Gert van der Hoek
In Memoriam - Editor, Senior Moderator
On 9 August 2017, Eurofins Biomnis laboratory in Lyon, notified to the French Regional Health Authority a chikungunya virus (CHIKV)-positive test result by real-time reverse transcription PCR (RT-PCR) in a man who had not travelled abroad in the 15 days before onset of symptoms. The National Reference Laboratory (NRL) for arboviruses confirmed the case on 11 August.
This index case lived in a self-contained house in a residential area in Le Cannet-des-Maures. He reported having developed high fever on 2 August, along with strong and incapacitating joint pains in the wrists and fingers, and oedema of extremities. Le Cannet-des-Maures has 4,500 inhabitants and is located in the department of Var in the south-east of France (Figure 1).
The national and regional health authorities initiated a multidisciplinary investigation to determine the source of infection and the extent of CHIKV dissemination.
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[FONT=Conv_MinionPro-Regular]Discussion[/FONT]
Since 2010, three emergences of chikungunya and six of dengue fever occurred in metropolitan France [4-9]. This outbreak with so far nine autochthonous chikungunya cases is the third occurrence of local transmission of CHIKV in France after that in Fr?jus in 2010 and in Montpellier in 2014 [8,9]. The involvement of a CHIKV strain harbouring a mutation facilitating transmission by Ae. albopictus may explain the relative greater number of autochthonous cases observed in 2014 and 2017, compared with 2010.
Chikungunya is an arbovirus transmitted by Aedes mosquitoes, the main vector being Ae. aegypti. The 2006 epidemic of chikungunya in the South West Indian Ocean islands and subsequently in India and South-East Asia revealed that Ae. albopictus can act as an efficient vector of CHIKV [10,11]. This led to the implementation of enhanced arboviral surveillance during the time of vector activity from May to November, in the French departments where Ae. albopictushas been established. This surveillance relies on the mandatory notification of dengue, chikungunya and Zika virus disease cases, and on case finding through a laboratory network. When a case is detected, entomological investigations and, if necessary vector control measures, are implemented in each location visited by the case during their viraemic period [12].
Although up to 75% of chikungunya cases have classical symptoms of chikungunya [13], the primary case was not identified in the present outbreak. Thanks to previous sensitisation of GPs and biologists in the department Var, a region colonised by Ae. albopictus, the outbreak was detected early enough to timely implement vector control measures and to limit its spread. Nonetheless, in order to improve the reactivity of our surveillance system, regular awareness and training campaigns targeting GPs and medical laboratories, focusing on arbovirus diagnosis and reporting, should be conducted. Feedback to all those involved in the resolution of such outbreaks should further increase the acceptability of the system and, as a consequence, improve its efficiency.
Active case finding is still continuing and identified a cluster of two confirmed cases and five suspected cases in a town 10 km from Le Cannet-des-Maures. These cases are currently under investigation and there is an epidemiological link between them and le Cannet-des- Maures.
The present outbreak stresses the importance of long-term vector control in a densely populated residential area where Ae. albopictus is established. In the affected neighbourhood of Le Cannet-des-Maures, man-made mosquito breeding sites, in particular unprotected rainwater storage tanks, were most likely the main drivers of vector densities. Increases in dry periods due to annual climatic variations and possibly climate change on the long term, could lead to wider practice of rainwater storage in the summer. Thus, public awareness campaigns promoting good practices to limit the development of mosquito breeding sites should also focus on the use and appropriate maintenance of mosquito screens to protect water tanks.
LINK TO FULL ARTICLE
This index case lived in a self-contained house in a residential area in Le Cannet-des-Maures. He reported having developed high fever on 2 August, along with strong and incapacitating joint pains in the wrists and fingers, and oedema of extremities. Le Cannet-des-Maures has 4,500 inhabitants and is located in the department of Var in the south-east of France (Figure 1).
The national and regional health authorities initiated a multidisciplinary investigation to determine the source of infection and the extent of CHIKV dissemination.
- snip -
[FONT=Conv_MinionPro-Regular]Discussion[/FONT]
Since 2010, three emergences of chikungunya and six of dengue fever occurred in metropolitan France [4-9]. This outbreak with so far nine autochthonous chikungunya cases is the third occurrence of local transmission of CHIKV in France after that in Fr?jus in 2010 and in Montpellier in 2014 [8,9]. The involvement of a CHIKV strain harbouring a mutation facilitating transmission by Ae. albopictus may explain the relative greater number of autochthonous cases observed in 2014 and 2017, compared with 2010.
Chikungunya is an arbovirus transmitted by Aedes mosquitoes, the main vector being Ae. aegypti. The 2006 epidemic of chikungunya in the South West Indian Ocean islands and subsequently in India and South-East Asia revealed that Ae. albopictus can act as an efficient vector of CHIKV [10,11]. This led to the implementation of enhanced arboviral surveillance during the time of vector activity from May to November, in the French departments where Ae. albopictushas been established. This surveillance relies on the mandatory notification of dengue, chikungunya and Zika virus disease cases, and on case finding through a laboratory network. When a case is detected, entomological investigations and, if necessary vector control measures, are implemented in each location visited by the case during their viraemic period [12].
Although up to 75% of chikungunya cases have classical symptoms of chikungunya [13], the primary case was not identified in the present outbreak. Thanks to previous sensitisation of GPs and biologists in the department Var, a region colonised by Ae. albopictus, the outbreak was detected early enough to timely implement vector control measures and to limit its spread. Nonetheless, in order to improve the reactivity of our surveillance system, regular awareness and training campaigns targeting GPs and medical laboratories, focusing on arbovirus diagnosis and reporting, should be conducted. Feedback to all those involved in the resolution of such outbreaks should further increase the acceptability of the system and, as a consequence, improve its efficiency.
Active case finding is still continuing and identified a cluster of two confirmed cases and five suspected cases in a town 10 km from Le Cannet-des-Maures. These cases are currently under investigation and there is an epidemiological link between them and le Cannet-des- Maures.
The present outbreak stresses the importance of long-term vector control in a densely populated residential area where Ae. albopictus is established. In the affected neighbourhood of Le Cannet-des-Maures, man-made mosquito breeding sites, in particular unprotected rainwater storage tanks, were most likely the main drivers of vector densities. Increases in dry periods due to annual climatic variations and possibly climate change on the long term, could lead to wider practice of rainwater storage in the summer. Thus, public awareness campaigns promoting good practices to limit the development of mosquito breeding sites should also focus on the use and appropriate maintenance of mosquito screens to protect water tanks.
LINK TO FULL ARTICLE