Scientists say the only way to stop Zika from spreading is with a effective vaccine. There are few treatments for microcephaly, a birth defect that causes babies to be born with small heads and neurological problems for the remainder of the child's life.
Puerto Rico and several other nations have seen huge spikes in the number of cases of microcephaly in the past two years as Zika has spread.
A research team at Stanford University announced today that it has discovered how the Zika virus disrupts the normal development of neural cranial crest cells, which are responsible for the growth of the skull and face.
"Zika can affect development of the skull, but also disrupts the communication between the crest and the developing brain," said Catherine Blish, associate professor of medicine at Stanford University.
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The finding, reported today in the journal Cell Host & Microbe, offers a possible understanding of why children born with the virus can have smaller-than-average skulls and disproportionate facial features. Curing the birth defect is still a remote possibility.
"You can't undo the development that has been done, but you can treat certain symptoms if you understand the reason for the symptoms," said Rachel Greenberg, a graduate student at Stanford and a co-author on the new paper. "If you understand that multiple tissues are affected, you don't just treat as only the brain is being infected."
There are several promising vaccine candidates in the works, but each one has different potential risks for pregnant mothers, according to Fauci, who is publishing a paper in today's New England Journal of Medicine outlining a strategy for the vaccine trials.
Fauci and colleagues say that vaccinating women of childbearing age and their sexual partners is the best approach. If it works, vaccinating children could be an option in the future. Randomized controlled clinical trials are the preferred approach to Zika vaccine testing because of regional variations in Zika incidence. They are also considering so-called "challenge models" where healthy volunteers are purposely bitten by a Zika-infected mosquito (half with a vaccine and half without) and carefully monitored for their response.
"The design of the trial needs to take into account there are a lot of things we do not know about Zika," Fauci said. "We want to make sure that it's safe for a large number of normal people."