutch vehicle. Let me give the dual clutch a wave of "rehabilitation".

Don’t let the clutch whine

Many owners of dual clutch gearboxes complain that their dual clutches are easily broken, but most of them are caused by improper use. For example, when stopping at a red light, many car owners like to step on the brakes, and then the car stops, just fine. The brakes are not stepped to the end. In fact, this is very burning the clutch plate, which is equivalent to the manual car stepping on the brakes without stepping on the clutch. Originally, the clutch plate was replaced about 80 thousand kilometers, and then the clutch plate of 50 thousand kilometers was GG.

Make more use of neutral position

Many old drivers like to stop and step on the foot brake, which is very irrational and even stupid. N-block is for you to stop for a short time. Others are good to say. If the vehicles in powershift keep stepping on the brakes when parking, the loss of your vehicles will be much greater than others. So it’s always right to park in N gear and be diligent.

Remember to step on the brake to the end.

If you change gears frequently in traffic jam, it will be troublesome, so I will teach you a method, that is, brake to the end, so that the clutch plate will loosen, because the computer has detected that you have to park.

Don’t worry about starting.

Many car owners who drive dual clutch vehicles often report that when they start in D gear, they don’t understand when they step on the accelerator. This is because the clutch plate will have 0.7 seconds to engage in the semi-clutch state after you put it in gear, so the engine will idle before stepping on the accelerator, and the best way is to wait for the idle speed to bring the car up before stepping on the accelerator.

Try to avoid low-speed peristalsis

Many times, when a female driver with dual clutch stops in the basement, the temperature of the gearbox is too high and she needs to stop to dissipate heat because of moving the car for a long time. That’s because the clutch plates are always in a state of semi-linkage. If the friction time is too long, the protection mechanism will be activated. Therefore, when driving a dual-clutch car at a low speed, it must be wretched and don’t wave.

　　Covid-19 is thought to originate from bats, and it is 96.2% similar to RaTG13 (collected by Shi Zhengli, Wuhan Institute of Virology, Chinese Academy of Sciences, in Yunnan, China in 2013) in nucleotide sequence level. However, it is a kind of novel coronavirus that has not been detected in humans and other animals before, and its appearance has brought many new problems to be solved urgently, including whether other pets, livestock and poultry may be infected by Covid-19 besides humans?

　　On April 8th, local time, the top academic journal Science published the paper "Susceptibility of Ferrets, Cats, Dogs, and Different Domestic Animals to SARS-coronavirus-2" online. The purpose of this study is to find out some questions: Will Covid-19 be transmitted to other animal species, thus becoming a "reservoir" of infection? Covid-19 infection has many clinical manifestations in humans, ranging from mild infection to death, so how is it manifested in other animals? With the development of vaccines and antiviral drugs, which animals can be used to simulate the effects of these drugs or vaccines on humans most accurately?

　　In order to solve these problems, research teams from the State Key Laboratory of Veterinary Biotechnology of Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences and the National High-level Biosafety Laboratory of Animal Disease Prevention and Control evaluated the susceptibility of different model experimental animals, pets and livestock to Covid-19, infected Covid-19 through experiments, observed the clinical manifestations and pathological changes of vaccinated animals and cohabiting animals, and detected the viral load of organs and tissues, the emission of respiratory and intestinal viruses, and the seroconversion of antibodies against Covid-19 in animals.

　　Their research shows that Covid-19 has weak replication ability in dogs, pigs, chickens and ducks, but it can replicate efficiently in ferrets’ upper respiratory tract and cats’ respiratory system and digestive system. Experimental infected cats can spread Covid-19 through the air; Some cats can cause serious illness or even death after infection, and the illness of young cats is obviously more serious than that of older cats.

　　Histopathological observation confirmed that virus infection in cats can cause lung inflammation and intestinal mucosal damage to varying degrees. Immunohistochemical study showed that there were a large number of virus infections in mucosal epithelium and olfactory bulb cells of upper respiratory tract (nasal cavity, maxilla, tonsil), mucous gland epithelial cells of trachea and bronchial mucosa, and intestinal mucosal epithelium.

　　The correspondent of this paper is Chen Hualan, academician of China Academy of Sciences, chief scientist of the innovation team of animal influenza basic and prevention research in Harbin Veterinary Research Institute of China Academy of Agricultural Sciences, Bu Zhigao, director of Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences and director of the national high-level biosafety laboratory for animal disease prevention and control, and Wu Guizhen, secretary of the Party Committee of Institute of Viral Disease Prevention and Control of China CDC and director of BSL-3 laboratory. Previously, on March 31st, local time, the research team had taken the lead in publishing the research on the preprint platform bioRxiv.

