Ebola Virus Disease (EVD)

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Introduction

Ebola virus disease (EVD) is a serious illness caused by the Ebola virus, belonging to the family of viruses known as Filoviridae that affects both humans and other primates. The Ebola virus is a non-segmented, linear, single-negative-stranded RNA virus. Ebola is a virus that damages tissue throughout the body and causes severe inflammation. A single-stranded RNA flavivirus that tends to replicate on dendritic cells, macrophages, and monocytes is responsible for the sickness. Most viruses that cause EVD are found primarily in sub-Saharan Africa.

Although the Ebola virus cannot be spread through the air, it is generally not thought to be contagious before symptoms appear.
Direct contact with the organs, blood, secretions, or other bodily fluids of infected individuals, animals, or their corpses is necessary for transmission.
The Ebola virus frequently causes vague symptoms that, at first, may resemble those of more widespread illnesses, but depending on the virus type and quality of supportive treatment provided, may cause a high fatality rate.
The virus is referred to as a hemorrhagic fever because it can interfere with the body’s clotting system and cause internal bleeding as blood seeps from tiny blood vessels.
Ebola has earned a reputation as one of the worst viral zoonotic illnesses of humans due to its high case fatality rates.
Person-to-person transmission depends on close personal contact with a patient’s bodily secretions, whether they are still alive or have passed away.
As a result, if strict infection prevention and control measures are taken, the risk of infection is thought to be very low.

Incidence

When two consecutive epidemics of deadly hemorrhagic fever occurred in various regions of Central Africa in 1976, EVD, one of the deadliest viral diseases, was identified.
The second outbreak, which happened around 500 miles (850 km) downstream, happened in what is now South Sudan.
On May 8, 2018, the Democratic Republic of the Congo (DRC) proclaimed a new EVD outbreak after two further cases were confirmed by a lab.
There had recently been 21 people reported in the nation with hemorrhagic fever symptoms, 17 of whom had passed away before the outbreak was officially confirmed.
As of September 17, 2019, there were 3,034 confirmed cases and 111 probable cases, with 2,103 deaths associated with EVD.
The large Ebola virus outbreak from 2014 to 2016 predominantly affected Sierra Leone, Guinea, and Liberia.

Incubation Period of the Ebola Virus

At the time of exposure, until symptoms or signs occur, the incubation period for Ebola can last anywhere between 2 and 21 days, 8 to 10 days on average.
Before showing symptoms, an Ebola patient cannot transmit the illness.

Classification of the Ebola Virus

The five Ebola virus species were given their names after the places where they were known to have infected people or animals.

Sudan Ebola virus and Zaire Ebola virus: The majority of reported fatalities have been attributed to two African species, Sudan ebolavirus and Zaire ebolavirus (both of which are among the deadliest Ebola virus species).
Ivory Coast Ebola virus: Except for one patient who survived infection with a third African species, Ivory Coast ebolavirus, clinical sickness caused by the African-derived Ebola virus is severe and is associated with a fatality rate ranging from 65% (Sudan, 1979) to 89%. (Democratic Republic of the Congo [DRC], December 2002 to April 2003).
Reston Ebolavirus: A remarkably identical isolate imported from the same Filipino exporter was discovered in Siena, Italy, in 1992. Reston ebolavirus, a fourth Ebolavirus species, was originally discovered in monkeys imported from a single Philippine exporter in 1989.
Bundibugyo Ebolavirus: The fifth Ebolavirus species, Bundibugyo ebolavirus, which is likewise of African ancestry, caused an outbreak in Uganda in 2007–2008 with a fatality rate of 25%.

Causes of Ebola Virus Disease

It is caused by the Ebola virus, belonging to the family of viruses known as Filoviridae, the genus Ebolavirus.
The Ebola virus infects a person through contact with an infected animal, like a fruit bat or nonhuman primate.
The virus travels from person to person, possibly impacting a huge number of people.

