Two new studies seeking to determine how often Zika causes severe birth defects in fetuses have returned conflicting results, frustrating scientists' efforts to pin down how the virus works. Both studies are products of esteemed research teams and reported in high-quality journals.
The first study found that out of 125 Brazilian women infected with Zika, 46% of pregnancies were negatively affected by the infection. The second study, however, found that 6% of the 442 American women who tested positive for Zika and were included in the study had pregnancies that resulted in birth defects.
Despite these differences, the teams are not disputing each others' results, partially because other findings held across both studies. For example, both studies found that around 10% of fetuses infected in the first trimester ended up with microcephaly. In addition, the technical definition of and criteria for microcephaly vary from country to country. This and other inconsistencies in methodology mean that the greatest takeaway is perhaps that more research is still needed to understand Zika's effects, as the truth has been elusive thus far.
by Julia Daniel