RIO DE JANEIRO (Reuters) - Brazil's government, grappling with the outbreak of the Zika virus, on Wednesday said it had lowered the head circumference used to measure suspected cases of microcephaly, a move meant to align its norms with those of the World Health Organization.
The country's Health Ministry, updating a weekly tally for cases of microcephaly linked to the Zika outbreak, said that baby boys suspected of having the condition at birth must have a head circumference equivalent to or less than 31.9 cm (12.56 inches). For female infants, the cutoff is now 31.5 cm.
Brazil had previously been working with a 32-cm cranial circumference for both sexes to diagnose microcephaly, a birth defect marked by abnormally small heads and that can lead to developmental problems.
Though the link between the virus and microcephaly has not been scientifically established, traces of the virus have been found in laboratory tests of bodily fluids and tissue of mothers and babies affected by the condition.
The changes, the second revision made by Brazil to its parameters since the outbreak began last year, are an effort to bring the country's guidelines into agreement with new figures recently announced by the WHO.
WHO has been working with Brazil and other affected countries to better understand the condition and determine what links it has with the virus.
Suspected cases of microcephaly counted before the change, but with measurements beyond the new limits, will continue to be investigated until they are either confirmed or ruled out, the ministry added.
"This will help prevent normal children from entering the statistics," Wanderson Oliveira, the ministry's coordinator for emergency response, told reporters in Brasília, the capital.
The ministry on Wednesday said the number of confirmed and suspected cases of microcephaly in Brazil associated with the Zika virus has risen to 4,976 from 4,863 a week ago.
Of these, the number of confirmed cases climbed to 745 from 641 a week earlier, while the number of suspected cases under investigation increased to 4,231 from 4,222 in the same period. So far, 1,182 suspected cases have been ruled out.
Brazil considers most of the cases of babies born with abnormally small heads to be related to Zika.
Reporting by Paulo Prada; editing by Chris Reese, G Crosse