Autochthonous chikungunya and dengue fever outbreak in Mainland France, 2010-2018

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.

[Entomological factors of arboviruses emergences]

Arboviruses - viruses transmitted by haematophagous arthropods - are responsible for febrile syndromes, which sometimes include haemorrhagic or neurological symptoms. Human activities have facilitated the emergence of these originally zoonotic viruses and the domestication and spread throughout the world of their major vectors. The last decade has seen significant changes in the epidemiology of arboviruses transmitted by mosquitoes of the genus Aedes, particularly in relation to the intercontinental spread of Aedes albopictus. Here, we address the epidemiological consequences of the invasion by this species into Central Africa and Europe in a context of viral globalization. The risk of transmission in these areas is influenced by virus-vector adaptation phenomena as well as environmental phenomena including climate. Faced with these new risks, it is essential to develop competences in entomological and virological surveillance, risk assessment and forecasting of epidemic risk in order to develop strategies for the prevention and control of epidemics.

Chikungunya outbreak in Montpellier, France, September to October 2014

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.

The moth Hylesia metabus and French Guiana lepidopterism: centenary of a public health concern

The females of the moths Hylesia metabus have their abdomens covered by urticating hairs looking like micro-arrows and causing a puriginous dermatitis to humans known as “papillonite” in French Guiana and also called yellowtail moth dermatitis or Caripito itch. The densities of the moths show great seasonal and annual variations depending on mechanisms mostly unknown. When H. metabus infestations occur, numerous cases of dermatologic manifestations are reported from people living near the mangrove swamps where the moths are developing. One hundred years after the first “papillonite” epidemic reported from French Guiana in 1912, the data presented herein summarize the actual state of knowledge on H. metabus biology and ecology and on the lepidopterism. Some recommendations are proposed for the surveillance and warning systems of H. metabus infestations and to avoid contact with the moths. Research priorities are suggested to improve the control against this problem emerging between nuisance and public health.

First two autochthonous dengue virus infections in metropolitan France, September 2010

In September 2010, two cases of autochthonous dengue fever were diagnosed in metropolitan France for the first time. The cases occurring in Nice, southeast France, where Aedes albopictus is established, are evidence of dengue virus circulation in this area. This local transmission of dengue calls for further enhanced surveillance, active case finding and vector control measures to reduce the spread of the virus and the risk of an epidemic.

First two autochthonous dengue virus infections in metropolitan France, September 2010

In September 2010, two cases of autochthonous dengue fever were diagnosed in metropolitan France for the first time. The cases occurring in Nice, south-east France, where Aedes albopictus is established, are evidence of dengue virus circulation in this area. This local transmission of dengue calls for further enhanced surveillance, active case finding and vector control measures to reduce the spread of the virus and the risk of an epidemic.