When Zika virus first hit Brazil five years ago, the impact was devastating. Cases of infection with the virus began to be detected in adults in Brazil in early 2015, and then began spreading across the Americas.
But it wasn’t until the second half of 2016 that paediatricians started to see an increase in cases of microcephaly, a condition in which babies are born with a small head and sometimes brain damage, in newborns.
That year, researchers confirmed that infection with Zika during pregnancy can cause lasting brain damage in some fetuses, which can lead to arrested brain development in babies. Some babies didn’t survive. Those that did are now around 4 years old.
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Neurologists are now learning that congenital Zika syndrome – the name of the condition the virus causes in children who were infected as fetuses – can be divided into at least two groups, based on the children’s symptoms. This could help determine which therapies may be potentially helpful for those affected.
“Zika really was a disaster here in Brazil,” says Heloisa Pereira, a paediatric neurologist at Rio de Janeiro State University. “We knew nothing about the disease.”
of Brazilian national health records found that of more than 6.8 million births in the country between 1 January 2015 and 23 May 2017, nearly 2,800 babies were born with microcephaly and structural brain damage. Forty-one in every 10,000 women who were infected with Zika virus in the first trimester, and 17 women in every 10,000 infected in the second trimester, gave birth to a baby with microcephaly.
Read more: Zika virus outbreak: What you need to know
Along with her colleagues, Pereira has been studying a group of 75 children in Campina Grande, ParaĂba, in north-east Brazil.
Brain scans of the children show that their brains have the hallmarks of congenital Zika syndrome. “Most of them were born with microcephaly. Most of them cannot speak and are completely dependent,” says Pereira.
But when Pereira and her colleagues examined the children, they noticed two separate sets of symptoms. The predominant symptoms in 48 of the children included tight muscles, involuntary muscle spasms and atypical reflexes.
In 23 of the children, the predominant symptoms were weak muscles and floppy limbs. Many of these children also had a bell-shaped chest. The remaining four children didn’t quite fit in either group, but there are too few of them to say whether they belong to a third group of congenital Zika syndrome symptoms, says Pereira.
A better understanding of the subcategories of congenital Zika syndrome could improve how it is managed, says Pereira. She recalls one boy who couldn’t speak and appeared to have behavioural issues. But after a thorough evaluation, Pereira’s team found that it was the boy’s distorted posture that was upsetting him.
“When we could posture him properly, and give him some comfort, we could see a completely different child,” she says. “He was very calm and smiling for us all the time… we could see that his cognition might not be as severely affected as it initially seemed.”
Physical and speech therapies are likely to be the best options for children affected by congenital Zika syndrome. That is partly because we don’t have a way of preventing brain damage from occurring. We know that the Zika virus – transmitted by mosquitoes or through sexual contact – can also pass from a mother to her fetus via the placenta, and we know that it appears to target developing neurons and their connections between brain regions.
Remaining questions
People living in poorer areas of Brazil seem to have been more likely to be infected with the Zika virus, and more severely affected, than wealthier citizens, says Pereira. “There seems to be some environmental factor that influences the severity [of an infection],” she says.
There are still plenty of things about Zika virus syndrome that we don’t understand. We don’t know why some babies with the condition develop microcephaly while others have few symptoms, for example. We aren’t sure why infections earlier in pregnancy seem to be associated with worse outcomes. And there have been of women who gave birth to one healthy twin and another with Zika-related brain damage.
And we don’t know what kind of support the affected children will need as they grow. They are likely to need extra educational support when they start school in the next year or so, says Sarah Mulkey, a fetal neonatal neurologist at Children’s National Hospital in Washington DC.
Some effects of the syndrome, such as the impact on a child’s ability to plan and organise, might only become apparent from the age of eight, says Mulkey. “It may go on to affect their employment,” she says. “We need to keep following them long term.”
In the meantime, there is a significant risk that Zika could make a comeback. While there have been no large outbreaks since 2016, the virus in several countries – and there is no vaccine.
Viruses like Zika “have a pattern of coming back at some point again – sometimes they come back every five or 10 years”, says Mulkey. “We definitely need to be concerned that this could happen again.”
The Lancet Child & Adolescent Health
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