Spain has recorded its first known case of the Zika virus being sexually transmitted, after a woman contracted it from her partner after he returned from a Latin American country, health authorities in Madrid said on Friday.

The mosquito-borne Zika virus has been linked to thousands of cases of the microcephaly birth defect in countries such as Brazil, which has declared a public health emergency over the disease. The birth defect is marked by babies born with brain abnormalities and undersized heads.

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The woman's partner had been diagnosed with Zika shortly after returning from an unspecified country in Latin America in either late April or early May, a spokesman for Madrid's health authorities said.

The woman, who is from Madrid, probably contracted it just after he returned, the spokesman said. Spanish media reported that the woman is not pregnant.

Before the announcement of the new case, Spain had 158 known cases of Zika infections at last count, all of which resulted from traveling overseas.

(Reporting by Angus Berwick, editing by Larry King)