'My daughter is in constant pain': desperate mother tells of raising a baby affected by the Zika virus
The mother of one child has told ITV News that her daughter appears to be in constant pain.
Another said that there had been no warnings and her pregnancy had been trouble-free.
Believed to cause brain defects in babies, the virus is "spreading explosively" according to the World Health Organisation.
John Ray reports from Recife, a city in northeastern Brazil that is taking the brunt of the epidemic:
The mosquito-borne infection is currently centred on Latin American countries, with Brazil suffering an estimated 1.5 million cases.
Experts believe it may affect up to four million people this year.
Scientists are searching for a vaccine and believe they may have two possible candidates but they may not be available for several years and at the moment there is nothing to stop the virus.
The army in Brazil has been mobilised with orders to eradicate the mosquito that lives in rubbish-filled stagnant waters.
However, officials are fighting a losing battle against the prolific species.
In Recife the local head of police has only a 10-strong team to a population of 150,000.