Roughly 4000 babies have been born with microcephaly in Brazil since October Mario Tama/Getty

Microcephaly – babies born with brain damage and abnormally small heads – has jumped 20-fold in Brazil since the Zika virus arrived there. We don’t yet know how this condition will affect the lives of these babies, but early case studies suggest they could have serious brain damage.

Microcephaly is a poorly understood congenital condition in which babies are born with an unusually small head. It is associated with a range of causes, including having a malnourished mother or a genetic condition like Down’s syndrome. Some children born with the condition aren’t neurologically impaired, while others can have severe brain damage.


Since October, roughly 4000 babies with microcephaly have been born in Brazil, and it is strongly suspected that Zika infections during pregnancy are to blame. But what isn’t yet known is how it will affect the children’s development.

“They may not be able to recognise their parents or perceive pain, and will need constant attention because they wouldn’t be able to indicate when they need food or drink,” says Geoff Woods, a clinical geneticist at the University of Cambridge, who has seen brain scans and early case reports from Brazil.

Limited life expectancy

Based on the scans, it appears that the brain stem and the cerebellum are the regions most affected. These oversee many functions that don’t require active thought, such as swallowing, controlling body temperature and blood pressure, says Woods. Impairment of these regions means that the babies are prone to choking and fits. “We expect it to be a disease with a very limited life expectancy,” he says.

The babies are also likely to be intellectually impaired, says Yanick Crow of the Imagine Institute in Paris, France, who has examined three brain scans sent from Brazil. Crow says these Zika-linked cases are similar to Aicardi-Goutieres syndrome, a rare condition caused by an immune over-reaction to viral DNA in the brain.

“The majority of children with Aicardi-Goutieres syndrome have no useful hand, locomotion or verbal function and are severely intellectually affected, and I would fear the same here,” he says.

But it isn’t yet certain that Zika is to blame for Brazil’s rise in microcephaly. “A causal relationship between Zika virus infection and birth malformations has not been established, but is strongly suspected,” Margaret Chan, director-general of the World Health Organization, said last week. “The possible links, only recently suspected, have rapidly changed the risk profile of Zika, from mild threat to one of alarming proportions.”

Supporting the link, Zika has been found in the tissues of five affected babies, and unpublished research suggests the virus may attack the developing forebrain.