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Ebola Virus Disease

Dr. Ajay Mohan (AIIMS)MBBS

May 05, 2020

May 05, 2020

Ebola Virus Disease
Ebola Virus Disease

Ebola virus disease is a rare, but lethal viral infection. It is caused by the Ebola virus, one of seven filoviruses that can affect humans (Marburg virus is also a type of filovirus that affects humans). In the past, mortality rates for Ebola virus disease have varied between 25% and 90%, averaging at around 50%.

The virus was first seen in 1976 in two separate outbreaks in Zaire (now the Democratic Republic of the Congo or DRC) and Sudan. It was named after the Ebola river in Zaire, where a cluster of cases was originally found. Outbreaks since then have been mainly in the Central African region and have not spread too readily.

In 2013, the largest outbreak of Ebola virus disease so far originated in western Africa’s Guinea and broke the patterns seen in the past. The disease jumped international borders to other western African countries, leading to over 28,000 infections and 11,325 deaths. The epidemic was only contained three years later in 2016.

In August 2018, when another outbreak started in the DRC, relief efforts got mired in regional conflict and isolated cases are still emerging: cases were reported from Beni in the DRC as recently as 10 April 2020.

Outside the African continent, outbreaks have been contained, with only a handful of cases reported. However, Ebola remains a global health threat given its virulence and our connectedness in a globalized world.

While the exact origins of the virus are unknown, genetic evidence suggests that fruit bats or non-human primates such as gorillas and chimpanzees may be involved. The disease can be transmitted to humans from infected animals in what is known as a "spillover event", by coming in contact with infected fluids or ingestion of contaminated meat. 

Ebola virus can also spread via direct contact with the blood and other bodily fluids of an infected person—including their semen, saliva, sweat, urine and breast milk. Contaminated fomites (things multiple people may have touched and used, like lift buttons) indirectly spread the disease as well. Airborne transmission has not been reported. The virus can only be transmitted after the person begins showing symptoms; the incubation period is eight to 10 days. 

Symptoms are initially fever, body aches and pains and fatigue. These are followed by diarrhoea (sometimes bloody) and vomiting, bleeding and bruising

Treatment is focused on managing the symptoms; fluid replacement therapy, supplemental oxygen are provided and opportunistic infections are taken care of. (Read more: What is oxygen therapy?)

During the latest outbreak in the DRC, monoclonal antibody therapy with two antiviral drugs, Regeneron (REGN-EB3) and mAb114, showed promising results. The vaccine rVSV-ZEBOV has also shown promise against the Zaire Ebola virus strain; it is being administered to at-risk populations.

How does Ebola Virus spread?

The virus jumps from animals to humans in a "spillover event". This is usually caused by direct contact with the bodily fluids of an infected animal such as a fruit bat or non-human primate.

Human to human transmission can occur by coming in contact with blood or bodily fluids such as sweat, urine, faeces, vomit from an infected person, or indirectly via fomites. 

As mentioned above, only those patients who are symptomatic can spread the virus.

Ebola can also be transmitted sexually, though this is rare. The virus can live in semen for long periods of time, so males who recover from the disease must get tested after recovery before having sex.

Ebola can also be transferred in-utero and has been associated with larger numbers of miscarriages and stillbirths. The virus has been found in breast milk as well, so infected mothers need to follow careful guidelines about nursing their babies. 

Once the body clears the virus, immunity to that strain of Ebola is developed. According to the latest research, immunity may last 10 years. However, this is an estimate and further research is needed to understand if the immunity is partial or complete. 

Relapses after recovery have been documented, but they are rare.

Ebola virus disease symptoms

Symptoms begin to show after eight to 10 days of infection on average. Initially, after 1-3 days of disease onset, the symptoms include:

They progress to more serious symptoms:

  • Nausea
  • High volumes of vomit and diarrhoea 
  • Bleeding and haemorrhaging 
  • Neurological symptoms such as meningoencephalitis (inflammation of the brain and the meninges or membrane around it), seizures, and coma

Since symptoms have an overlap with generalized viral infections at least initially, diagnostic testing is required to confirm the disease.

Asymptomatic cases of Ebola have been reported but they are rare.

