A new study has allowed scientists to watch the Zika virus destroy nascent brain cells in mice fetuses, proving definitively the link between the virus and birth defects in humans as well as cementing suspicions that the strain of Zika spreading in Latin America is a more dangerous mutation than those seen previously.
Three teams of scientists independently conducted different studies on mice fetuses, Reuters notes, all finding similar damage to unborn mice whose mothers are injected with Zika. The scientists watched under microscopes as the virus spread into the fetuses’ brains and began to destroy them before the unborn mouse could properly develop. Signs of microcephaly in cases where the virus was introduced later in development were common; in those in which Zika was introduced in the earlier stages of a pregnancy, the fetus died before being born.
Results of one of these studies, published in the journal Nature, also compared the damage caused by the long-known strain of Zika originating in Africa to that caused by the virus currently spreading in Latin America and native to the South Pacific. The African strain — which, due to its presence being known for decades, is more commonly available in sample form for scientists to conduct experiments with — caused significantly less damage in the unborn mice than the Latin American strain.
“Our findings support the hypothesis that microcephaly is a distinctive feature of recent Zika virus Asian-lineage virus, which originated in the Pacific and is now spreading in South and Central America,” the Brazilian researcher Patricia Beltrão-Braga wrote in her study. Such a mutation in the virus would help explain why the reaction towards the virus in Brazil, Colombia, and other affected areas was initially so muted: The Zika doctors knew it was not as great a threat.