But scientists are alarmed by indications that when it infects a pregnant woman, her baby may be born with a small head and a brain that hasn’t developed properly.
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Two babies died just before they should have been born after their mothers became infected, the global team found. They also found the virus causes a range of birth defects beyond microcephaly.
“The frequency was so high”, said study co-author Karin Nielsen, a pediatric infectious disease specialist at the University of California at Los Angeles, who collaborated with scientists at Fiocruz, an institution in Brazil.
Noting more confirmatory epidemiologic data is still needed from Zika endemic areas, Alyssa Stephenson-Famy, assistant professor at the University of Washington, said: “This is exactly the kind of research that we need to demonstrate a causative link and mechanism between the Zika virus and microcephaly”.
It breeds in tropical areas, including Southeast Asia, which has seen a spike in cases of dengue in recent months and most often causes mild, flu-like symptoms.
Now, laboratory studies have shown that Zika can infect a type of neural stem cell that gives rise to the cerebral cortex of the brain, researchers report in the March 4 issue of the journal Cell Stem Cell. With those, 72 women tested positive for Zika in their blood, urine or both, and 42 of them chose to have ultrasounds.
The study from Brazil, reported Friday in the New England Journal of Medicine, took a closer look during pregnancy.
There is no vaccine to prevent Zika virus infection. The virus has been linked to thousands of suspected cases of microcephaly, a rare birth defect, in Brazil.
New research on the Zika virus is raising concerns. A few cases of Zika have been identified in the US, mostly from travel or sexual transmission. An infected pregnant woman can pass Zika virus to her fetus during pregnancy.
A similar effect in a developing brain could have devastating results.
The other two types of cells were stem cells and neurons.
Dr. Guo-li Ming of Johns Hopkins University, another lead study author, said researchers can now explore questions like how Zika infects the cells.
The White House is inviting officials involved in mosquito control and public health to discuss how best to track and control the spread of the virus and respond when people are infected. Nielsen’s team was able to follow them in real time to see what happened to their pregnancies.
“We’re trying to fill the knowledge gap between infection and the neurological defects”, Dr. Hengli Tang said.
As expected, the Zika virus attacked human progenitor neuronal cells and after three days, 90% were infected and almost a third were destroyed.
According to the World Health Organization (WHO), the Zika virus outbreak is likely to spread throughout almost all the Americas.
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“So, while it is correct to say that the known mosquito vectors of Zika virus are not present in New Zealand, it is misguided [and potentially dangerous] to assume that we do not have mosquito vectors capable of transmitting the virus”.
