A recent study by the CDC showed that Zika virus RNA can persist and replicate in placentas and fetal brain tissue for more than seven months after the mother is first infected with the virus. This finding sheds light on why mothers with mild Zika infections can nevertheless give birth to babies with severe defects, or lose their pregnancy altogether. Furthermore, findings that the virus can persist and replicate in an infant's brain after birth raise questions about the prognosis for apparently healthy babies born to mothers infected with Zika during pregnancy.
In addition, the study provides a mechanism for the virus infecting the fetal brain. The study found that Zika infects Hofbauer cells, migratory placental immune cells. These cells may help transport the virus to the fetus, enabling it to proliferate in the brain tissue and affect development.
The study also confirmed earlier findings that the first trimester of pregnancy is the most dangerous time for the fetus to be infected. The study subjects with major adverse effects or death had all been infected in the first trimester.
Zika is an emerging virus from the family Flaviviridae, which also includes yellow fever, Hepatitis C, and dengue. It is an enveloped positive-strand ssRNA virus that usually causes a mild syndrome in adults but can be teratogenic in pregnant women.
by Julia Daniel