Where does the virus come from?

The Ebola virus was first identified in 1976 in the Democratic Republic of Congo (DRC, then Zaire).

This virus from the filoviridae family (filovirus) owes its name to a river in the north of the country, near which the first epidemic broke out.

Five distinct "subtypes" of the Ebola virus have since been identified: Zaire, Sudan (which is responsible for the death announced Tuesday in Uganda), Bundibugyo, Reston and Taï Forest.

The Zaire strain has been responsible for the vast majority of cases since 2014.

How is it transmitted?

The virus circulates among fruit-eating bats, considered the natural host of Ebola and which do not develop the disease.

Other mammals such as great apes, antelopes or porcupines can carry it and then transmit it to humans.

During an epidemic, Ebola is transmitted between humans through direct and close contact.

A healthy person is contaminated by the "bodily fluids" of a sick person: blood, vomit, faeces...

Unlike the flu, this virus is not transmitted through the air.

Ebola is therefore less contagious than many viral diseases.

But this virus is formidable because of its very high mortality rate: between 40% and 70% for example for the most recent epidemics in the DRC, according to the World Health Organization (WHO).

According to a study published in 2021 in the journal Nature, the virus could remain dormant in the body of survivors, before waking up years later, and thus being the cause of new outbreaks.

What symptoms?

After an incubation period of 2 to 21 days, Ebola is manifested by a sudden fever, with intense weakness, muscle and joint pain, headache and throat pain.

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These symptoms are followed by vomiting, diarrhea, skin rashes, kidney and liver damage, and in some cases, internal and external bleeding.

Sequelae are frequently observed in survivors: arthritis, vision problems, inflammation of the eye and hearing problems.

What treatments?

For the first time in August 2022, two monoclonal antibody treatments, strongly reducing the risk of death, were recommended by the WHO for people affected and newborns of sick mothers.

Several vaccines have been developed in parallel.

"Ring" vaccination campaigns consisting of vaccinating contacts of patients and contacts of contacts, obtained good results in 2021 in the DRC.

In 2021, vaccination associated with the use of the two drugs, for example, made it possible to slow down and then stop the spread of the virus in the Beni region, in the north-east of the DRC, according to the Congolese health authorities.

The worst epidemic (2013-2016)

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Starting in southern Guinea in December 2013, the most violent epidemic in the history of Ebola hit West Africa until 2016.

It claimed the lives of more than 11,300 people out of nearly 29,000 recorded cases, mainly in Liberia, Sierra Leone and Guinea.

The WHO declared the epidemic over in March 2016.

Numerous epidemic outbreaks in the DRC

The DRC has seen more than a dozen outbreaks since 1976, with a total death toll of more than 3,000, according to a compilation of WHO figures.

The most deadly Ebola epidemic in the DRC between 2018 and 2020 killed nearly 2,300 people for 3,500 sick people.

The most recent epidemic affected the northwest of this country from April 2022, killed five people and was declared over in July 2022 by the WHO.

As with recent outbreaks in this country, a vaccination campaign has been organized for contacts of patients as well as for "frontline" caregivers.

© 2022 AFP