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Abstract
Abstract
In July 2018, one autochthonous case of West Nile virus (WNV) infection was identified in Nice, Provence-Alpes-Côte d’Azur (Paca). We investigated to determine the potential place of infection and the extent of viral circulation in the area, in order to guide control and preventive measures. In affected areas, we raised awareness of health professionals on WNV infections, substance of human origin safety relied on nucleic acid testing for WNV and on deferral of blood donors indicating minimum one night of stay in the areas for 28 days. Equine, wild bird and entomologic surveillance activities were reinforced. The human arboviruses national reference laboratory (NRL) retrospectively tested samples from hospitalized individuals from June 1st with meningitis and encephalitis around Nice. We tested negative suspected autochthonous cases of chikungunya and dengue infections notified since July in Paca and presenting WNV compatible symptoms. Measures were adapted along identification of additional cases.
We identified 27 autochthonous cases, with onset of symptoms between July 7th and November 12th: 24 in Paca, 2 in Corsica and 1 in Occitanie. Seven cases presented neuroinvasives symptoms, 18 flu-like symptoms and 2 were asymptomatic. One blood donation and 2 organs tested positive for WNV. The animal NRL identified 13 equine cases (1 in Paca, 5 in Corsica and 7 in Occitanie) and 4 infected raptors with nervous symptoms (3 in Paca and 1 in Corsica). Genomic characterization of the virus identified a strain belonging to the lineage 2 among 2 raptors. No virus was found in mosquitoes captured in affected areas.
Since 2000, six episodes of WNV transmission were reported in France but none with this extent. For the first time, the lineage 2, circulating in Italy and other European countries, was isolated in France which might be changing epidemiological situation. Therefore, surveillance activities should be revised in order to promptly secure blood products.
Key messages
We describe the most important episode of West Nile Virus transmission identified in humans in France. In 2018, West Nile virus lineage 2 was isolated for the first time in France which might change the epidemiological situation in the country.
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Abstract
Abstract
Background
Aedes albopictus, vector of dengue and chikungunya viruses, is implanted in mainland France, exposing to the risk of autochthonous transmission. Since 2006, epidemiological and entomological surveillance activities aim to prevent or limit the occurrence of autochthonous cases. We aimed to describe episodes of transmission and control measures implemented in order to reflect on surveillance activities.
Methods
We reviewed all publications and documents produced on autochthonous transmission episodes in France and surveillance protocols. We reviewed surveillance activities, investigation methods and control measures implemented.
Results
Between 2010 and 2018, eight episodes of autochthonous dengue fever transmission and three of chikungunya were recorded in mainland France. All of them occurred in the South east of France, between July and October, when vector density was the highest. Transmission areas were limited to single domestic houses located in discontinuous urban areas. Only two episodes happened in two distinct areas. Chikungunya episodes led to 31 cases and dengue fever episodes to 23 cases. Most cases were identified by door-to-door investigations set-up in transmission areas. We isolated serotypes 1 and 2 for dengue and East Central South Africa lineage for chikungunya in autochthonous cases. Adulticide vector control measures were effective in controlling transmission.
Seven episodes of transmission were due to failure in identifying primary imported cases. Four episodes occurred because of the absence or the lack of vector controls measures around primary imported cases.
Conclusions
Surveillance activities, and autochthonous cases investigations, were effective in limiting the extent of transmission, but were highly demanding for surveillance actors. Identified causes of transmission highlight the need of regular awareness campaigns targeting physicians and biologists.
Key messages
Effectiveness of the surveillance system of dengue, chikungunya and zika viruses, and autochthonous cases investigations. Needs of awareness and training courses targeting health professionals to the risk represented by these viruses.
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Abstract
In October 2014, an outbreak of 12 autochthonous chikungunya cases, 11 confirmed and 1 probable, was detected in a district of Montpellier, a town in the south of France colonised by the vector Aedes albopictus since 2010. A case returning from Cameroon living in the affected district was identified as the primary case. The epidemiological investigations and the repeated vector control treatments performed in the area and around places frequented by cases helped to contain the outbreak. In 2014, the chikungunya and dengue surveillance system in mainland France was challenged by numerous imported cases due to the chikungunya epidemic ongoing in the Caribbean Islands. This first significant outbreak of chikungunya in Europe since the 2007 Italian epidemic, however, was due to an East Central South African (ECSA) strain, imported by a traveller returning from West Africa. Important lessons were learned from this episode, which reminds us that the threat of a chikungunya epidemic in southern Europe is real.
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