Zika infection found in newborns without microcephaly
Damaging effects of Zika infection in newborns might not be evident until infant develops
The Zika virus can cause devastating brain defects in newborns with microcephaly, but also in babies with normal-sized heads and those born to women infected late in pregnancy, Brazilian doctors say.
In Wednesday's issue of the journal The Lancet, researchers said that of 602 babies born in Brazil with definite or probable Zika cases one in five had head circumferences in the normal range.
Dr. Cesar Victora of the Federal University of Pelotas in Rio Grande do Sul, Brazil, and his team say the current focus on screening for microcephaly or small head circumference alone is too narrow.
"We should not equate Zika congenital infection with microcephaly," Victora said in an interview from Washington. "We could well have many babies with normal head size who are affected. We will need to think about other exams to screen these babies, such as improving the diagnostic test we have for Zika and also possibly in areas that are undergoing an epidemic, doing ultrasound of the brains of these babies as soon as they are born."
The epidemic in the worst-hit northeastern regions of the country peaked in November 2015.
While the current season is cooler and mosquitoes aren't reproducing in Brazil, public health authorities continue to advise pregnant women to avoid travel to countries with Zika outbreaks. Countries in South Asia, the Western Pacific Islands, and South and Central America also have outbreaks.
A second wave in Brazil's southeast will likely result in the birth of affected babies starting in September, Victora said.
Accurate prenatal test essential
In a journal commentary published with the research, Brazilian experts Dr. Jorg Heukelbach of the University of Ceara and Dr. Guilherme Loureiro Werneck of the University of Rio de Janeiro said what is needed most is a better test for Zika infection.
"The development of an accurate [blood] test that could be incorporated into routine prenatal care will be essential, and its validation a research priority," the pair wrote.
Victora's study also suggests that in 30 per cent of babies who are affected with the syndrome, their mothers did not report a rash and likely had asymptomatic infections.
Rashes in the third trimester of pregnancy were associated with brain abnormalities despite normal head sizes, the researchers said.
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A second study published in the same issue adds to the evidence that Zika infection in pregnancy can cause a range of birth defects, such as constricted limbs and brain abnormalities.
The researchers examined autopsied tissues from two newborns with microcephaly who died shortly after birth, one baby who was two months old and two placentas from spontaneous abortions to fill in some pathology details.
Dr. Julie VanSchalkwyk, head of obstetrics and gynecology at B.C. Women's Hospital in Vancouver, said the latest findings wouldn't change her recommendations. The province has reported two travel-related Zika cases in pregnant women.
"I think what is most important is to realize ultrasound findings alone cannot either rule in or rule out Zika infection and that we really need to look at this infection as something that may be identifiable in the setting in the pregnancy, or it might even be postpartum as the infant develops that we start to see these effects, so followup is really important."
Victora said that in Brazil the affected families need a lot of support for babies who don't move their hands and legs much because of their constricted limbs and often cry out. Doctors, nurses and psychologists are trying to ensure babies are stimulated to try to minimize the effects, but it is a challenge for the country's health-care system.
Most people who have Zika virus illness have mild symptoms. The Public Health Agency of Canada advises precautions for travellers heading to countries with Zika virus outbreaks to avoid contracting the illness from mosquitoes and sexual partners.