Brazil says the number of babies born with suspected microcephaly or abnormally small heads since October has now reached nearly 4,000.
In the worst affected area, about 1% of newborns have suspected microcephaly.
The Brazilian authorities believe the increase is caused by an outbreak of Zika virus. Just 150 babies were born with microcephaly in 2014.
The brain condition can be deadly or cause intellectual disability and developmental delays.
Colombia's health minister has advised women there to delay pregnancy.
This thread title has been edited on request of the OP as this discussion no longer about just Brazil. kiore