Can it spread in France? Lassa fever, a disease endemic to certain African countries, was detected in Île-de-France this Thursday, in a hospitalized soldier returning from abroad. His “state of health does not give rise to concern”, specified the Ministry of Health, which however specified that a “thorough epidemiological investigation is underway to determine the people who may have been in risky contact with the patient “.

Because Lassa fever, hemorrhagic like Ebola, is contagious. Detected in 1960 in the town of Lassa, Nigeria, this virus is transmitted either from animals to humans, by contact with food or household products contaminated by the excrement or urine of a Mastomys type rodent – originating from Africa and living near homes – either from person to person, through direct contact with the secretions of an infected person.

The incubation period varies from 2 to 21 days. According to the Pasteur Institute, this fever infects 100,000 to 300,000 people per year and causes 5,000 to 6,000 deaths. Asymptomatic infection occurs in 80% of cases. The remaining 20% ​​may, however, experience first “stark” symptoms, such as vomiting, nausea, abdominal pain, headaches, myalgia, arthralgia, asthenia, etc. These are followed by edema, “hemorrhagic signs”, “pericardial and pleural effusions” and “more rarely” encephalitis.

According to the WHO, the fatality rate of the pathology is 1%, and 15% for patients with severe forms. The patient died in a context of “renal and hepatic failure”, continues the Pasteur Institute. Lassa fever is particularly dangerous for pregnant women, who frequently die along with their fetus.

For infected and symptomatic people who survive, after-effects are possible. Severe fatigue, malaise and dizziness may persist for several weeks. “A third of these patients present serious after-effects: unilateral or bilateral deafness, temporary or permanent, and myocarditis,” continues the institute.

There is currently no vaccine against Lassa fever. Only one molecule is effective if administered early after infection: ribavirin. “However, the clinical signs at the onset of the disease are similar to those observed for other pathologies, such as malaria or dysentery, which are very common (in Africa). The involvement of the Lassa virus is therefore often only considered several days after the appearance of symptoms,” concludes the Pasteur Institute.