Pathology of Ebola Virus Disease

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Ebola virus causes acute hemorrhagic fever leading to up to 90% lethality.

The Ebolaviruses known to have five subtypes: Ebola virus (formerly known as Zaire virus), Sudan virus, Reston virus (non human), Tai Forest virus and Bundibugyo virus.

Of the five identified ebolavirus subtypes, four are capable of human-to-human transmission.

Recent study implicates "Fruit bats" as reservoir hosts for ebolaviruses.

Increasingly frequent outbreaks and the placement of Ebola virus in the category A list of potential biothreat agents have boosted interest in this virus.

The disease closely resembles Marburg Virus Disease.

Ebola Virus Disease has a high mortality.

Development of new technologies (Example: reverse genetics systems) and extensive studies on Ebola haemorrhagic fever in animal models have substantially expanded the knowledge on the pathogenic mechanisms that underlie this disease.

Two major factors in Ebola virus pathogenesis are the impairment of the immune response and vascular dysfunction.

The ebolaviruses appear to spread rapidly by close and prolonged contact with an infected person or by inoculation from contaminated syringes and needles.

Infected patients should be strictly isolated to prevent spread of ebolavirus infection.

Pathology :

Liver: The is necrosis of the hepatocytes, fatty change and presence of large intracytoplasmic eosinophilic inclusion bodies.

Adrenal glands: There is necrosis of adrenal cortical cells

Lymphnodes: Lymphnodes are enlarged. Necrosis of lymphoid follicles and medulla. There is infection of macrophages and dendritic cells causing depletion of host immune response.

Spleen : Necrosis of the red pulp.

History of past outbreaks:

Ebola virus infection was first recognized during a human outbreak in 1976 with almost simultaneous outbreaks in both the Sudan and Zaire (now the Democratic Republic of the Congo). It was named after a river in the Democratic Republic of the Congo.

After an outbreak in 1979 in the Sudan, Ebola appeared relatively quiescent until it appeared among macaque monkeys imported from the Philippines and housed at a primate facility in Reston, Virginia.

In late 1994, a single case in a researcher who performed a necropsy on an ill chimpanzee led to the identification of a new subtype, Ebola-Ivory Coast.

In Gabon, Africa, outbreaks of Ebola virus infection occurred from 1994 to 1997.

Another appearance was in 2000-2001 with an Ebola outbreak in Uganda that resulted in 425 cases with 224 deaths by January 2001. In this outbreak, events and conditions associated with acquired disease were : funeral attendance for those who died with Ebola hemorrhagic fever, intrafamilial contact, and nosocomial infections. Schools were closed and a ban against funerals was enacted. In November, 2001, an Ebola outbreak again occurred in Gabon. and in the Democratic Republic of the Congo, and multiple outbreaks occurred in 2000-2004 in Gabon, the Congo, Sudan, and Uganda.

Outbreaks continued in the Congo in 2005. At the same time, it was noted that Ebola outbreaks occurred in large mammals, mainly chimpanzees, duikers (a type of antelope), and gorillas, and that human outbreaks tended to follow those observed in animals. Airborne transmission of the Ebola Zaire strain to monkeys by aerosol have been demonstrated.

The deadly disease which has killed hundreds across West Africa (Guinea, Liberia and Sierra Leone) has also been reported in Lagos - Nigeria. (July 2014)

39 new cases and 21 deaths have been reported in Guinea between May and June 2014. In Sierra Leone 13 new cases have been reported during this same period. In Liberia 11 cases have been suspected and are being followed up.

Democratic Republic of Congo declared their tenth outbreak of Ebola in 40 years on 1 August 2018. The outbreak is centred in northeastern North Kivu province. With the number of cases surpassing 300, it is now the country's largest-ever Ebola outbreak.

Fruit bats as reservoirs of Ebola virus

Ebola virus vaccines: an overview of current approaches.

Phylogenetic Analysis of Guinea 2014 EBOV Ebolavirus

The 2014 Ebola virus disease outbreak in west Africa.