　　It is worth mentioning that the National High-level Biosafety Laboratory for Animal Disease Prevention and Control is one of the existing two P4 laboratories in China, and the other is in Wuhan National Biosafety Laboratory of Chinese Academy of Sciences. All the experiments of Covid-19 infection in this study were carried out in P4 laboratory, which was approved by the Ministry of Agriculture and Rural Affairs of China. Animal research and animal welfare programs were approved by the Animal Experimental Ethics Committee of China Academy of Agricultural Sciences.

　　According to the press release issued by official website, Harbin Veterinary Research Institute of Chinese Academy of Agricultural Sciences, different coronaviruses have been prevalent in mammals and poultry, but most of these coronaviruses are limited to specific species of animals and generally cannot infect humans. Similarly, several common coronaviruses in humans do not infect other animals. However, some coronaviruses from bats, such as SARS and MERS virus, can often infect many animals and humans.

　　At present, Covid-19 is popular among a wide range of people in the world, and the risk of introducing animals in close contact with human beings is increasing. Therefore, it is urgent to study the susceptibility of domestic animals in close contact with human beings to Covid-19, evaluate whether domestic animals are exposed to Covid-19 hazards and become potential intermediate hosts, and provide scientific basis for prevention and control of Covid-19.

　　In addition, in view of the current global epidemic situation of COVID-19, it is very likely that it will evolve into a common infectious disease, and it is urgent to establish a stable and reliable animal infection model to meet the needs of vaccine and drug research and development evaluation.

　　The research team stressed that the monitoring of cat COVID-19 should be regarded as an auxiliary means to eliminate the current Covid-19 epidemic. They called for close monitoring and protection of cats in epidemic areas, avoiding their contact with infectious sources and preventing them from becoming possible transmission hosts or storage hosts.

　　In addition, it was previously questioned that cats infected with COVID-19 were caused by large doses under laboratory conditions. However, in addition to this research, on April 3rd, Academician Jin Meilin, professor of the State Key Laboratory of Agricultural Microbiology of Huazhong Agricultural University, director of the Key Laboratory of Veterinary Diagnostic Preparations of the Ministry of Agriculture, director of the Research Center for Emerging Infectious Diseases of Wuhan Institute of Virology, Chinese Academy of Sciences, and researcher Shi Zhengli, director of the Key Laboratory of Highly Pathogenic Biology and Biosafety of Chinese Academy of Sciences, also published a study on the preprint platform bioRxiv. Through the investigation of cat serum, they found that the serum ELISA test of 102 cats collected after the outbreak of COVID-19 in Wuhan showed that the serum from 15 cats (14.7%) was positive for Covid-19 receptor binding domain (RBD).

　　Nadia, a 4-year-old tiger from Bronx Zoo in new york, USA, was recently diagnosed with Covid-19. On April 5, local time, the US Department of Agriculture issued a statement confirming that a tiger in a zoo in new york was diagnosed with Covid-19, and several other lions and tigers also showed symptoms of respiratory diseases. Officials at the Bronx Zoo in new york said that nadia, three other tigers and three African lions had symptoms of dry cough and loss of appetite, but they are expected to recover. Public health officials believe that these animals were infected by an asymptomatic employee.

　　Covid-19 can be replicated in the upper respiratory tract of ferrets for up to 8 days, but it will not cause serious illness or death.

　　Ferrets are often used as animal models of human respiratory viruses. Therefore, the research team first tested ferrets’ sensitivity to Covid-19.

　　Two Covid-19 strains were used in this study: F13-E from Wuhan South China Seafood Market and CTan-H from a patient infected with Covid-19.

　　The research team inoculated 10 5 PFU (Plaque Forming Unit) F13-E or CTan-H into ferrets through nose respectively, and euthanized them on the 4th day after inoculation (P.I.). The turbinate, soft palate, tonsil, trachea, lung, heart, spleen, kidney, pancreas, small intestine, brain and liver of each ferret were collected, and the viral RNA was determined by qPCR and virus titration.

　　Viral RNA：A in ferrets’ organs or tissues: A, F13-E, B, CTAN-H..

　　The results showed that viral RNA and infectious virus were detected in the turbinate, soft palate and tonsil of all four ferrets, but not in other tissues.

　　C, virus titer in organs or tissues of ferrets inoculated with F13-E, D and CTAN-H.

　　The research team believes that these results show that Covid-19 can replicate in the upper respiratory tract of ferrets, but it has not been detected in other tissues.