Risk Factors of Ebola Virus Disease

Risk factors for EVD include:

Family members and friends who come into close contact with Ebola patients.
Healthcare staff who do not practice infection control measures effectively while caring for EVD patients are most at risk of getting the disease.
When an individual comes in contact with infected body fluid or blood.
Handling potentially infectious wild animals or carcasses (such as monkeys, fruit bats, or duikers)
Engaging in sexual activity with a man whose EVD has been treated.
Visiting regions of Africa where Ebola cases have been confirmed.
Using imported monkeys from the Philippines or Africa for animal studies.
Preparing those who have contracted Ebola for burial.

Mode of Transmission of Ebola Virus Disease

Human-to-human transmission of Ebola can happen by:

Contaminated body fluids: Blood or body fluids (urine, saliva, perspiration, feces, vomit, breast milk, and semen) of an individual who has the Ebola virus disease or has passed away from it (EVD).
Contaminated substances: Objects that have been contaminated with body fluids from a person who has EVD or has died from it, including clothing, bedding, needles, and medical equipment.
Vectors: Fruit bats or non-human primates with the disease (such as apes and monkeys)
Infected semen: Sperm from a man who overcame EVD (through oral, vaginal, or anal sex). The virus can remain in some body fluids (including sperm) even after an EVD patient no longer experiences severe symptoms.
During burial ceremonies where mourners come into physical contact with the corpse of the deceased.

Signs and Symptoms of Ebola Virus Disease

Ebola virus disease has also the same symptoms in many cases as other common illnesses such as influenza, malaria, or typhoid fever.

Early Stage

Stomach Aches
Anorexia (loss of appetite)
Arthralgia (joint pain)
Asthenia (lack of energy and strength)
Back pain
Exhaustion
Fever (over 37.50C)
Headache
Myalgia (muscle pain)
Sore throat
Diarrhea and vomiting

Mid Stage

Capillary leak
Confusion
Respiratory discomfort
Headache
Low blood pressure
Dizziness
Nausea and vomiting;
Rash (maculopapular)

Late Stage

Multi-organ failure
Shock
Delirium
External or internal bleeding
Hiccups
Shock (hypovolemic and septic)
Although they are uncommon, encephalopathy, hepatomegaly, lymphadenopathy, and seizures are further signs of EVD.

Pathophysiology of Ebola Virus Disease

Ebola virus enters a person through mucosal membranes, cracks in the skin, or parenterally.
Many different cell types, including monocytes, macrophages, dendritic cells, endothelial cells, fibroblasts, hepatocytes, adrenal cortical cells, and epithelial cells, are infected by ebolaviruses.
According to the infection route, the incubation period may be affected.
The liver, spleen, and adrenal gland are the next organs that the ebolaviruses reach after infecting the first site of infection.
Lymphocytes undergo apoptosis, which lowers lymphocyte counts even when they are not infected with an ebolavirus.
Dysregulation of the clotting factors leads to coagulopathy and hepatocellular necrosis, which both occur together.
There is a possibility of adrenocortical necrosis, which is connected to hypotension and a problem with steroid synthesis.
Pro-inflammatory cytokines seem to be released by ebolaviruses, and this is thought to cause vascular leakage and clotting dysfunction, which ultimately lead to multi-organ failure and shock.

Diagnosis of Ebola Virus Disease

History

Primary and secondary exposure histories are recognized in patients with Ebola virus infection.
A history of primary exposure typically involves travel to or employment in an Ebola-endemic region.
Secondary exposure is defined as human-to-human or primate-to-human exposures.

Physical examination

Physical findings depend on the stage of the illness at the time of presentation.
Early in the illness, patients may present with fever, pharyngitis, and severe constitutional symptoms.

Regular blood testing

Thrombocytopenia, leukopenia, and noticeable lymphopenia are symptoms of infection that appear early on.
When a few days pass, neutrophilia also appears, along with elevations in aspartate aminotransferase and alanine aminotransferase. Bilirubin levels may be normal or slightly raised.

