Ebola : one epidemic after another

Abstract

The first known epidemic linked to the Ebola virus dates back to 1976. It occurred at a time when infectious diseases were thought to have been conquered, at least in industrialized countries, thanks to advances in hygiene, antibiotics and vaccines. Ebola, followed by AIDS a few years later, showed us that we still have infectious diseases to contend with : thus the concept of emerging diseases was born. The Ebola virus is a particularly frightening disease, with its hemorrhagic fever-like clinical manifestations and very high mortality rate. What's more, healthcare workers are highly exposed to the risk of contracting the disease.

The investigation of the first epidemic of Yambuku in Zaire was successful : the virus was identified for the first time ; the clinical course of the disease and the role of injections and interpersonal contact in the transmission of the virus were described ; control measures combining surveillance, isolation and quarantine were put in place, as well as the use of protective equipment, decontamination of infected surfaces and management of corpses. Finally, the first transfusions of convalescent plasma will be tested. More than 20 epidemics have occurred since then, all in Central Africa, except for one in West Africa (2014-2015), the largest, with more than 25 000 cases and 11 500 deaths. Clinical and epidemiological knowledge of the disease is improving.

We learn that patients can excrete the virus in their semen several months after recovery, and thus be the source of a new outbreak. Above all, we understand that the response to the epidemic must be adapted to local customs and beliefs, and the concept of safe, dignified burial, respecting funeral rites, is put in place. The search for an animal reservoir led to the identification of antibodies and viral nucleotide sequences in fruit bats from Central Africa. Great apes and antelopes play the role of intermediate hosts, enabling transmission of the virus to humans. It was not until the West African epidemic in 2014-2015 that significant progress was made in evaluating biomedical response tools. A vaccine trial in Guinea has demonstrated the efficacy of a live attenuated recombinant vaccine, which is administered to patient contacts using a " ring " strategy.

As for treatments, monoclonal antibodies seem promising, but trials carried out in a difficult context lack the statistical power to demonstrate their efficacy. The outbreak of a new epidemic in North Kivu in 2018, reaching urban centers with more than million inhabitants, and in a context of armed conflict and mistrust of healthcare personnel by the population, raises fears of the epidemic moving to an endemic stage where elimination of the virus will become extremely complex.