　　In order to study the replication dynamics of virus in ferrets, the research team intranasally inoculated 6 ferrets with 10^5pfu of F13-E(3) or CTan-H(3), and then placed them in three isolated cages. On the 2nd, 4th, 6th, 8th and 10th day, ferret nasal wash and rectal swab were collected for virus RNA detection and virus titration. At the same time, their body temperature and COVID-19 signs were monitored for two weeks.

　　Viral RNA in the nasal wash of ferrets inoculated with F13-E(E) and CTan-H(F). Viral titers in the nasal wash of ferrets inoculated with F13-E(G) and CTan-H(H).

　　The results showed that viral RNA was found in the nasal wash of all six ferrets on the 2nd, 4th, 6th and 8th day. Viral RNA was also found in some rectal swabs, but the copy number was significantly lower than that of nasal wash. Infectious virus was detected in nasal wash of all ferrets, but none of them was found in rectal swab.

　　One ferret in each group developed fever and loss of appetite on the 10th and 12th days respectively. In order to investigate whether these symptoms are caused by virus replication in the lower respiratory tract, the research team euthanized the two ferrets on the 13th day and collected their organs for virus RNA detection.

　　However, except for the ferret turbinate inoculated with CTan-H, the low copy number was detected, and no viral RNA was detected in any other tissues or organs.

　　Pathological studies showed that two ferrets euthanized on the 13th day had severe lymphoplasmacytic vasculitis and vasculitis, the number of type II alveolar cells, macrophages and neutrophils in alveolar septa and alveolar cavities increased, and the lungs had mild bronchiolitis.

　　The asterisk indicates that the animals were euthanized on the 13th day after inoculation, and the other four animals were euthanized on the 20th day.

　　Covid-19 antibody was detected in all ferrets by ELISA and neutralization test, and the antibody titers of two ferrets euthanized on the 13th day were significantly lower than those euthanized on the 20th day.

　　In order to further study whether Covid-19 was replicated in ferrets’ lungs, the research team inoculated 8 ferrets with 10^5 pfu of CTan-H through trachea, and euthanized 2 animals on the 2nd, 4th, 8th and 14th days, respectively, and detected virus RNA in tissues and organs.

　　Among the two ferrets euthanized on the second day and the two ferrets euthanized on the fourth day, the researchers only detected viral RNA； in the turbinate and soft palate of one of them. Among the two ferrets euthanized on the eighth day, viral RNA； was detected in the soft palate of one ferret and in the turbinate, soft palate, tonsil and trachea of the other ferret. No viral RNA was detected in the two ferrets euthanized on the 14th day.

　　These results indicate that Covid-19 can replicate in the upper respiratory tract of ferrets for up to 8 days without causing serious illness or death.

　　At the end of the paper, the research team also mentioned that, comparatively speaking, Covid-19 is different from other influenza viruses that can replicate in the upper respiratory tract and lower respiratory tract of ferrets, and even human SARS-CoV. Covid-19 is only replicated in ferrets’ nasal bones, soft palate and tonsils. It can also replicate in the digestive tract, but even if the virus is inoculated in the trachea, the virus is still not detected in the lungs of ferrets.

　　Cats are highly susceptible to "cat-to-cat transmission": the monitoring of cat Covid-19 should be regarded as an auxiliary means of epidemic prevention and control.

　　It is worth noting that cats and dogs are in close contact with humans, so the research team thinks that besides laboratory animals like ferrets, it is very important to know the susceptibility of domestic animals that often live with humans to COVID-19 for the control of Covid-19.

　　The research team first studied the replication of Covid-19 in cats. Five 8-month-old subadult domestic cats (inbred lines) were intranasally inoculated with 10^5pfu of CTan-H, and two of them were scheduled to be euthanized on the sixth day to evaluate the virus replication in their organs. Three cats were put in separate cages in the isolator. In order to monitor the spread of respiratory droplets, an uninfected cat was placed in a cage adjacent to each cat vaccinated with the virus.

　　Because 8-month-old cats are aggressive, it is difficult to carry out routine nasal cleaning on them. In order to avoid possible harm, the research team collected the feces of these cats and checked the viral RNA in their organs after euthanasia.

　　Virus RNA was detected in the nasal bone, soft palate and tonsils of two sub-adult domestic cats euthanized on the 6th day, and virus RNA was also detected in the trachea of one cat and the small intestine of the other cat. However, no viral RNA was detected in any lung samples of these two cats.

　　Infectious viruses were detected in the nasal bones, soft palate, tonsils and trachea of these cats, but no infectious viruses were found in the small intestine with positive viral RNA.

