埃博拉病毒病 z-bo 2020-12-17 324

　　Ebola virus disease (EVD) is an acute infectious disease caused by Ebolavirus (EBOV) infection, with a fatality rate of 90%. The highly contagious, highly pathogenic, and high fatality EVD epidemic that broke out in Guinea in December 2013 was the largest in 38 years since the disease was discovered, with the largest number of infections and deaths.

　　On August 8, 2014, the WHO declared the EVD epidemic as a “public health emergency of international concern”. According to the latest data released by the WHO, there have been more than 1,840 deaths due to EVD globally, and more than 3685 confirmed, suspected and possibly infected cases have been accumulated. Among them, Guinea, Liberia and Sierra Leone in West Africa are the most affected. What is even more frightening is that EVD has It spread from Africa to Europe (Spain) and America (USA). WHO predicts that if the epidemic cannot be effectively controlled, the number of EVD cases and deaths will increase from a few hundred cases per week to several thousand cases per week within a few months. By early November 2014, the number of EVD patients in West Africa will exceed 20,000. .

　　As there are no effective antiviral drugs and vaccines, the WHO has listed EBOV as a biosafety level 4 virus. my country and West African countries have close personnel exchanges in labor, business, study abroad and education. Although there is no EVD epidemic in China, there is a risk of losing people at any time. Therefore, it is necessary to deepen scientific understanding of the disease and prepare for response.

　　One, etiology

　　EBOV is the pathogen of EVD. It was discovered in 1976. The first outbreak occurred in a village near the Ebola River in Zaire, where "Ebola" got its name. EBOV belongs to the family of filoviruses. It is a single-stranded negative-stranded RNA virus consisting of about 19X103 bases. The virus with an average length of 1000nm (665nm~805nm) has a strong ability to infect viruses. EBOV has diverse morphologies, branched and U Shaped, rod-shaped, filamentous or circular, etc.; there is a spiral nucleocapsid with a glycoprotein envelope. EBOV can be divided into five subtypes: Zaire type, Sudan type, Bundibujo type, Tay forest type and Reston type. Except Reston type is not pathogenic to humans, the other four subtypes are infected Later, it can cause human disease, and the pathogenicity is Zaire, Sudan, Bundibujo, and Tay Forest in order from strong to weak. The first three subtypes have caused human EVD epidemics, and the fatality rate is 50% to 90%, of which the Zaire type accounted for 15 of the 25 global outbreaks.

　　Whole-gene sequencing analysis showed that the EBOV that originally occurred in Guinea has 97% homology with the known Zairian EBOV originating from the Congo and Gabon Republic, and belongs to the Zairian type. The current mainstream view is that although the EBOV of Guinea and the EBOV of the Republic of Congo and Gabon belong to the same parallel evolutionary tree, they have formed independent clades and are not inherited from the Republic of Congo and Gabon. However, some German scientists still believe that the EBOV may be caused by Descendants from Central African countries. The phylogenetic analysis of the full-length sequence shows that the Guinea EBOV strain is a new type of Zairian variant, which may make EBOV more easily infected. EBOV is relatively stable at room temperature. There is no significant change in virus infectivity after 1 month storage at room temperature and 4°C; moderate high temperature resistance, but it can be inactivated at 60^1h, while it can be inactivated at 100°C for 5min; UV rays It can be inactivated by irradiation for 2 minutes; it is sensitive to disinfectants such as formaldehyde, hypochlorous acid and helix, but the virus cannot be inactivated by freezing or refrigeration.

　　2. Pathogenic mechanism "In situ hybridization and electron microscopy showed that EBOV can invade monocytes, macrophages, DC, fibroblasts, hepatocytes, adrenal cells, and a variety of endothelial and epithelial cells. After EBOV infects the body, it binds to human cells through the spike glycoprotein and receptors on the surface of the host cell membrane. The infected monocytes and macrophages express a variety of cytokines closely related to abnormal blood coagulation, and promote blood coagulation mechanisms. Lead to coagulation factor imbalance and subsequent coagulation dysfunction, causing coagulation in tiny blood vessels, causing ischemic necrosis of organs such as liver, spleen, kidney and adrenal glands, and ultimately causing diffuse intravascular coagulation (DIC) or multiple organ failure (MODS) . Theoretically, patients with viral infections are eventually cured by inducing the body's immune response to produce protective antibodies to clear the virus. EBOV targets human monocytes, macrophages and DCs and other mononuclear phagocyte systems under the mediation of viral envelope glycoproteins. The mononuclear phagocyte system as the host of EBOV not only cannot eliminate EBOV, but also promotes the proliferation of the virus. Transport and diffusion, thereby preventing the production of interferon with antiviral effect, reducing the activity of interferon produced, promoting the apoptosis of NK cells and lymphocytes in the body, and finally inhibiting the host's acquired and natural immune response, resulting in many patients Death before the emergence of an effective antiviral immune response is one of the reasons for the high fatality rate of EVD.

