The recent, rapid spread of Zika virus in South America and increasing reports of cases of congenital abnormalities spatiotemporally associated with Zika virus infections led WHO to declare a Public Health Emergency of International Concern on Feb 1. WHO also recently described measures that pregnant women should take to avoid infection.

This infection was a neglected tropical disease before 2015 and its natural history is still understudied. Male to female sexual transmission seems possible1 and infectious virus was detected in semen from a patient with haematospermia during the 2013–14 French Polynesia outbreak. 2 We describe the case of a 32-year-old man whose Zika virus infection was identified in January in the Toulouse University Hospital (Toulouse, France). He presented with clinical symptoms typical of an arbovirus infection 2 days after returning to France from Brazil and French Guyana. Molecular tools (RealStar Zika Virus RT-PCR Kit 1.0; Altona Diagnostics GmbH, Hamburg, Germany) were used to rapidly diagnose Zika virus infection, while finding no evidence of either chikungunya or dengue using an inhouse RT-PCR system. He completely recovered in a few days and further blood, urine, and semen samples were collected 2 weeks after diagnosis. Zika virus RNA loads were quantified with a commercial synthetic RNA transcript (Altona diagnostics GmbH, Hamburg, Germany). The RNA virus loads were 2· 8 log10 copies per mL in plasma, 3· 1 in urine, and 8· 6 in semen. The viral load in the semen was roughly 100 000 times that of his blood or urine more than 2 weeks after symptom onset. The reason for this difference is unknown and needs