Studies Underscore Zika Dangers for Fetuses

     (CN) — Two recent studies expanded the known symptoms of the Zika virus with evidence that the virus can result in body deformities and other abnormalities, even if the infected individual does not have microcephaly.
     Researchers from the Brazilian Ministry of Health and other institutions conducted one of the studies, which found that roughly 20 percent of the babies born with the Zika virus had normal sized heads — though they still may suffer from developmental delays or other defects.
     “Our study, which included all suspected cases of microcephaly in newborns in Brazil up to February (2016), discarded three out of five cases after a full investigation as most suspected cases ended up being normal newborn babies with small heads. However, one in five definite or probable Zika cases had head circumference values in the normal range,” lead author Cesar Victora said. “Therefore, the current focus on microcephaly screening alone is too narrow.”
     Zika’s potential connection to microcephaly, a congenital disorder that results in reduced head size and potential brain damage, was theorized for months by experts before several studies appeared to confirm the link.
     The Brazilian Ministry of Health set up a surveillance system for microcephaly following the 2015 Zika outbreak in northeast Brazil. Nearly 5,909 suspected cases of microcephaly were reported by Feb. 27, 2016, 5,554 of which were live births.
     The team reviewed 1,501 live-born cases of microcephaly from the Brazilian Ministry of Health’s surveillance system and recorded various characteristics, including gestational age, image findings and head circumference.
     They separated the cases into five categories based on the diagnostic certainty of Zika infection: definite, highly probable, moderately probable, somewhat probable, and discarded, meaning not deemed to be Zika.
     While researchers discarded 899 cases, 602 babies listed as definite or probable for a Zika infection also had small head circumference at birth, and their mothers were more likely to experience a rash during pregnancy. The babies were also four times more likely to die within the first week of life.
     “Our findings suggest that among pregnancies affected by Zika virus, some fetuses will have brain abnormalities and microcephaly, others will have abnormalities with normal head sizes, and others will not be affected.
     “A surveillance system aimed at detecting all affected newborns should not just focus on microcephaly and rash during pregnancy and should be revised, and examination of all newborns during epidemic waves should be considered,” Victora said.
     Rashes in late pregnancy were linked with brain abnormalities despite normal head sizes — development of the cranium primarily occurs by week 30, so babies can be born with normal sized heads but still suffer from brain damage.
     The findings validate concerns over Zika’s potential connection to brain damage in infants, according to the authors.
     “Although we believe that the underreporting of microcephaly cases is rare during the epidemic, newborns infected with the virus late in pregnancy may go unreported due to their head size being within normal range,” Victora said.
     Over 100 of the definite or probable cases had head circumferences within normal range and would have been left out of an analysis for Zika if smaller cutoffs had been used.
     The authors also cautioned that the findings may be affected by missing data and no specific cut-off point for head circumference.
     An second study on Zika — also published this past week in the journal The Lancet — documented the virus’ presence in the brain tissue of a deceased 2-month-old baby in Brazil, in the brain tissue of two newborns who died soon after birth, and in the placenta of two fetuses miscarried at 11 and 13 weeks gestation.
     The findings support theories that the virus is connected to various birth defects.
     Researchers from the Centers for Disease Control and Prevention analyzed tissues from the three post-mortem cases and the two placentas, and reviewed the symptoms of all five mothers.
     Zika virus antigens were detected in the neurons and glial cells — non-neuronal cells that support neurons in the central and peripheral nervous systems — of the three fatal cases. Analysis of brain tissue showed damage, cell degeneration, calcium deposits and cell death.
     The Zika virus was not detected outside of the central nervous system in the spleen, kidney, liver, heart or cartilage, but all three cases displayed a range of birth defects and brain abnormalities.
     Genetic analysis of the Zika samples show a close match to strains isolated in Brazil during 2015.
     The mechanism by which Zika may cause abnormalities is unclear, but the authors believe the abnormalities likely stem from the virus attacking the central nervous system to cause subsequent brain damage and muscle impairment.
     “Until now, there have been no reports of a mosquito-borne virus that could cause severe birth defects,” the study’s lead author Sherif Zaki said. “Further studies will now need to look at whether there is a link between birth defects and Zika virus infection during the second and third trimester of pregnancy, and understand the mechanism of transmission.”
     

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