　　Current research shows that the pathogenesis of EBOV may be related to the viral proteins GP, VP35, VP40, VP30 and VP24. GP can mediate EBOV into human host cells by binding to the receptor; destroying the integrity of capillaries by binding to vascular endothelial cells, causing blood leakage; and may also interfere with the killing effect of immune cells on EBOV. VP35 can hinder the formation of dsRNA and type I interferon promoter during EBOV replication, and has anti-interferon effect; VP40 may participate in the budding process of EBOV; VP30 can bind to the DNA double helix structure to activate the transcription of EBOV; VP24 can interact with Co-expression of GP produces infective EBOV particles, which participate in virus assembly and budding release.

　　3. Epidemiological characteristics

　　EVD first appeared in two simultaneous outbreaks in 1976, one in Nzala in southern Sudan and the other in Yanbuku (Old Zaire), Democratic Republic of Congo. Since then, local epidemics have formed in some countries in central and western Africa. A total of 24 epidemics were reported from 1976 to 2012, with a cumulative number of more than 2,300 cases, with a fatality rate of 40% to 90% and an average fatality rate of 67%.

　　Zaire type caused the most outbreaks (5 times), with a case fatality rate of 44% to 90%; Sudan type caused the second largest number of epidemics (7 times), with a case fatality rate of 41% to 71%. The current Ebola epidemic in West Africa first broke out in the forest areas of southeastern Guinea (Gai Kizhuang, Masanda, and Gisidugu). The source of the outbreak may be a two-year-old boy from Guinea who died 4 days after the onset of illness. Later, his mother, sister, grandmother, and people attending the funeral died of illness, but it is still unclear how the boy was infected with EBOV.

　　Since then, the Guinea epidemic has spread to Sierra Leone, Liberia, Nigeria, Senegal, the Democratic Republic of the Congo, Spain and the United States. The EBOV virus sequence was found in fruit bats near the human EVD epidemic site, suggesting that the big bat family fruit bats may be the natural host of EBOV; humans and non-human primates infected with EBOV can be the source of infection, but EBOV in nature The circulation method is unclear. WHO conducted a detailed analysis of 3343 confirmed cases and 667 suspected cases that occurred in Guinea, Liberia, Nigeria and Sierra Leone before September 14, 2014. The results showed that most EVD patients were 15 to 44 years old, and 49.9% of the patients Male; the case fatality rate of confirmed EVD patients is 70.8%, of which the case fatality rate of hospitalized patients is 64%; the series interval (that is, the time from infection to transmission of the virus) averages 15.3 days. The study showed that people are generally susceptible to EBOV, and there is no age and gender difference. The infected population is mainly adults, which may be related to exposure or exposure.

　　4. Clinical manifestations and routine laboratory examinations

　　The incubation period of EVD can last for 2 to 21 days, generally 5 to 12 days. Current data show that EVD is not infectious during the incubation period. EVD has an acute onset, with early symptoms such as high fever, chills, extreme fatigue, headache, myalgia, sore throat, etc. Some infected people will have symptoms such as conjunctival hyperemia and dyspnea; vomiting, abdominal pain, etc. may occur after 3 days. Diarrhea, mucus or blood in the stool, etc., enter the extreme stage after 4 to 5 days, the patient develops persistent high fever, symptoms of infection and poisoning and aggravation of gastrointestinal symptoms, accompanied by different degrees of bleeding, including skin and mucosal bleeding, hematemesis, hematemesis, hemoptysis and hematuria, etc. , At the same time, there may be mental changes, such as delusion, lethargy, etc.

　　50% to 90% of patients died within 2 weeks of onset, the main cause of death was hypovolemic shock, DIC or MODS. Severe bleeding tendency, anuria, hiccups, and shortness of breath during the course of the disease indicate a poor prognosis.

　　The long-term survival rate of patients who are still alive within 2 weeks of onset can reach 70%. EVD patients may develop a measles-like rash during the course of 5 to 7 days, that is, local skin with red macules, which can subside and desquamation within a few days to 2 weeks, and some patients may have skin changes for a long time. The above-mentioned clinical manifestations are not typical and are easily confused with malaria, typhoid fever, and dengue fever. The results of routine laboratory examination showed that the counts of white blood cells and platelets were decreased and heterogeneous lymphocytes appeared; prothrombin time was prolonged, and fibrin degradation products increased; liver function showed that ALT and AST were both increased; as kidney injury worsened, blood Urea nitrogen and creatinine increased progressively.

