Is Zika virus causing a spike in microcephaly in babies?
New evidence is pointing to a strong link between Zika virus and microcephaly in babies while other research suggests the rare condition was in Brazil years before the mosquito-borne virus surfaced.
On Wednesday, the Centers for Disease Control and Prevention in Atlanta said Zika virus was found in tissue samples from two babies with microcephaly who died within 20 hours of birth along with two miscarried fetuses.
All four mothers had signs of Zika virus during the first trimester of pregnancy.
In another case, also released Wednesday in the New England Journal of Medicine, academics document an incident involving a European woman who had spent time in Brazil. In February 2015, she became pregnant there and fell ill 13 weeks later, with what was suspected to be Zika virus.
She returned to Europe at 28 weeks pregnant and terminated her pregnancy four weeks later. Testing pointed to fetal anomalies. The fetus showed “prominent microcephaly.”
For months, global health officials have suspected a link between Zika virus and microcephaly as Brazil grapples with the biggest epidemic of the virus to date.
Health officials in El Salvador, Brazil, Jamaica, Ecuador, Honduras and Colombia told residents to stave off pregnancy until doctors better understand if the infection tampers with brain development in infants. So far, it’s been linked to a 20-fold increase in microcephaly in babies, in which the newborns are born with irregularly small heads and underdeveloped brains.
But a study published last week by the World Health Organization suggested that there was a rise in babies born with abnormally small heads since 2012 – three years before Zika virus surfaced in Brazil.
In this study, Brazilian scientists looked at the health data of 16,208 babies born in Paraiba region since 2012. Up to eight per cent matched the criteria for microcephaly – that’s 648 babies born with the rare condition since 2012.
“Some people are saying perhaps this is not new, perhaps it’s been here all along. It’s what we call a reporting bias, where when we look for something, you find it,” Dr. Isaac Bogoch, a tropical infectious disease specialist at Toronto General Hospital and the University of Toronto, told Global News.
Scientists need to consider if these cases are being detected because of increased surveillance. But the case reports on finding Zika in the brain tissue of developing babies with microcephaly are striking, he said.
“It’s a significant finding and it raises more questions. It’s another arrow pointing in the right direction. They’re clues but by no means can we say that one thing causes another,” he explained.
Jason Tetro, a Canadian microbiologist and author of The Germ Files, says there are many factors at play. It isn’t as simple as saying Zika virus definitely causes microcephaly, for example.
“The problem with Zika virus is it can go throughout the body. We’ve seen it in saliva, in urine, in semen, but you would have to somehow break the maternal fetal barrier in order to cause infection in the baby,” he explained.
“Most likely this is due to some kind of compromised immune system in the mother. It could very well be that the mothers have a weakened immune system due to environmental factors,” he said.
READ MORE: Should Canadians worry about Zika virus?
Experts hypothesize that Zika in the blood of a pregnant woman crosses into the placenta and affects the fetus during a critical time in neurological development and growth in the central nervous system.
Both Canadian experts cautioned that more research needs to be done about the virus the medical community is steadfastly working to unravel.
“We still need to understand the mechanism of infection in the brain before we can jump to any conclusions either supporting or detracting from Zika virus as the cause of microcephaly,” he said.
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