Polymerase chain reaction (PCR)

Because it can identify very low concentrations of the Ebola virus, polymerase chain reaction (PCR) is one of the most widely used diagnostic techniques.

Virus isolation research

A reverse transcription polymerase chain reaction (RT-PCR) assay or tissue culture virus isolation is required for a conclusive diagnosis.

IgM-capture ELISA

To identify IgM antibodies to this strain, ELISA analyses Zaire ebolavirus antigens produced in Vero E6 cells.
Within six days of infection, the results in experimental primates turn positive, but they do not hold positive for very long.

IgG-capture ELISA

To find IgG anti-Ebola antibodies, an ELISA assay extracts viral antigens using detergent.
Compared to the IFAT, it is more focused and sustainably positive.

Treatment/Management of Ebola Virus Disease

The majority of Ebola virus disease treatment is supportive because there is currently no cure.
The suggested precautions are:

Volume repletion
Blood pressure management (with vasopressors if needed).
Treatment of subsequent bacterial infections and pre-existing comorbidities.
Maintenance of oxygenation.
Pain management.
Nutritional support.
Convalescent serum: The liquid portion of their blood, known as serum, is extracted from an individual who is recovering from the disease. The extracted serum (which may have antibodies against the Ebola virus) will be transfused to the Ebola virus disease patient to treat it.
Medications- The U.S. Food and Drug Administration (FDA) has currently approved two medications to treat EVD in both adults and children that are brought on by the Zaire Ebola virus, a species of the Ebola virus.
- Inmazeb, which combines three monoclonal antibodies (atoltivimab, maftivimab, and odesivimab-ebgn), will be the first medication authorized in October 2020.
- Ebanga, the second medication, was authorized in December 2020 and is a single monoclonal antibody.

Complications of Ebola Virus Disease

Different immune systems can react differently to the Ebola virus. Others may experience lasting symptoms, even though some may fully recover from the illness. Some of these aftereffects include:

Joint conditions
Hair loss
Acute exhaustion and weakness
Psychosis
Inflammation of the eyes and liver
Sensory alterations
Suppurative parotitis
Asymmetric and migrating arthralgias
Headache
Bulimia
Amenorrhea
Hearing loss
Tinnitus
Jaundice.

Prevention of Ebola Virus Disease

There are several measures to safeguard oneself and stop the spread of the Ebola virus when residing in or visiting a place where ebolaviruses may be present.

Vaccination

The Ebola vaccine, ERVEBO® (a single-dose vaccine), has been given the FDA’s approval to be used in the fight against the disease.
The Zaire ebolavirus species (responsible for Ebola outbreaks to date) is the only one against which the ERVEBO vaccine is safe and effective.
A pre-exposure prophylaxis against the Zaire ebolavirus is also available for adults ≥18 years of age.

Other preventive measures

Steer clear of ill people’s blood and body fluids, including their urine, feces, saliva, sweat, vomit, breast milk, amniotic fluid, semen, and vaginal secretions.
Until testing demonstrates that a man’s semen is free of the Ebola virus, avoid coming into contact with it or use a condom while having sex.
Clear objects that may have come into contact with body fluids or blood from an infected individual (such as clothes, bedding, needles, and medical equipment).
Abstain from touching a deceased person’s body during a funeral or burial if they are known or suspected to have had Ebola.
Keep your distance from bats, woodland antelopes, non-human primates (such as monkeys and chimps), and anything cooked with the blood, fluids, or raw meat of these or other animals.
Cleaning the residences of Ebola patients with bleach and hospital-grade disinfectants can destroy and sterilize them.
Isolating those who are Ebola-positive.
Adopting infection-control measures, such as thorough equipment sterilization and routine use of disinfectants; making sure all healthcare personnel wears protective clothing.
Handling all animals and their waste with gloves and other protective clothes.
Regular hand washing.
Wearing protective gear like gloves and other personal protective equipment (such as face protection and long-sleeved gowns) when dealing with infected patients;

