France - Confirmation of the circulation of West Nile virus in the region of Nice - 2 human cases

[Gert van der Hoek]

January 11, 2018

Following the identification of two patients in the department of Alpes-Maritimes (Nice and Vence) who developed a flu-like form of West Nile virus infection in August / September 2017 (Box), an investigation initiated by DGAl was piloted by DDecPP Alpes-Maritimes to identify possible equine cases and estimate the circulation intensity of West Nile virus in this species. The survey concerned 151 equines of the equestrian center of Nice (located about 5 km from the human case confirmed in Nice), either horses belonging to the equestrian club, or horses owners staying at the equestrian center, as well as some horses from the Municipal police patrol in the center of Nice. The departmental laboratories of Bouches-du-Rh?ne and H?rault, as well as the animal health laboratory of ANSES Maisons-Alfort (for confirmation), carried out the analyzes consisting of ELISAs for West Nile IgM capture. identification of IgM confirming recent infection with West Nile virus in the equidae collected.

In total, only one equine had West Nile IgM; this is the only confirmed case of West Nile virus infection in equines from the Alpes-Maritimes, this infection having gone unnoticed in this animal. This result confirms that there was a West Nile virus circulation in Nice this year, but with a seroprevalence of 0.7% in the equidae tested (against 16.9% following the epizootic in the Camargue in 2015, estimated at the IFCE OPium survey), the circulation appears to be of low intensity.

A septuagenarian living in Nice, presented on September 4, 2017 symptoms suggestive of arbovirosis (rash, myalgia, arthralgia, headache = not typical signs for West Nile). The diagnosis of confirmation of West Nile virus infection was made on October 20th. Epidemiological evidence for this patient supports aboriginal contamination (mosquito bite). No clinical case of West Nile virus infection has been reported in horses or birds in this area. Enhanced animal surveillance measures have been taken, cf. infra.

Following this first human case, a search was conducted in the arbovirosis surveillance database of patients residing in the Alpes-Maritimes and for whom the Chikungunya-Dengue-Zika results were negative. A new confirmed case of WNV (IgM positive and neutralizing antibodies specifically WNV) was identified on October 26th. The 48-year-old resides in Vence (06). However, between August 7th and 21st she stayed in the Alpes-Maritimes (Vence, Andon, Saint Martin de Vesubie, Pont du Loup), in the Var at Fr?jus (but only on August 5th) and in Bouches-du-Nord. -Rhone (Cuges les Pins). She says she has never been to Nice.

Seasonal human surveillance for West Nile virus infections, normally from June to October, has been extended to November 15, 2017.

https://www.plateforme-esa.fr/artic...ion-du-virus-west-nile-dans-la-region-de-nice