News Brief by Julia O'Gara
While Zika virus has been found in the breast milk, urine, and saliva of mothers and their newborns from crossing the placental barrier during pregnancy, it is unclear whether it has caused microcephaly.
Brazil has had 20 times the number of babies born in 2015 with microcephaly compared to years past at the same time that it has recorded a high number of Zika virus infections. However, like many birth defects, it has historically been linked to a range of factors including genetics, drug or chemical exposures, maternal nutrition during pregnancy, and other viruses such as herpes, HIV, or chikungunya which can also cross the placental barrier.
In this case, a team of investigators lead by Dr. Ana de Filippis of Oswaldo Cruz Institute in Rio de Janeiro, Brazil investigated two mothers who had been infected with Zika during their first trimester and whose fetuses had confirmed microcephaly found in ultrasounds around 22 weeks of pregnancy. The amniotic fluid sampled from both women at 28 weeks eliminated the possibility of other viruses capable of crossing the placental barrier, including ones carried by mosquitos; however, the fluid did test positive for Zika virus. Subsequent genetic analysis connected the Zika virus which the women had contracted with the strain that broke out in French Polynesia in 2013.
The Lancet. "Zika virus can cross placental barrier, but link with microcephaly remains unclear, evidence suggests." ScienceDaily. ScienceDaily, 21 February 2016. https://www.sciencedaily.com/releases/2016/02/160218060741.htm.