On 28 August, French authorities reported 5 cases of chikungunya fever on Réunion Island: three confirmed, one probable and one suspected under investigation. All three confirmed patients presented with an acute febrile syndrome, arthralgia, myalgia and cutaneaous rash. All live in the same area of Saint-Gilles-Les-Bains, on the western side of the island. The probable and suspected case both have stayed in the same or in a neighbouring area before the onset of their symptoms.
None of the three confirmed cases had a history of recent travel. They represent the first autochthonous chikungunya cases on the island since the large outbreak in 2005-2006, when 38% of the island’s population was infected.
In spite of the current low activity of Aedes albopictus, the only vector for chikungunya virus on the island, the autochthonous cases show that the virus is circulating on Réunion Island. Therefore, such virus circulation may increase in the coming southern summer months with increasing vector activity.
Réunion Island being a popular touristic destination, the possibility of imported cases on continental Europe should be considered, where the Aedes albopictus vector is widely present, mainly in Southern Europe. However, the opposite seasonality of the southern versus the northern hemisphere limits the risk for the establishment of widespread virus transmission cycles on the continent, where mosquito activity is starting to decrease. Moreover, this risk is considered much lower than the risk from importation related to the previously reported outbreaks in South-East Asia, from where thousands of cases have been reported during the northern hemisphere summer.
Awareness among clinicians and public health authorities for chikungunya fever is to be strengthened for the whole duration of the vector activity season, as is being done in most European areas where the vector is known to be present.