　　Five, diagnosis

　　According to epidemiological data, clinical manifestations and routine laboratory examination results, the diagnosis of clinical suspected cases can be made, and the diagnosis mainly depends on pathogenic examination.

　　1. Detection of nucleic acid and virus antigen: The current diagnosis of EBOV infection mainly relies on fluorescent PCR to detect viral nucleic acid and enzyme-linked immunoassay to detect EBOV nucleoprotein antigen. Within 3 days after the onset, the detection rate of EBOV nucleic acid and nucleoprotein antigen in blood samples was low, and the detection rate was high 3-10 days after the onset. The latest literature reports that the real-time fluorescent reverse transcription (RT)-PCR detection method can specifically detect 10 copies/uL of EBOVRNA, and the correlation coefficient of the standard curve is >99%; for the EBOV nuclear protein gene (ZEBOV-NP) and Glycoprotein gene (ZEBOV-GP) designed specific primers and probes, and established a dual real-time fluorescent RT-PCR detection method, which can detect 100pfu/mL EBOV, with sensitivity and specificity >95%.

　　2. Antibody test: detect the specific EBOVIgM antibody and IgG antibody in the serum. IgM antibody positive can be diagnosed. A single serum IgG antibody positive indicates that you have been infected with EBOV. The IgG antibody titer is more than 4 times higher than the acute phase to confirm EVD. Specific IgM antibodies can be detected in the serum of patients 2 days after the onset of the disease at the earliest. IgM antibodies can be maintained for several months, and IgG antibodies can be detected 7-10 days after the onset, and IgG antibodies can be maintained for several years. 3. Virus isolation: collect blood samples from patients with acute fever, and use Vera and Hela cells for virus isolation and culture. Generally, the virus isolation rate in blood samples is high within 1 week of onset; however, it must be performed in a biosafety level 4 laboratory. This project cannot be carried out yet.

　　In addition, it has also been reported that EBOV particles can be found in the serum of EVD patients using electron microscope observation; EBOV can also be identified and typed by sequencing the L gene or the entire gene of EBOV.

　　Six, treatment progress At present, the treatment of EVD patients mainly adopts symptomatic and supportive treatment, focusing on the treatment of bleeding, secondary infection, electrolyte imbalance, hypovolemia/septic shock, DIC, acute renal failure (ARF) and even MODS; for EVD So far, there is no proven effective antiviral drug. Among the anti-EBOV drugs in the research and development stage, the monoclonal antibody combination ZMapp, RNA interference drug TKM-Ebola, and small molecule antiviral drug T-705 have received special attention and attention, and they are preparing to enter into phase I clinical trials for approval. There is hope here Played a role in the global epidemic.

　　① On August 21, 2014, British Reuters reported that two American medical staff who were infected with EBOV in Africa showed improvement after using the experimental drug ZMapp, which has attracted widespread international attention. ZMapp is an optimized combination of neutralizing antibodies MB-2003 and ZMAb. It can not only neutralize EBOV, but also stimulate non-specific immune responses in the body. It is currently the most promising anti-EBOV drug, but ZMapp is currently still in the pre-clinical trial stage. It is used in patients based on the US FDA's "sympathetic medication" regulations. ②TKM-Ebola is a gene therapy drug, a small interfering RNA (siRNA), specifically targeting EBOV-related genes VP24, VP35 and RNA polymerase dependent on RN, through RNA interference to silence the related protein RN, to achieve The purpose of preventing the proliferation of viruses. However, in the Phase I clinical trial, 14 safe subjects experienced drug reactions such as nausea, chills, hypotension, and shortness of breath. FD Eight announced the suspension of the clinical trial of TKM-Ebola on July 21, 2014, August 8, 2014 On August 8th, FD announced that, considering that the Ebola epidemic in West Africa is still spreading, it has decided to allow the continuation of the phase I clinical trial of TKM-Ebola again. ③T-705 (favipiravir, favipiravir) is a kind of RNA polymerase inhibitor, which can selectively inhibit the activity of RN eight polymerase in cells, cause disorder of RNA virus replication process, thereby hinder virus proliferation, and has broad-spectrum anti-virus active. Two pre-clinical studies have shown that TT-705 has a good inhibitory effect on Zairian EBOV in cell culture and animal experiments, and the survival rate of animal models reaches 100%. In addition, the molecular chaperone heat shock protein 5 of the endoplasmic reticulum is a host protein related to EBOV, which is essential for virus replication and can be used as a therapeutic target; small molecule probes targeting the ppxy-Nedd4 interface between the virus and the host have a wide range of The anti-RN eight virus effect may also bring dawn to the treatment of EVD in the future. Which drug will become the first "antidote" for anti-EBOV still needs to be verified by clinical trial results.

