PARIS: Two studies of newborns in Zika-stricken Brazil yielded meager clues Wednesday about the mysterious workings of the virus, and prompted researchers to call for better tests to identify brain-damaged babies. Some infants with brain abnormalities may not be diagnosed because they have normal-sized heads instead of the tell-tale small skulls of those born with Zika-linked microcephaly, said one of the papers published by The Lancet. More than 100 babies who had “definitely or probably” been infected with Zika in the womb, turned out to have normal-sized heads in a recent study, researchers said. The skull is fully developed by about week 30 of pregnancy, which lasts some 40 weeks. This meant that “newborns infected with the virus late in pregnancy may go unreported due to their head size being within normal range,” said study co-author Cesar Victora of the Federal University of Pelotas. Also, many of the affected infants’ mothers had not had the pregnancy rash sometimes indicative of Zika infection.