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The Zika outbreak in Colombia has struck more than 65,000
people with symptoms of the tropical disease, including nearly
12,000 pregnant women, Colombian and U.S. public health
officials reported on Wednesday.
The report comes with some hopeful news about infections during
late pregnancy. So far, about 90% of the 1,850 Colombian women
infected in the the third trimester of pregnancy have borne
children, and none of those babies have the severe brain birth
defects that have become the signature of Zika virus in Brazil,
according to the report in the New England Journal of
“We are seeing a very large outbreak in Colombia,” study author
Margaret Honein of the U.S. CDC told BuzzFeed News. She called
the low birth defect numbers “somewhat reassuring news for
women in their third trimester,” but also noted that the
findings are preliminary.
“We really need to follow up on these children,” she said, to
look for Zika-related health problems later in life, such as
vision defects, hearing loss, or learning disabilities.
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In the past year, as
46 countries have reported first-time outbreaks of Zika
virus, starting with Brazil, the link between the tropical
disease and brain damage in infants has become a tragedy clear
both in the lab and in the maternity ward. The virus is
now linked to severe brain birth defects — most notably the
shrunken brain and skull syndrome called microcephaly — but
also to a rare paralysis syndrome called Guillain-Barre in
More than a million people have been infected in Brazil, which
has reported more than
1,551 confirmed cases of Zika-related microcephaly.
reported only seven as of last week, although experts
expect that number to grow in the next few months, as women
infected in the first and second trimesters have their babies.
In April, researchers reported brain
damage in Brazilian infants whose mothers had been infected
late in pregnancy, making the new study more surprising.
“We are largely seeing just women infected in the third
trimester in this study,” National Institute of Allergy and
Infectious Diseases (NIAID) director Anthony Fauci told
BuzzFeed News. The infant brain is much more fully developed in
the last trimester, so it makes sense that infection during
that period would be less dangerous, experts say.
observers have speculated that there’s something special
about Brazil — whether co-infection with dengue or better
reporting of stillbirths — that has led to its high rate of
Zika-related birth defects. But Fauci doesn’t think so. “We
should see in the next few months if there is really a
difference in microcephaly rates between countries,” he said.
Brazil has a population of 200 million people, four times more
than Colombia. That may also account for Brazil’s higher number
of microcephaly cases so far, along with the later arrival of
the virus in Colombia to infect pregnant women there.
“The unknown component is whether later stage pregnancy
infection such as in the third trimester results in more subtle
but still serious neurologic deficits,” Peter Hotez, an
infectious disease expert at the Baylor College of Medicine who
was not involved in the study, told BuzzFeed News. “It will
take further studies to sort this out.”
Four cases of Zika-related microcephaly were reported to
Colombian mothers in the study, which ended its data collection
in April. All were born to women who had no symptoms of the
virus, but were infected early in their pregnancy. Another 26
microcephaly cases in Colombia are still under investigation
for links to Zika, the study said.
Women were twice as likely as men to be infected by Zika in the
study, regardless of their age. That’s likely because women are
on high alert about Zika and may be more likely than men to
report symptoms, Nikolaos Vasilakis of the University of Texas
Medical Branch in Galveston told BuzzFeed News. Alternatively,
it could be because of men
transmitting the virus sexually to multiple partners, or
because women really do have a higher susceptibility to
symptoms. “We don’t know, but we are learning more about this
virus every day,” Honein said.
In January, Colombia
advised women to delay pregnancy for six to eight months to
try and avoid the outbreak during mosquito season. Past surveys
two-thirds of pregnancies in Colombia are unintended.