United States health officials have confirmed that the virus causes babies to be born with abnormally small heads and severe brain defects, confirming the worst fears of many pregnant women in the US and Latin America. Doctors in Brazil have been linking Zika infections in pregnant women to a rise in newborns with microcephaly – an unusually small skull – since last year.
Most outside experts were cautious about drawing such a connection but the US Centers for Disease Control and Prevention says it has enough evidence to confirm that. “There is no longer any doubt that Zika causes microcephaly,” Tom Frieden, CDC director, said on Wednesday.
The CDC said it is also clear that Zika causes other serious defects, including damaging calcium build-ups in the developing brain. Among evidence that clinched the case was that signs of the Zika virus, which is spread primarily through mosquito bites and can also be transmitted through sex, have been found in the brain tissue, spinal fluid and amniotic fluid of microcephaly babies.
The CDC and other health agencies have been operating for months on the assumption that Zika causes brain defects. They have been warning pregnant women to use mosquito repellent, to cover up, to avoid travel to Zika-stricken regions and either to abstain from sex or to rely on condoms. Those guidelines will not change.