West Nile virus still circulating in Var, 11 cases identified in France in 2024

Since the beginning of the year, 10 cases have been detected in the Var and one in Guadeloupe, on August 7.

Five new indigenous human cases of West Nile virus infection have been recorded in the Var, franceinfo learned from the Var regional health agency (ARS) on Thursday, August 29. In total, France has had 11 indigenous cases since the start of 2024: one case in Guadeloupe in early August and 10 cases in the Var since mid-July. “Among these 10 cases, four presented neuro-invasive forms requiring hospitalization”indicates the ARS.

More than a month after the first cases, on July 15, the West Nile virus is still circulating in the Var department, the only one in mainland France that has so far recorded indigenous human cases, i.e. caused by an infected mosquito and circulating in mainland France. In addition to Ollioules, La-Seyne-sur-Mer and Six-Fours-les-Plages, the virus has also been recorded in Sanary-sur-Mer.

Apart from human contamination, health authorities have reported two indigenous equine cases in mainland France. The first was identified in the Var, “in an area delimited by the municipalities of Ollioules, Six-Fours-les-Plages and La-Seyne-sur-Mer”, Public Health France indicates in its summary of August 21. The second case is a horse located in Marseille. In Guadeloupe, the West Nile virus has caused the death of at least three horses among the fifteen cases recorded recently, indicated Guadeloupe The 1st Monday.

The virus is being actively monitored in the overseas departments with a first human case identified on Wednesday August 7 in Guadeloupe. “The West Nile virus is considered today to be the second most widespread flavivirus after dengue fever.”recalled the regional health agency of Guadeloupe. No epidemic has been recorded in Reunion or Mayotte, “but the virus circulates endemically in Madagascar”, adds Public Health France, with an isolated case also identified in Mayotte in 2021.

The virus is transmitted by mosquitoes of the genus Culex, the common mosquito in France which feeds mainly in the evening and at night, to be differentiated from the tiger mosquito (Aedes albopictus). “Culex mosquitoes are infected exclusively through contact with infected birds”specifies the regional health agency of Paca. “Humans and horses are ‘accidental hosts’ of the virus. There is no transmission of the virus from human to human (or from horse to human) via mosquitoes.”

According to data known to health authorities in August 2024, 80% of West Nile virus infections are asymptomatic. In 20% of cases, the patient presents with a “flu-like syndrome (fever, aches, headaches)”. And in less than 1% of infections, there may be neurological complications, especially in immunocompromised individuals.

According to Public Health France, the virus was first detected in 1962 in mainland France and Corsica with human and equine cases in the Camargue. It reappeared in the early 2000s, in the Camargue, Var and Pyrénées-Orientales (five equine cases in 2005). In 2023, human cases were identified for the first time in Nouvelle-Aquitaine (Gironde, Charente-Maritime and Charente), after equine cases were recorded in Gironde in 2022. In total, in 2022, six human cases were recorded in mainland France and Corsica: four cases in Var and two in Haute-Corse.

In 2023, in mainland France and Corsica, 43 human cases of indigenous infection were identified in three regions: 33 cases in Nouvelle-Aquitaine (26 cases in Gironde, five in Charente-Maritime, two in Charente); two cases in Corsica; eight in Paca (three in Alpes-Maritimes, three in Bouches-du-Rhône and two in Var).