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.
Brazil's Zika epidemic is worse than thought as 80 per cent of those infected have no symptoms, the country's health minister has said.
Marcelo Castro told Reuters news agency that local governments will be ordered to start reporting details of cases next week under stringent new measures in an attempt to combat the outbreak.
Zika has been linked to serious brain defects in unborn babies when their mothers catch the illness.
Test kits to diagnose the virus, which is passed through bites from infested Aedes mosquitoes, will be distributed this month, said Mr Castro.
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.