Mortality rate progresses linearly by age and peaks at 35-44 years. Fewer cases in children have been reported, but this may be due to the fact that preventive measures are stronger; children have been kept away from infected people and are not usually responsible for providing care in the household setting.

Having said that, evidence suggests that the disease is more virulent in children; incubation times are shorter and children below the age of 5 have been found to be most susceptible to the virus.

Ebola is such a deadly virus because it directly attacks the immune system. It kills off guard cells known as macrophages and causes dendritic cells—which help coordinate immune responses—to go haywire. This results in a compromised immune response which eventually leads to a cytokine storm wherein the immune system ends up damaging vital organs.

 

Prevention of Ebola virus disease

There are at least two reasons why Ebola has not managed to spread as widely and as quickly as, say, COVID-19 (the viral infection behind the 2019-20 pandemic):

  • First, droplet transmission is not possible in Ebola.
  • Second, only symptomatic Ebola patients are contagious.

This has helped plan containment and prevention strategies. 

Effective preventive programmes consist of:

  • Community mobilization and spreading awareness about the disease.
  • Case management, including monitoring of those infected and contact tracing.
  • Robust health facilities and healthcare providers, diagnostic labs and safe burials. 

Other recommendations include: 

  • Thoroughly washing hands at regular intervals if an outbreak zone.
  • Wearing gloves and protective clothing when engaging with wildlife, and thoroughly cooking meat before consuming it.
  • Burials should be conducted safely and with dignity. In past outbreaks, burials have been the sites of infections as bodily fluids get transferred when handling the bodies. Therefore, specialized burial teams must conduct these rituals when an Ebola patient passes away.
  • Safe sex practices go a long way in stemming infections. Since Ebola can survive in semen for long periods of time, condoms must be used for at least a year after recovery or after two tests come back negative.

Diagnosis of Ebola virus disease

As discussed earlier, initial symptoms are generalized. Diagnosing the virus soon after infection is, therefore, tricky. Testing is undertaken if there has been suspected contact with an infected person or wildlife. Testing is rushed if initial symptoms develop in an endemic area. Blood samples are collected, or oral samples (saliva) are taken if blood is not an option, and the following diagnostic methods may be used depending on availability:

Ebola virus disease treatment

There is currently no proven treatment for Ebola. However, early detection and intervention have been shown to improve the prognosis. Fluid replacement therapy, supplemental oxygen and treating opportunistic infections are invaluable, as they can buy the body some time to mount an effective immune response. 

As mentioned above, two antiviral drugs and the vaccine rVSV-ZEBOV have shown encouraging signs and have been deployed in the latest outbreak in the DRC.

Having said that, Ebola is one of the deadliest known viruses, and providing adequate healthcare in resource-poor regions can be a huge challenge. Prevention is, therefore, the superior method of combating the virus.

Life after Ebola virus disease

Those who survive Ebola are likely to develop some sort of immunity to the strain of the virus that infected them. However, long-term health and social issues can persist. These include:

Ebola is still a relatively new virus and has many unknowns. Counselling services and regular health checkups are recommended for survivors; the virus can persist in certain parts of the body that may interfere with everyday life.

While the ongoing outbreak has caused a lot of misery, it has also armed us with a wealth of information and some drugs that seem to work against the virus. Hopefully, these hard earned lessons will eventually contain a virus that has seemed unstoppable in the past.



References

  1. Shevin Jacob, et al. Ebola Virus disease. Nat Rev Dis Primers 6, 13 (2020). PMID: 32080199.
  2. Sarathi Kalra, et al. The Emergence of Ebola as a Global Health Security Threat: From ‘Lessons Learned’ to Coordinated Multilateral Containment Efforts. J Glob Infect Dis. 2014 Oct-Dec; 6(4): 164–177. PMID: 25538455.
  3. Mahmoud Tawfik Khalafallah, et al. Ebola virus disease: Essential clinical knowledge Avicenna J Med. 2017 Jul-Sep; 7(3): 96–102. PMID: 28791241
  4. CDC [Internet]. Centers for Disease Control and Prevention; Ebola (Ebola Virus Disease)
  5. WHO [Internet]. World Health Organization; Pregnancy and breastfeeding during an Ebola virus outbreak
  6. WHO [Internet]. World Health Organization; Democratic Republic of the Congo begins first-ever multi-drug Ebola trial

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