As Zika virus infections continue to spread, with cases reported in parts of Florida and southeast Asia, most people are familiar with the virus's most damaging effects: on the developing fetus during pregnancy. The most common consequence of infection is an underdeveloped brain, or microcephaly.
Not all babies who are exposed to the virus during pregnancy are affected by Zika; scientists currently believe that only about 10% to 20% of babies are.
When they are, however, they can show very different symptoms. In a report published in JAMA Neurology, researchers led by Dr. Amicar Tanuri at Universidade Federal de Rio de Janeiro in Brazil—a country with one of the highest numbers of affected babies born in the past year—say that microcephaly is only one of the many effects of the virus on fetal brains. Among the 11 babies studied, in whom Zika virus was confirmed in amniotic fluid and cord blood, three died within 48 hours after birth. Nine showed microcephaly, but two showed normal or even enlarged head circumference. All of the babies did, however, show signs of neurological abnormalities, including calcium lesions in parts of the brain, restricted growth and underdevelopment of the brain stem and cerebellum, which coordinates muscle movements.
"The general public is used to the term microcephaly for the babies congenitally infected by Zika. However, microcephaly is not the only thing that happens with fetal Zika infection,” says Tanuri. “This virus can disturb the normal development of the human brain by killing primary neural cells as well as delaying or modifying the movement of brain cells during development. If the lesions are very drastic the babies do not survive, and the ones that survive carry severe developmental or cognitive delays or deficits."
The data involves just a small number of cases, but it provides a more comprehensive picture of how the virus seems to target developing brain cells. The results highlight the need for women who are pregnant or planning to become pregnant to avoid areas with infected mosquitoes and to protect themselves from mosquito bites by covering exposed areas and removing any standing water, where mosquitoes like to breed, from their surroundings. There are no vaccines or treatments for Zika infection yet, but researchers are working on those, as well as studying whether a previous Zika infection can protect women by giving them a chance to produce antibodies against the virus.