About one in 100 women infected by the Zika virus in early pregnancy may be at risk of having a baby with microcephaly, according to a new study of an epidemic that occurred in French Polynesia. 
 
 
 
 The study, published in the Lancet medical journal, offers further evidence that the virus is implicated in microcephaly – a condition in which babies’ brains do not develop properly, resulting in abnormally small heads. 
 
 “Our analysis strongly supports the hypothesis that Zika virus infection during the first trimester of pregnancy is associated with an increased risk of microcephaly,” says Dr Simon Cauchemez, co-author of the study from the Institut Pasteur in Paris. “We estimated that the risk of microcephaly was 1 in 100 women infected with Zika virus during the first trimester of pregnancy. The findings are from the 2013-14 outbreak in French Polynesia and it remains to be seen whether our findings apply to other countries in the same way.” 
 
 Although the risk that they calculate through mathematical modelling – 1% – is low by comparison with a virus such as rubella which causes birth defects in 50% of women infected in early pregnancy, the attack rate of the Zika virus itself is very high. There may be other co-factors in Brazil, where the rise in cases of microcephaly has triggered an international alert from the World Health Organisation. But if the findings from French Polynesia are applicable, “in Latin America right now we are speaking about relatively small risks which apply to a very large population of pregnant women,” said Professor Arnaud Fontanet, co-author of the study, from the Institut Pasteur in Paris. 
 
 The rate of 1% is lower than that found by a previous study earlier this month. Researchers in Rio de Janeiro, Brazil, enrolled 72 women who had a rash – the most identifiable symptom – and who tested positively for Zika. Out of 42 healthy women who agreed to an ultrasound examination, 29% had a foetus with microcephaly or some other sort of congenital malformation. 
 
 The Institut Pasteur scientists, however, were searching past data from the French Polynesia Zika outbreak in 2013-14 specifically for microcephaly – a small head accompanied by evidence of calcifications in the brain. Their study, they say, had the advantage of very good, complete data. Congenital abnormalities were always reported. They found eight microcephaly cases in the two years, seven of which followed the Zika epidemic. The other they consider their baseline – one case a year would have been the norm for the French Polynesian population and is the equivalent of two per 10,000 live births, a similar prevalence to that of Europe. 
 
 They constructed a number of mathematical models to attempt to explain the increase during the Zika epidemic. The best fit was with infection of the mother by the virus in the first trimester of pregnancy. 
 
 The researchers set out to look at microcephaly and not the larger number of congenital malformations that were reported during the epidemic in French Polynesia. “It may well be that infection during the second trimester or the third trimester could lead to a different type of congenital malformation,” Fontanet told the Guardian. The first trimester is crucial for the development of the brain, “but if you infect later you can imagine there might be other malformations”. That would fit with the study of pregnant women in Rio de Janeiro. 
 
 Writing in a linked comment, Dr Laura Rodrigues from the London School of Hygiene and Tropical Medicine, said: “The finding that the highest risk of microcephaly was associated with infection in the first trimester of pregnancy is biologically plausible, given the timing of brain development and the type and severity of the neurological abnormalities.” 
 
 More research is needed however, she said. “Further data will soon be available from Pernambuco, Colombia, Rio de Janeiro, and maybe other sites … The fast production of knowledge during this epidemic is an opportunity to observe science in the making: from formulation of new hypotheses and production of new results that will provide confirmations and contradictions to the refinement of methods and the gradual building of consensus.” 
 
 
 
 Dr Melissa Gladstone, senior lecturer in paediatric neurodisability at the University of Liverpool, welcomed the research, but cautioned: “Unless direct links are made and/or full investigations of babies are undertaken to exclude other causes and to identify Zika infection in infants, it will be difficult to entirely link Zika with microcephaly,” she said. “Furthermore, we may have a long way to go in terms of knowing whether there are more subtle effects of Zika virus on infants and children in the long term which span beyond microcephaly to developmental and learning difficulties.” 
 
 Dr Derek Gatherer, a lecturer in biomedical and life sciences at Lancaster University, said the study helped scientists begin to think about defining a risk period during pregnancy, with major implications likely for travel advice for pregnant women travelling to affected areas. ||||| Brazilian babies born with a birth defect blamed on the Zika virus may also often have serious eye problems on top of brain damage, doctors reported Tuesday. 
 
 They found troubling eye defects in more than a third of the babies they examined in December, and say they ruled out other known potential infections that could have caused them. 
 
