Recently, when most countries in the world are still struggling with the COVID-19, the Ebola virus (EBOV) that is more deadly, resurfaced.

According to UN News, a funeral was held on February 1 after the death of a nurse in southern Guinea, West Africa, on January 28. Unfortunately, the 6 people who attended the funeral developed diarrhea, vomiting, bleeding, and fever a few days later, and two of them died. Later, 8 people were infected and 3 people died.

As the patients' symptoms resembled Ebola virus disease (EVD), the National Laboratory of Guinea made urgent sampling and analysis and finally determined that it was EBOV.

EBOV is a negative-strand RNA virus of the filoviridae family, which was firstly discovered in 1976 when two consecutive fatal hemorrhagic fever outbreaks occurred in various parts of Central Africa. The first outbreak occurred in Congo, a village near the Ebola River, and therefore the virus was named Ebola. The second outbreak occurred in South Sudan, which is about 850 kilometers away.

Since its first appearance, the virus has not been extinct for decades, and once caused severe damage to many countries in Africa. There were four outbreaks in Sudan, with an average death rate of 53.76%. There have been five Ebola outbreaks in Congo. As of April 14, 2020, 29 health districts had reported 3458 cases, with an average mortality rate of 66%.

In May 2020, a study called "Ebola" was published in The New England Journal of Medicine, which provides detailed explanations for a better understanding of the Ebola outbreak.

The virus initially infects humans through direct contact with animal blood, body fluids, and tissues, and then spreads to other people through the body fluids of EVD patients. The incubation period of EBOV is the time interval from viral infection to the onset of symptoms, which can last from 2 to 21 days. Infected people become infectious only after they develop symptoms that mainly include fever, fatigue, muscle pain, headache, sore throat, and then vomiting, diarrhea, skin rash, impaired kidney and liver function, or bleeding. After the patient recovers, fatigue, muscle aches, eye and vision problems, and stomach pains still occur.

A study previously published in The Lancet showed that regardless of the disease severity, EBOV often persists in the eyes, central nervous system, testes, and other human immunologically privileged parts, in which the antiviral immune response is less effective against the virus. Persistence is related to clinical sequelae, disease reactivation, long-term virus shedding, and virus transmission, which indicates a delay in virus clearance and an increased risk of re-spreading where the original outbreak is under control.

Studies showed that in the acute and recovery phases of the disease, after the RT-PCR test in the blood turns negative, the viral RNA can be detected in other body fluids, such as saliva, tears, sweat, breast milk, urine, eye fluid, amniotic fluid, vaginal fluid, and semen. The semen of cured male patients will still be positive for RT-PCR test for several months to several years after being discharged from the hospital, and the viral RNA concentration dropped by 4 times every month. The virus discovered in semen was still contagious for more than a year after the onset of the disease.

EBOV is a biosafety level 4 (BSL-4) organism, which refers to the highest level of safety isolation grading when separating and testing microbial tissue structures in the laboratory. HIV and the SARS-COV-2 belong to the third level. The diseases caused by the BSL-4 organisms in humans are incurable in most cases.

Global emergency supply of Ebola vaccine
In November 2019, the Ervebo produced by Merck obtained marketing authorization in the European Union, becoming the world's first Ebola vaccine officially approved for marketing. Another experimental Ebola vaccine developed by JNJ was also tested in the severely affected provinces of Congo in the same year. WHO, UNICEF, IFRC, and other organizations jointly announced on January 11, 2021, the establishment of a global Ebola vaccine stockpile, which can be quickly mobilized once the epidemic breaks out again in the future to immunize high-risk groups to curb the spread of the virus.

The first FDA approved treatment for Ebola virus
Regeneron's Inmazeb (atoltivimab, maftivimab, and odesivimab-ebgn), a mixture of three monoclonal antibodies, was approved by the FDA on October 14, 2020, which was the first FDA-approved treatment for Zaire ebolavirus (Ebola virus) infection in adult and pediatric patients.

Inmazeb targets EBOV GP (Ebola virus glycoprotein: on the surface, which attaches to the cell receptor, fuse the virus and the host cell membrane, allowing the virus to enter the cell. The three antibodies that make up Inmazeb can bind to the glycoprotein at the same time and prevent the attachment and entry of the virus. Common adverse reactions when taking Inmazeb include fever, chills, rapid heartbeat, shortness of breath, and vomiting, which are also common symptoms of EVD. The FDA pointed out that patients receiving Inmazeb should avoid simultaneous vaccination, because this treatment may inhibit the replication of the vaccine virus and may reduce the efficacy.

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