ECDC Rapid Risk Assessment: Zika virus disease in Var department, France

On 1 October 2019, a case of locally acquired Zika virus (ZIKV) disease in France (Hyères city, Var department) was laboratory confirmed. The case had symptoms compatible with ZIKV disease during the first half of August 2019. The case did not report any history of travel to countries with historical ZIKV transmission. No evidence of sexual transmission was retrieved during the investigation. No imported ZIKV disease cases were reported in the area in 2019. Further epidemiological investigations are ongoing to define the most probable mode of transmission. At this stage, vector-borne ZIKV transmission is the hypothesis that forms the basis for this ECDC risk assessment. If this hypothesis turned out to be correct, this event would mark the first case of autochtonous vectorborne transmission of ZIKV in Europe. Vector control measures are being implemented near the residence of the case. To date, investigations have not managed to identify additional cases, but further cases may be detected through ongoing active case finding.

Ae. albopictus is widely established in southern Europe (see Ae. albopictus, current known distribution, August 2019) and a competent vector for ZIKV. However, it is considered a less competent vector than the tropical and subtropical vector Ae. aegypti. The occurrence of sporadic cases or clusters of locally acquired vector-borne ZIKV cases is possible, notably in the Mediterranean region of Europe when environmental conditions during summer and early autumn can support vector abundance and arbovirus replication at a level that is sufficient for autochthonous transmission of ZIKV. The report of a locally acquired ZIKV disease case in the southern part of France is thus not unexpected.

To date, and based on ECDC's epidemiological assessment, the probability of ongoing vector-borne local transmission in Hyères (and surrounding areas) is considered very low because current evidence does not indicate the existence of a more extensive cluster of ZIKV cases. As temperatures are progressively decreasing during autumn, the environmental conditions are currently not favourable for sustained transmission. The current risk posed to the population, including pregnant women and their unborn children, is very low. If autochthonous, vector-borne cases could be documented, for example by detecting additional locally acquired cases in the immediate vicinity of the case, the risk for pregnant women and unborn children would be low instead of very low. It is possible that the ongoing investigation will retrospectively identify locally acquired cases because Ae. albopictus abundance at the time the case had symptoms would have allowed vector-borne transmission. Currently, however, there is a very low likelihood that travellers to this area will become infected, introduce the virus, and initiate further local transmission in their EU/EEA country of residence. Substantial uncertainty regarding possible local transmission at the time of publication remains. The level of risk should be re-assessed when significant new facts become available.

In the case of confirmed vector-borne transmission, Member States may consider applying risk control measures that are outlined in the previous ECDC Rapid Risk Assessment Zika virus transmission worldwide.