How Does Zika Differ from Other Congenital Infections?

David A. Schwartz, MD, MS Hyg, FCAP, clinical professor of pathology at Medical College of Georgia, Augusta University, explains how congenital infection with Zika virus differs from congenital infection with other viruses.

Interview Transcript (slightly modified for readability)

“When we look at other infectious agents that can be transmitted from pregnant women to their fetuses, things like sexually-transmitted diseases, like syphilis, other viral diseases that we call cytomegalovirus, or rubella, some bacterial diseases, such as Listeria (Listeria is the reason [that] when you’re pregnant you’re not supposed to eat poorly cooked meat or cheeses), we generally see a pattern of inflammation in the placenta. Inflammation means that there are these white blood cells, or inflammatory cells, that are infiltrating the placenta and potentially causing damage. With Zika virus, this is not what we’re seeing. It appears that the Zika virus is able to go from the maternal to the fetal circulation, really causing almost no inflammation at all.

What it does seem to cause, is a certain cell-type in the placenta, that we call the Hofbauer cell, which is a macrophage, (and a macrophage is a Pac Man-like cell that’s normally present in the placenta that eats things; it helps digest waste, it helps pick up fluid) to multiply and proliferate. Our work has shown that, in fact, in these placentas, it is these macrophages, these Hofbauer cells, that actually are infected with the Zika virus. We’ve actually labeled these cells and shown that in babies who are born with congenital Zika virus syndrome, when we look at their placentas, these specific cell types still contain the virus at the time of birth.

In some cases, this could be over 10 weeks after mom develops symptoms of the virus. So, it appears as if Zika virus can persist in the fetus’s placenta long after mom develops her initial signs and symptoms. It’s a fascinating finding, and yet, it doesn’t really seem to elicit an inflammatory response.”