Experts are still searching for confirmation that the Zika virus is the cause of microcephaly – but the odds of an infected mother’s baby having microcephaly remain slim.
“With two recent papers in the past week, we have seen some stronger evidence that Zika virus, but not other viruses that were sought and not found, seems to have a strong affinity for brain tissue but not other tissues. But these reports do not point to a “smoking gun,” says Adjunct Associate Professor Ian Mackay, Professor of Virology at the Australian Infectious Diseases Research Centre at the University of Queensland.
“The presence of Zika virus genetic material in the brain tissue of a fetus during a time of an epidemic of that virus is not proof that the virus causes the brain injuries,” he says.
“Proving that link will take some time and will be hard to achieve.”
He says the odds are “very slim” that an infected pregnant woman’s baby would be affected by microcephaly.
“If Brazil’s numbers hold up – and that is still under investigation – roughly 4,000 diagnoses of microcephaly occurred from among 3 million births in 2015,” he says.
A Victorian woman has been diagnosed with Zika virus following an earlier case in Queensland.
Professor Cheryl Jones, Professor of Paediatrics at The University of Sydney and Marie Bashir Institute for Infectious Diseases and Biosecurity, and President of the Australasian Society for Infectious Diseases, says it is not yet known if Zika causes microcephaly.
“A causal link is biologically plausible as mother to child transmission of Zika virus during pregnancy can occur, and Zika virus has been detected in pathological tissues including the brain of fetal losses.
“An increase in babies born with microcephaly in Brazil occurred at the same time as increases in Zika virus infection in the population.”
Meanwhile, a group of physicians in Argentina say that a pesticide called pyriproxyfen may be the cause of the increase in cases of microcephaly.