Pregnant women - or those planning to become pregnant - are being asked to take extra precautions and consider avoiding any travel to countries affected by the Zika virus.

Relatively little is known about the disease, as it was fairly rare until 2013.

Kerly Ariza, 17 and 20-weeks-pregnant, right, stands at her home in Colombia

 This outbreak has now spread to more than 20 countries in South and Central America, after first emerging in Brazil where it has been linked to an increase in incidence of a birth defect affecting babies' brain development.

Professor of Biochemistry at Trinity College in Dublin, Luke O'Neill:

There is no vaccine or treatment and Zika's symptoms are generally mild, with four out of five people unaware that they have caught it.

But Director general of the WHO, Margaret Chan, says it is worrying considering the risk to unborn babies:

Here, the Department of Foreign Affairs and Health Protection Surveillance Centre have issued guidance to Irish people travelling abroad.

They are in line with European advice, which is that pregnant women or those planning a pregnancy should consider postponing any trips to affected areas.

Meanwhile a Danish man who tested positive for Zika after a trip to Mexico and Brazil is expected to recover, and doctors say there is no risk of the disease spreading.