On May 2, a patient suffering from Lassa feversoldier returning from abroad, was admitted to Bégin hospital in Saint-Mandé (Val-de-Marne), in the Paris region. It’s about first case recorded in France for this fatal and endemic disease in West Africa. Can we cure it? Is there a risk of an epidemic in Europe? Explanation sequence.
Investigation underway to identify contact cases
According to the WHO (World Health Organization), Lassa fever is a hemorrhagic fever, meaning it can lead to death due to bleeding. First identified in Lassa, Nigeria, in 1969 (hence its name), it is now endemic in West Africa where we identify 100,000 to 300,000 infections each year.
This disease is extremely rare in the Northern hemisphere, on average in Europe there is only one case every two years. In France, an investigation was launched to identify contact cases of the sick patient (whose condition is now stabilized) to prevent and monitor them: these will be treated as quickly as possible if symptoms appearto avoid any risk of epidemic.
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Additional difficulty: Lassa fever is very difficult to diagnose because infected individuals have no symptoms until the disease occurs. After infection, it was only one to three weeks later that first symptoms appearin 20% of cases: fever, vomiting, nausea, stomach aches and headaches, fatigue, muscle and joint pain.
5,000 to 6,000 deaths per year, and no vaccine…
Then, in the event of a more severe infection, some patients may suffer from edema, hemorrhages, inflammation of the brain (encephalitis) or blood loss in the heart and rib cage. 5,000 to 6,000 deaths are recorded each year: pregnant women are particularly at risksince they have little chance of survival and the fetus 100% dies.
For patients lucky enough to survive (15% mortality for severe forms), symptoms generally fade after one to four weeks. Transmission of the disease occurs through blood or saliva contact, but not through the air.which fortunately minimizes the risk of an epidemic.
Lassa fever is transmitted by the Natal rat, via its excrement. This animal lives close to humans in West Africa, in the foundations of homes, which facilitates transmission.
For now, no vaccine is available, despite encouraging trials carried out by the Institut Pasteur since 2019. For the moment, it is an antiviral medicine that is used to treat this disease: ribavirina molecule also used to treat hepatitis C.
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The problem is that ribavirin is often administered without knowing if it is really Lassa fever, since the symptoms resemble those of other diseases such as malaria or dysentery. And when it is indeed Lassa fever, the medicine is often given too late : for maximum effectiveness, taking a few days after infection would be necessary.
