Characterization of the first autochthonous dengue outbreak in Spain (August-September 2018)

On October 3rd 2018, dengue virus (DENV) infection was confirmed in three family members (symptoms onset between August 18th and 27th) without travel history outside of Spain. They had been together in the Autonomous Communities (AC) of Murcia and Andalusia. By the end of October, a second cluster of two dengue cases (symptoms onset on September 27th and 30th) was confirmed in the AC of Murcia. DENV type 1 sequence was identical to the first cluster, and the epidemiological link was a visit from a case of the first cluster to a fruit-farm neighboring the small village of residence of the second cluster. The entomological investigation found Aedes albopictus activity in this area although all mosquitoes were PCR-negative for DENV. This is the first autochthonous dengue outbreak identified in Spain. This outbreak highlights challenges to timely detect and respond to DENV transmission and opens questions on dengue dynamics in a non-endemic context.