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Ebolavirus Disease

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Synonyms: Ebolavirus disease, Ebola haemorrhagic fever.

Introduction: It is a contagious disease which is characterized by fever, headache, joint and muscle pain, weakness, diarrhoea, vomiting, stomach pain, anorexia, and abnormal bleeding.

Aetiology, morphology and geographical distribution: The first Ebola virus was discovered in 1976 near the Ebola River in Congo. Ebola disease is caused by a virus belonging to Filoviridae family. Tai Forest, Sudan, Zaire, Reston and Bundibugyo are the five identified species of ebolavirus. Ebola-Reston is the only known filovirus that does not cause severe disease in humans; however, it can still be fatal in monkeys and it has been recently recovered from infected swine in South-east Asia. 

In 1967, the disease was first time reported in (Marburg) Germany and Yugoslavia among laboratory workers. All of them were handling tissues from green monkeys. The disease, at that time was named as Marburg disease.

Morphologically it has several shapes like long, branched filaments, like a "6", a "U", or a circle. This biological feature is known as ‘pleomorphism’. Viral filaments may measure up to 14,000 nanometers in length, have a uniform diameter of 80 nanometers, and are enveloped in a lipid membrane. Each virion contains one molecule of single-stranded, negative-sense RNA. New viral particles are created by budding from the surface of their host’s cells; however, filovirus replication strategies are not completely understood.

Geographically it is distributed among the countries like Democratic Republic of the Congo, Gabon, South Sudan, Ivory Coast, Uganda, Republic of the Congo and South Africa. In 2014 Ebolavirus break is in West African countries viz. Guinea, Liberia, Sierra Leone and Nigeria.

Transmission of the disease: The natural reservoir of ebolavirus has not been proven yet. But researchers have hypothesized that the first patient becomes infected through contact with an infected animal. When virus enters the humans, the virus can be spread in several ways to others viz. direct contact with the blood or bodily fluids of an infected symptomatic person or though exposure to objects (such as needles) that have been contaminated with infected secretions.

It is not transmitted through the air. Similarly, it is also not a food-borne and water-borne disease.

Susceptibility: Healthcare workers and the family and friends in close contact with Ebola patients are at the highest risk of getting sick.

Epidemiology: In past Ebolavirus outbreaks have occurred in Democratic Republic of the Congo, Gabon, South Sudan, Ivory Coast, Uganda, Republic of the Congo and South Africa. In 2014 Ebolavirus break is in West African countries viz. Guinea, Liberia, Sierra Leone and Nigeria.

Immunity: Yet, there is no immunity against the disease.

Risk factors: The major risk factors include animals particularly the bats are considered the reservoir host of the ebolavirus. The virus is transmitted to non-human primates who may precede outbreaks in human beings. Among human beings it spread as mentioned earlier.

Pathogenesis: Initially infection shows nonspecific flu-like symptoms such as fever, myalgia, and malaise. As the disease advances, patients show severe bleeding and coagulation abnormalities, including gastrointestinal bleeding, rash, and a range of hematological irregularities, such as lymphopenia and neutrophilia. When reticuloendothelial cells encounters, release cytikinins, which can contribute to exaggerated inflammatory responses that are not protective. Damage to the liver, combined with massive viraemia, leads to disseminated intravascular coagulopathy. The virus eventually infects micro-vascular endothelial cells and compromises vascular integrity. The later stages of Ebola virus infection commonly include diffuse bleeding, and hypotensive shock accounts for many Ebola virus mortalities.

Clinical symptoms: The typical signs of the disease are fever (greater than 38.6°C or 101.5°F), severe headache, muscle pain, weakness, diarrhea, vomiting and colic, anorexia. But some patients may experience rash, red eyes, hiccups, cough, sore throat, chest pain, difficulty breathing, difficulty swallowing and unexplained bleeding inside and outside of the body.

Incubation period: 4 – 10 days is most common incubation period. However, it may take 2 to 21 days to develop the disease.

Course of disease: 14 to 21 days.

Post mortem lesions: Petechiae, ecchymoses and clear hemorrhages may be seen at the time of postmortem. Hemorrhages can occur in any organ, which are particularly common in the gastrointestinal tract, kidneys, and pleural, pericardial and peritoneal spaces. The friable hepatomegaly and spleenomegaly, and the liver may be severely reticulated and discolored. Other potential lesions include interstitial pneumonia, nephritis and a maculopapular rash, as well as necrosis of the liver, lymphoid tissue, adrenal cortex or pulmonary epithelium.

Diagnosis: At early stage ebola disease is difficult to diagnose. However, if suspected for the disease then the patient(s) should be isolated and public health professionals should be informed. The disease can be diagnosed symptomatically as well as laboratory tests like Antigen-capture enzyme-linked immunosorbent assay (ELISA) testing, IgM ELISA, Polymerase chain reaction (PCR), Virus isolation after few days of infection. IgM and IgG antibodies test can be performed during the course of disease or after recovery from the disease. Afterward the disease can be diagnosed in deceased patients with the help of Immuno-histochemistry testing, PCR and Virus isolation.

Treatment: There is no proven treatment against ebola disease. The treatment is only symptomatically which consists of balancing the patient’s fluids and electrolytes, maintaining their oxygen status and blood pressure and treating them for any complicating infections. However, if suspected patient is observed then the patient should be isolated and public health professionals notified.

Control/Prevention: No vaccine vaccine has been developed against ebolavirus. Whenever a case of ebola disease reported, the healthcare workers should be able to diagnose the disease at early stage so that disease can be prevented to spread further. The healthcare workers should wearing of protective clothing (such as masks, gloves, gowns, and goggles), using infection-control measures (such as complete equipment sterilization and routine use of disinfectant) and isolating patients with Ebola from contact with unprotected persons.

Quarantine measures: As the patient is suspected for the ebolavirus, then the patient(s) should be isolated and notified to the health professionals, immediately.

Zoonotic importance: Yet the natural reservoir of ebolavirus has not been proven. Howver, the animals particularly the bats are the natural reservoirs of the ebolavirus. Therefore, the disease has potent zoonotic importance.

 

References:

 

 

For more details and regular updates you may visit:

http://www.who.int/mediacentre/factsheets/fs103/en/

 

http://www.cdc.gov/vhf/ebola/

 

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