Study
confirms Zika causes brain birth defects, questions
remain
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[September 16, 2016]
By Kate Kelland
LONDON (Reuters) - Early results from a
crucial case-control study in Brazil have confirmed a direct causal link
between Zika virus infection in pregnant women and the brain damaging
birth defect microcephaly in their babies, scientists said on Thursday.
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But while preliminary findings from the first 32 cases involved in
the study confirm causality, the researchers said, the true size of
the effect will become clear only after full analysis of all 200
cases and 400 controls.
The study, published in The Lancet Infectious Diseases journal, was
requested by the Brazilian health ministry to investigate the causes
of the microcephaly epidemic that the World Health Organization
(WHO) declared an international public health emergency earlier this
year.
The outbreak of Zika, a mosquito-borne disease, was detected last
year in Brazil, where it has been linked to more than 1,700 cases of
microcephaly, a birth defect marked by small head size that can lead
to severe developmental problems. The virus has since spread rapidly
through the Americas and Caribbean.

While the WHO and other disease experts had said there was strong
scientific consensus that Zika and microcephaly were linked,
evidence until now has been largely circumstantial.
MISSING PIECE OF JIGSAW
Laura Rodrigues, a professor at the London School of Hygiene and
Tropical Medicine who worked on this study, said its results were
"the missing pieces in the jigsaw" proving the link.
The research followed and compared pregnancies that resulted in
healthy babies with those that resulted in cases of microcephaly -
looking for signs that the Zika virus is passed onto fetuses who
develop the defect.
It covered all babies born with microcephaly delivered in eight
public hospitals in Brazil's north-eastern Pernambuco State between
January 15 and May 2 this year. For each case, two controls were
added. These were the first two babies born the following morning
without microcephaly in one of the hospitals.
After taking samples and conducting brain scans, the researchers
found that 41 percent of mothers of babies with microcephaly tested
positive for Zika infection in blood or cerebrospinal fluid samples,
compared with none of those whose babies did not have microcephaly.
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A high proportion of mothers of both microcephaly and non-microcephaly
babies also tested positive for another mosquito-borne virus, dengue
fever, as well as other infections such as herpes, rubella and
toxoplasma.
"Our findings suggest Zika virus should be officially added to the
list of congenital infections," said Thália Velho Barreto de Araújo
of Brazil's Pernambuco University, who also worked on the research
team. "However, many questions still remain to be answered -
including the role of previous dengue infection."
Rodrigues warned that preliminary analyses should be viewed with
some caution, since they can overestimate the strength of a link.
"When complete, the study, along with other ongoing research, will
provide vital information on any role co-factors might have in the
epidemic," she said.
(Editing by Ralph Boulton)
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