 Fundus Photographs of a 20-Day-Old Infant. The right eye has optic disc hypoplasia, peripapillary nasal atrophy, and an excavated nasal round lesion with a hyperpigmented halo, with a colobomatous-like aspect (A), and the left eye has optic disc hypoplasia, peripapillary nasal atrophy, and a retinal nasal lesion with a similar pattern (B). Bruno de Paula Freitas, MD, et al of the Federal University of São Paulo, Brazil / The Jama Network 
 
 The discovery adds to a growing body of evidence that the babies suffering microcephaly in Brazil have a serious and unusual pattern of brain and nerve damage. Doctors and scientists are working to measure just how bad the surge in microcephaly cases in Brazil really is, and whether Zika is directly causing it. 
 
 But officials at the Centers for Disease Control and Prevention say there’s no doubt something unusual is happening with microcephaly in Brazil, and it coincides with the arrival and explosive spread of Zika virus. 
 
 And it’s clear that, whatever has happened to the newborns in Brazil with brain damage, the effects will be lifelong and and severely disabling. 
 
 The findings only involve 29 infants, but they were carefully examined and have had a battery of tests, Dr. Bruno de Paula Freitas and colleagues at Federal University of São Paulo in Brazil reported. 
 
 The babies all had microcephaly, defined as having a head that’s 32 cm or less in circumference. When babies have such small heads, their brains are also underdeveloped. 
 
 “Twenty-three of 29 mothers (79.3 percent) reported suspected Zika virus infection signs and symptoms during pregnancy, 18 in the first trimester, four in the second trimester, and one in the third trimester,” the team wrote in the Journal of the American Medical Association’s JAMA Ophthalmology. 
 
 “Of the 29 infants (58 eyes) examined ocular abnormalities were present in 17 eyes (29.3 percent) of 10 children (34.5 percent).” 
 
 “We are concerned that these lesions are going to have an effect on vision as the babies get older." 
 
 Dr. Lee Jampol, a professor of ophthalmology at Northwestern University’s Feinberg School of Medicine, in Chicago, said it’s not clear how much the lesions will affect the children's vision as they grow. 
 
 “It is very difficult to measure visual function in a newborn baby,” Jampol told NBC news. “We are concerned that these lesions are going to have an effect on vision as the babies get older. There is a lot of testing that not been done yet.” 
 
 On top of the lesions, found in several parts of the babies’ eyes, the damage done by the microcephaly itself could affect their vision, Jampol said. 
 
 “If you look at some of the images, you will see little clumps of black pigment. Those shouldn’t be there,” said Jampol, who with his colleague Dr. Debra Goldstein wrote a commentary on the JAMA Opthalmology paper. 
 
 Some of the babies have scarred retinas, and that will affect their vision as they grow, he said. 
 
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 It’s not unexpected. The eyes are an extension of the brain, Jampol said. Other viruses known to damage the brains of developing babies, such as West Nile virus, cytomegalovirus and rubella, can also affect the eyes. 
 
 And sometimes adults infected with dengue virus, a close relative of Zika, also suffer damage to the retina, Jampol said. 
 
 “We don’t know with 100 percent certainty that the virus is causing retinal lesions, but we think it likely,” Jampol said. 
 
 Dr. William Dobyns, a geneticist at Seattle Children's Hospital, has said his examinations of some brain scans of kids with microcephaly from Brazil show “very severe, destructive injury to the brain". 
 
 Related: Answers to Your Questions About Zika 
 
 The CDC has advised pregnant women to stay away from countries where Zika is newly spreading; the World Health Organization has declared the outbreak of microcephaly to be a global public health emergency and Brazilian authorities are working to eradicate as many of the mosquitoes that carry Zika as possible. 
 
 Scientists are also teaming up to see what connection there is between Zika and microcephaly and whether the infection is causing a paralyzing neurological condition called Guillain-Barre syndrome in some patients. 
 
 There’s no specific treatment and no vaccine for Zika, which was considered an extremely mild infection before Brazil called the alarm last year. About 80 percent of people who are infected don’t even know it. Symptoms in the other 20 percent are usually mild and include a rash and fever, 
 
 One thing De Paula Freitas and colleagues noticed was that the mothers they’ve interviewed seem not to have had many instances of conjunctivitis, or pinkeye, which was considered a classic symptom of Zika. ||||| Daniele Santos feeds her baby, Juan Pedro, 2-months-old, in their living room on February 3, 2016 in Recife, Brazil. (Photo: Mario Tama, Getty Images) 
 
 A fetus infected with the Zika virus during the first three months of pregnancy has about a 1% to 13% risk of developing microcephaly, an abnormally small head usually caused by incomplete brain development, according to new estimates from the Centers for Disease Control and Prevention. 
 
 The CDC created a mathematical estimate of the microcephaly risk, based on reports from French Polynesia, which experienced a Zika outbreak from 2013 to 2013, as well as in the Brazilian state of Bahia, where Zika cases have been diagnosed since last year. 
 
