Countries including South Africa and Trinidad and Tobago have confirmed their first cases of Zika virus.
More than 5,000 pregnant women in Colombia have contracted the virus, its government has said.
A fourth British traveller has been diagnosed with the Zika virus since the beginning of the current outbreak, Public Health England has said.
The person had recently returned from Venezuela.
It brings the total number of cases detected in the UK in 2016 up to four.
Only two cases were diagnosed in Britain through the whole of last year, in travellers who had visited Colombia and Guyana or Suriname.
Britain's camp for the Rio Olympics should be moved to a Zika-free location outside Brazil, Jessica Ennis-Hill's coach has said.
The mother of Zika "bucket baby" Jose Ferreira is holding out hope despite doctors' fears over his future.
The government has told airlines to take the measure on all flights travelling to the UK from countries with confirmed transmission of Zika.