　　The spread of Covid-19 among cats.

　　In the study of virus transmission, RNA virus was detected in the feces of two vaccinated cats on the third day, and RNA virus was detected in the feces of all three vaccinated cats on the fifth day. Among the three cats at risk of virus exposure, viral RNA was detected in the feces of one cat on the third day.

　　Virus-infected cats with positive feces were euthanized on the 11th day. Virus RNA was detected in the soft palate and tonsils of the infected cats and in the nasal bones, soft palate, tonsils and trachea of the exposed cats, indicating that respiratory droplets spread between cats.

　　On the 12th day, the research team euthanized the remaining cats. Viral RNA was detected in the tonsils of one virus-infected cat and the nasal bone, soft palate, tonsils and trachea of another virus-infected cat, but it was not detected in any organ or tissue of the two virus-exposed cats.

　　Through ELISA and neutralization test, Covid-19 antibody was detected in all three cats inoculated with virus and one cat exposed to virus.

　　Covid-19 replicates efficiently in respiratory system and digestive system of infected cats, causing pathological damage and inflammatory reaction. Histopathological and immunohistochemical study on cats that died or were euthanized three days after virus infection. (a) The arrangement of nasal mucosa epithelium is disordered, cilia fall off (arrow), and lymphocytes in lamina propria infiltrate (arrow). (b) The tonsil epithelial cells are degenerated and necrotic, and the surface of mucosal epithelium (asterisk) is covered with cell fragments and neutrophils (arrow). (c) Epithelial degeneration and necrosis of tracheal mucosa (arrow), with mucus (asterisk) mixed with a large number of cell fragments on the surface. (d) Epithelial necrosis of tracheal mucous glands and infiltration of lymphocytes (arrow). (e) Normal lung tissue structure of uninfected cats. (f) Aggregation of inflammatory cells in pulmonary blood vessels and coagulation of fibrin (arrow). (g) A large number of macrophages and lymphocytes infiltrated in alveoli, that is, alveolar septa. (h) Infiltration and proliferation of alveoli and alveolar septitis. (i) Some cells in the epithelium of small intestine are degenerated and necrotic, and lymphocytes in the lamina propria are moderately infiltrated (arrow). (j) A large number of epithelial cells of turbinate mucosa were positive for virus antigen (brown). (k) A large number of exfoliated cells in tonsil mucosa epithelium and mucosa surface were positive for virus antigen (brown). (l) A large number of virus antigens were positive (brown) in serous cells of tracheal mucous glands. (m) A large number of small intestinal mucosal epithelial cells were positive for virus antigen (brown). Ruler line A, I = 100 μ m, B-H, J-L = 200 μ m, M = 500 μ m

　　The research team also repeated the above-mentioned replication and transmission research in sub-adult cats in young cats (70-100 days). Histopathological studies on the samples of young cats who died or were euthanized on the third day after being inoculated with the virus showed that the nasal cavity and tracheal mucosa epithelium and lungs of the two cats had a lot of damage.

　　These results indicate that Covid-19 can be effectively replicated in cats, and young cats are more susceptible to infection. More importantly, the virus can spread from cat to cat through respiratory droplets.

　　Next, the research team also studied the replication and spread of Covid-19 in dogs, and the results showed that dogs were less sensitive to Covid-19. Similar studies also show that pigs, chickens and ducks are not sensitive to Covid-19.

　　Overall, the research team found that ferrets and cats are highly sensitive to Covid-19, dogs are less sensitive, and domestic animals including pigs, chickens and ducks are not sensitive to the virus.

　　In addition, it is reported that Covid-19 uses angiotensin-converting enzyme 2 (ACE2) as its receptor to enter cells, and ACE2 is mainly expressed in type II lung cells and serous epithelial cells of ferrets’ tracheal-bronchial submucosal glands. Therefore, the research team believes that the potential mechanism to prevent Covid-19 from replicating in ferrets’ lower respiratory tract remains to be studied.

　　The results of this study show that ferrets can be used as animal models for vaccine and drug evaluation in Covid-19. Dogs, pigs, chickens and ducks are not susceptible to Covid-19, which has important guiding significance for the traceability of virus hosts; More importantly, cats are highly susceptible to Covid-19.

　　The research team called for close monitoring and protection of cats in epidemic areas to avoid contact with infectious sources and prevent them from becoming possible transmission hosts or storage hosts. The monitoring of cat COVID-19 should be regarded as an auxiliary means to eliminate the current Covid-19 epidemic.

　　Paper link: https://science.sciencemag.org/content/sci/early/2020/04/07/science.abb7015.full.pdf.