 The study is important, because it can help doctors counsel pregnant women about the risks to their babies, said Peter Hotez, dean of the National School of Tropical Medicine at the Baylor College of Medicine in Houston. Pediatricians and health systems across the Americas also will have to prepare to care for babies with extensive disabilities. 
 
 Even if only 1% of Zika-infected babies develop microcephaly, that could overwhelm the health systems of developing countries that aren't equipped to care for severely disabled children, said Amesh Adalja, a senior associate at the Center for Health Security at the University of Pittsburgh Medical Center. Dengue is common in Brazil and throughout much of Latin America and the Caribbean. 
 
 Although Zika was first identified in a monkey in 1947, doctors first linked it to microcephaly only in 2015, after a large outbreak in Brazil. 
 
 The new report suggests that it's possible the virus could have been capable of causing microcephaly in the past, but that earlier outbreaks were too small for relatively rare events such as microcephaly to be noticed. 
 
 During the Zika outbreak on the Micronesian island of Yap, for example, a microcephaly rate of 1% to 13% would have resulted in zero to four cases, according to the CDC report, published Wednesday in The New England Journal of Medicine. 
 
 The increase in microcephaly cases in French Polynesia, which had a Zika outbreak in 2013 to 2014, was so small that doctors didn't even notice it at the time. Researchers only detected the increase this year, after the Brazil epidemic prompted them to go back and take a closer look at women's medical records. Although 31,000 people sought medical attention for the Zika virus, doctors found just eight cases of microcephaly — three in babies and five in pregnancies that were aborted. 
 
 It's not clear why microcephaly seems so much more common in Brazil, Hotez said. Brazil's Ministry of Health has confirmed 1,434 cases of microcephaly, according to a statement released Tuesday. Brazilian officials have said there could be up to 1.5 million cases of Zika in that country. 
 
 Hotez said it's possible that Zika virus has mutated in a way that makes it more likely to cause microcephaly. Or, it's possible that something about the environment of Brazil or the health of women there make them more likely to deliver babies with birth defects. 
 
 Scientists are also trying to figure out if women who have had other mosquito-borne infections, such as dengue virus, might be more likely to give birth to babies with birth defects, Adalja said. 
 
 Authors of the CDC report note that microcephaly could be only one of a range of birth defects caused by Zika. Doctors caring for babies with microcephaly have diagnosed a variety of eye problems that could lead to blindness. 
 
 And in a Brazilian study of 88 women published in March, ultrasounds found major abnormalities in 29% of the fetuses from women who tested positive for Zika, but none of the women without Zika infections. Women were exposed to the Zika virus between the sixth and 35th week of pregnancy, according to the study, also published in The New England Journal of Medicine. 
 
 Although some of the babies in that study had microcephaly, others had restricted growth in the womb; poor development of brain structures; calcifications in the brain, which signal places where tissue has died; abnormal amniotic fluid levels; or abnormal blood flow in the fetal brain, umbilical cord or placenta, according to the study. Two fetuses in the March study were miscarried and two were stillborn. 
 
 Although Zika is the first mosquito-borne virus known to cause birth defects, doctors have known for decades that viruses such as rubella, or German measles, can cause microcephaly and other serious problems. About 21% of babies infected with rubella develop microcephaly, Adalja said. Congenital rubella syndrome, which can include blindness, deafness and intellectual disabilities, has been eliminated in the U.S. because of the measles-mumps-rubella vaccine. 
 
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– A month after confirming Zika causes birth defects, CDC researchers say there is a "substantial" risk that a pregnant woman will have a baby with a birth defect if infected with Zika during her first trimester. More specifically, the risk for microencaphaly is 1% to 14% depending on the scenario, reports the AP. The range is wide given that research into the disease is relatively new. For the study, scientists analyzed data from 400 babies diagnosed with microcephaly—in which babies are born with abnormally small heads—in the Brazilian state of Bahia between July and February. Because the study focused exclusively on microcephaly in a single Brazilian state, "these numbers are probably only the tip of the iceberg," says a UCLA professor. One notable quirk: the bigger the outbreak, the better the odds are of having a healthy baby—because more women would be exposed before becoming pregnant and perhaps develop immunity. When the outbreak is small, the risk rises to the 14% level. An earlier study out of Brazil put the risk of Zika-related birth defects and fetal death at almost 30%, though one based on a Zika outbreak in French Polynesia put the risk of microcephaly at 1%. But even a 1% risk could be devastating in developing countries, where there are limited care options for disabled children, a health expert tells USA Today. A separate study published Wednesday notes three Brazilian infants with microcephaly showed eye problems not linked to Zika before, including retinal lesions, hemorrhaging, and abnormal blood vessel development, per a release. (The number of pregnant women with Zika in the US has nearly tripled.)