　　Seven, EVD vaccine development progress

　　The nucleotide composition of the genomes of different EBOV subtypes is quite different, but the virus genomes of the same subtype are relatively stable, which makes it possible for scientists to develop vaccines. From September 29 to 30, 2014, the WHO held an Ebola vaccine consultation meeting and reached a consensus: a vaccine product that has been fully tested and licensed should be proposed so that it can be expanded for mass vaccination campaigns.

　　However, there is currently no licensed vaccine, but there are three promising vaccines in phase I clinical trials. ①cAd3-ZEBOV is an adenovirus vector vaccine jointly developed by GlaxoSmithKline and the National Institute of Allergy and Infectious Diseases. The vaccine uses an adenovirus vector derived from chimpanzees, in which the EBOV gene is embedded.

　　②rVSV-ZEBOV is a recombinant vesicular stomatitis virus vector vaccine developed by the Public Health Agency of Canada. The vaccine uses an attenuated or weakened vesicular stomatitis virus (a pathogen found in livestock) and replaces a gene in the virus with the EBOV gene.

　　③On December 5, 2014, the "2014 Gene Mutation Recombinant Ebola Vaccine" independently developed by the Chen Wei team of the Chinese Academy of Military Medical Sciences was approved to enter the Phase I clinical trial. This is the third Ebola vaccine in the world to enter Phase I clinical trials after cAd3-ZEBOV in the United States and rVSV-ZEBOV in Canada. Compared with the previous two 1976 genotype liquid vaccines, the 2014 gene mutant recombinant EBV vaccine Bora vaccine is more targeted for the prevention and control of the epidemic, and it is the first freeze-dried powder formulation, which can be stored stably for more than 2 weeks at 37°C, breaking through the limitation of 1976 genotype liquid vaccine requiring storage and transportation at 80°C. It is more suitable for widespread use in tropical regions of West Africa where vaccine cold chain conditions are difficult to guarantee.

　　8. Preventive measures

　　The general principle of infectious disease prevention is to control the source of infection, cut off the route of transmission, and protect susceptible people. Since the population is generally susceptible to EBOV and there is no effective vaccine approved, the focus of prevention is on the first two measures. Once a suspected EVD patient is found, strict isolation measures should be taken and admitted to the negative pressure isolation ward for isolation control; EBOV can be infected by contacting the blood and other body fluids, vomit, secretions and excrements of infected patients or animals, and cut off these The route of transmission can effectively prevent EBOV infection. The "Ebola Hemorrhagic Fever Prevention and Control Plan (Second Edition)" issued by the National Health and Family Planning Commission on August 15, 2014 provides detailed information on the tracking and management of personnel from epidemic areas, the management of close contacts, and the transfer and isolation of patients. Regulations and clearly stated that pathogenic experiments such as virus isolation and culture, animal infection experiments, antigen-antibody and nucleic acid detection should be carried out in BSL-4/BSL-3 laboratories; issued by the National Health and Family Planning Commission on September 2, 2014 The "Ebola Hemorrhagic Fever Hospital Infection Prevention and Control Technical Guidelines (First Edition)" detailed the diagnosis and treatment of EVD patients in hospitals, the management of close contacts, the protection of medical staff, and the prevention and control of hospital infections. Regulations.

　　Nine, outlook WHO announced the end of the EVD epidemic in Nigeria on October 20, 2014. In this epidemic, a total of 19 EVD patients were diagnosed in Nigeria, of which 7 died. The case fatality rate is 40%, which is much lower than the 70% case fatality rate in other places, indicating the spread of EBOV Can be contained. However, there are still many problems to be solved for EVD: ①The natural host and the intermediate host are not very clear; ②The circulation mode of EBOV in nature is not clear; ③How EBOV down-regulates immune response, how to mediate lymphocyte apoptosis and how to damage antigen Pathogenic mechanisms such as the ability of presenting cells to process antigens are still unclear; ④Current vaccine research is mainly limited to Zaire-type EBOV, and other types of research are lacking; ⑤Vaccines and effective antiviral drugs are still in the preclinical or I phase Clinical trial stage; ⑥The epidemic is spreading from Africa to Europe and America. In addition, due to the long incubation period of EBOV, most of the infected travelers do not show symptoms, and may not even know that they have been infected. For this part of patients, body temperature detectors and other intervention methods are both used when leaving the country or in the environment. Unable to find them, it is difficult to isolate them as soon as possible. In short, there is still a long way to go to completely defeat EBOV.