Prognosis

The prognosis for Ebola virus disease is frequently poor.
The mortality rate for this illness ranges from 25% to 100%.
Those who survive could endure the sequelae.
The recovery of EVD depends on early action, availability of quality medical treatment, delivery of ongoing supportive care, and frequent patient reassessment.
The majority of epidemics have occurred in places with few resources and supportive treatment, hence, the case fatality rate in other places may be about 40%.
The Zaire ebolavirus is the deadliest species, with a case fatality rate of up to 90%.
At most treatment facilities during the West African outbreak of 2014, the average case fatality rate was over 50%; however, rates in various prior outbreaks ranged from 25% to 90%.
Compared to adolescents and younger adults, the death rate is higher for younger children (under the age of 5) and individuals over the age of 40.
Infection frequently results in death in pregnant women, who experience a high rate of miscarriage.

Summary

Ebola Virus disease is a fatal illness that affects both humans and nonhuman primates.
Humans and nonhuman primates that have contracted an infection go through a brief phase of fast viral multiplication that, in certain fatal circumstances, is accompanied by an inadequate immune response.
Ebola virus infection occurs when a person comes into contact with an infected animal, such as a fruit bat or nonhuman primate.
The virus spreads from person to person and may affect a sizable population.
Fever, headache, muscle aches, sore throat, overall unease, abdominal pain, diarrhea, vomiting, and blood loss are some of the symptoms (in some cases).
Death occurs as a result of an infection in 25% to 90% of cases.
Simple measures like oxygen therapy, fluid and electrolyte replacement, and medicine can greatly increase the likelihood of survival.
To prevent this, risky activities must be avoided.

References

Patel, PR., Shah, Su. (2023, Jan). Ebola Virus. StatPearls Publishing. Retrieved on 2023, March 31 from https://www.ncbi.nlm.nih.gov/books/NBK560579/
Jacob, S. T., Crozier, I., Fischer, W. A., 2nd, Hewlett, A., Kraft, C. S., Vega, M. A., Soka, M. J., Wahl, V., Griffiths, A., Bollinger, L., & Kuhn, J. H. (2020). Ebola virus disease. Nature reviews. Disease primers, 6(1), 13. https://doi.org/10.1038/s41572-020-0147-3
Di Paola, N., Sanchez-Lockhart, M., Zeng, X., Kuhn, J. H., & Palacios, G. (2020). Viral genomics in Ebola virus research. Nature reviews. Microbiology, 18(7), 365–378. https://doi.org/10.1038/s41579-020-0354-7
Malvy, D., McElroy, A. K., de Clerck, H., Günther, S., & van Griensven, J. (2019). Ebola virus disease. Lancet (London, England), 393(10174), 936–948. https://doi.org/10.1016/S0140-6736(18)33132-5
Trad, M. A., Naughton, W., Yeung, A., Mazlin, L., O’sullivan, M., Gilroy, N., Fisher, D. A., & Stuart, R. L. (2017). Ebola virus disease: An update on current prevention and management strategies. Journal of clinical virology: the official publication of the Pan American Society for Clinical Virology, 86, 5–13. https://doi.org/10.1016/j.jcv.2016.11.005
Batra, S., Ochani, R. K., Diwan, M. N., Yasmin, F., Qureshi, S. S., Bhimani, S., Shaikh, S., Tariq, M. A., Ahmed Ashraf, M., Farooqi, H. A., & Dodani, S. K. (2020). Clinical aspects of Ebola virus disease: a review. Le infezioni in medicina, 28(2), 212–222.
Center for Disease Control and Prevention (2023, March 23). Ebola Disease. Retrieved on 20023, April 2 from https://www.cdc.gov/vhf/ebola/index.html