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Ebola virus is a highly contagious disease that can cause Ebola hemorrhagic fever in humans and primates. It was discovered in 1976 in the Ebola River region of southern Sudan and the Democratic Republic of Congo. It belongs to the family of filamentous viruses, with a single negative stranded RNA genome and polymorphic elongated filamentous viral particles with an envelope containing only one glycoprotein. The Ebola virus is divided into five subtypes: Zaire, Sudan, Bendibugyo, Ivory Coast, and Reston. It can grow in various cultured cells, with the most commonly used being Vero cells, MA-104 cells, etc. Its resistance is not strong and it is sensitive to ultraviolet radiation, lipid solvents, etc.
Figure 1. Ebola Virus.( Nguyen, Van Kinh, et al.2015)
The Ebola virus is mainly transmitted through close contact. Fruit bats, as natural hosts, transmit the virus to wild animals such as chimpanzees and monkeys. Humans become infected through contact with these animals and their bodily fluids, excreta, etc., and become a source of infection. The virus invades the host through the skin and mucous membranes, mainly proliferating in the liver, causing damage to vascular endothelial cells, leading to tissue cell lysis, organ necrosis, and so on. The release of inflammatory mediators such as IFN - γ by monocytes macrophages is the main cause of increased capillary permeability and rash.
Ebola virus (EBoV) belongs to the family of filamentous viruses, with a length of 970 nanometers and a long filamentous body. Externally enveloped, the virus particles have a diameter of approximately 80 nanometers and a size of 100 nanometers by (300-1500) nanometers. Viruses with strong infectivity are generally about 665-805 nanometers long and can be branched, U-shaped, hexagonal, or ring-shaped, with branched shapes being more common. There is a capsule with 8-10 nanometer long spikes on the surface. Pure virus particles consist of a helical ribonucleocapsid complex, containing negative linear RNA molecules and four viral structural proteins. The longer and peculiar virus particle related structures can be branched or coiled, up to 10 micrometers in length. The Ebola strains from the Democratic Republic of Congo, Ivory Coast, and Sudan have different antigenicity and biological characteristics.
The Ebola virus recognizes host cell surface receptors (such as NPC1 and Niemann Pick C1 proteins) through surface glycoprotein GP (divided into GP1 and GP2 subunits), and binds to co receptors such as TIM-1 and DC-SIGN to mediate the fusion of the virus envelope and cell membrane, releasing the nucleocapsid into the cytoplasm. Subsequently, the virus utilizes L polymerase (which binds to NP, VP35, VP30 to form a replication complex) to initiate RNA replication: first synthesizing positive stranded RNA (as a template), and then synthesizing new negative stranded genomic RNA based on positive stranded RNA. At the same time, the virus protein is translated and finally assembled into mature virus particles, which are released through VP40 mediated budding and continue to infect surrounding cells.
The Ebola virus has been classified into five subtypes, namely EBO Zaire, EBO Sudan, EBO-R, EBO-CI, and Reston. Different subtypes have different characteristics, and EBO-Z and EBO-S have high pathogenicity and mortality rates in both human and non-human primates. EBO-R is not pathogenic to humans and has lethal effects on non-human primates. EBO-CI has significant pathogenicity to humans, but generally does not cause death, with a high mortality rate for chimpanzees.
The Ebola virus is a highly dangerous pathogen that must be isolated and identified in specialized experimental facilities. In African epidemic areas, diagnosis is mainly made by testing for specific IgM and IgG antibodies against Ebola virus, as well as by examining virus antigens or nucleic acids.
| Inspection Method | Details |
| Testing for Virus Specific Antibodies | The virus specific IgM antibodies in the patient's blood appear 2-9 days after onset and persist until 1-6 months after onset. IgG antibodies appear 6-18 days after onset and persist for more than 2 years. The ELISA method for detecting Ebola virus IgG antibodies was established using the carboxyl terminal peptide of the virus core protein prepared by genetic engineering as the antigen, with high specificity and sensitivity. However, for patients with low specific antibody titers in the acute phase serum, virus antigen or nucleic acid testing should be performed simultaneously. |
| Testing For Virus Specific Antigens and Nucleic Acids | It has been confirmed that the consistency between detecting Ebola virus antigen and detecting virus nucleic acid is almost 100%, with high sensitivity. Moreover, after irradiating the specimen with gamma rays and inactivating the virus, the safety of the experiment increases when detecting virus antigens or RNA, and the experimental results are not significantly affected. |
Ebola hemorrhagic fever has mainly manifested as a local epidemic, limited to the rainforests of Central Africa and the tropical savannas of Southeast Africa, but has expanded from Sudan and the Democratic Republic of Congo to the Republic of Congo, the Central African Republic, Libya, Gabon, Nigeria, , Cameroon, Zimbabwe, Uganda, Ethiopia, and South Africa. Occasional cases have been reported outside of Africa, all of which are imported or laboratory acquired infections, and no outbreaks of Ebola hemorrhagic fever have been found. The Ebola virus only intermittently spreads in a few countries and regions, and has certain limitations in time and space.
To control the spread of Ebola, we must first closely monitor the dynamics of the global Ebola virus epidemic, strengthen border quarantine, suspend the import of monkeys, and mainly restrict monkeys from epidemic areas. So far, no animals other than primates have been found to be hosts of Ebola virus. Suspected patients with bleeding symptoms should be isolated and observed. Once diagnosed, the patient should be promptly reported to the health department and subjected to the strictest possible isolation, using isolation equipment with air filtration devices. Medical staff and laboratory personnel should wear isolation suits and, if possible, space suits for inspection operations to prevent accidents. Close observation should also be conducted on those who have close contact with the patient.
The treatment is primarily auxiliary, including minimizing virus invasion, balancing electrolytes, repairing lost platelets to prevent bleeding, maintaining oxygen levels in the blood, and treating complications. Excluding individual cases, the serum of Ebola recovered individuals has little effect in treating the disease. Interferon is also ineffective against Ebola. In monkey experiments, coagulation interferon seemed to have some effect, allowing 33% of infected monkeys that were originally 100% dead to survive. There is currently no specific treatment for Ebola virus disease, and some antiviral drugs such as interferon and ribavirin are ineffective. The main treatment is supportive and symptomatic, including paying attention to water and electrolyte balance, and controlling bleeding. Dialysis treatment is performed during renal failure.
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