杏吧原创

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鈥檛 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鈥檛 survive. Those that did are now around 4 years old.

Neurologists are now learning that congenital Zika syndrome 鈥� the name of the condition the virus causes in children who were infected as fetuses 鈥� can be divided into at least two groups, based on the children鈥檚 symptoms. This could help determine which therapies may be potentially helpful for those affected.

鈥淶ika really was a disaster here in Brazil,鈥� says Heloisa Pereira, a paediatric neurologist at Rio de Janeiro State University. 鈥淲e knew nothing about the disease.鈥�

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.

Along with her colleagues, Pereira has been studying a group of 75 children in Campina Grande, Para铆ba, in north-east Brazil.

Brain scans of the children show that their brains have the hallmarks of congenital Zika syndrome. 鈥淢ost of them were born with microcephaly. Most of them cannot speak and are completely dependent,鈥� 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鈥檛 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鈥檛 speak and appeared to have behavioural issues. But after a thorough evaluation, Pereira鈥檚 team found that it was the boy鈥檚 distorted posture that was upsetting him.

鈥淲hen we could posture him properly, and give him some comfort, we could see a completely different child,鈥� she says. 鈥淗e was very calm and smiling for us all the time鈥� we could see that his cognition might not be as severely affected as it initially seemed.鈥�

Physical and speech therapies are likely to be the best options for children affected by congenital Zika syndrome. That is partly because we don鈥檛 have a way of preventing brain damage from occurring. We know that the Zika virus 鈥� transmitted by mosquitoes or through sexual contact 鈥� 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. 鈥淭here seems to be some environmental factor that influences the severity [of an infection],鈥� she says.

There are still plenty of things about Zika virus syndrome that we don鈥檛 understand. We don鈥檛 know why some babies with the condition develop microcephaly while others have few symptoms, for example. We aren鈥檛 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鈥檛 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鈥檚 National Hospital in Washington DC.

Some effects of the syndrome, such as the impact on a child鈥檚 ability to plan and organise, might only become apparent from the age of eight, says Mulkey. 鈥淚t may go on to affect their employment,鈥� she says. 鈥淲e need to keep following them long term.鈥�

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 鈥� and there is no vaccine.

Viruses like Zika 鈥渉ave a pattern of coming back at some point again 鈥� sometimes they come back every five or 10 years鈥�, says Mulkey. 鈥淲e definitely need to be concerned that this could happen again.鈥�

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