“No health system in the world could cope with a full blown outbreak of the virus,” said Dr Scally.

An Irish tropical diseases expert has warned there are “lots of unknowns” about the Zika virus epidemic.

Malaria vaccines developed by Irish and British scientists have been shown to produce a strong immune response in a human trial.

Travellers were urged today to get vaccinated before going abroad after one in four people revealed they fell ill on holiday.