Epidemic Of Zika-Linked Microcephaly Fails To Materialize In
Colombia
Causal Mystery
Deepens
Nine months have now passed since the peak of the Zika
epidemic in Colombia and the expected surge of birth defects has yet
to appear. After over 2000 cases of microcephaly were reported during
Brazil’s epidemic, experts were predicting that Colombia would see as
many as 700 babies born with serious neurological deformities. Yet
Colombia has reported only 47 cases of microcephaly to date, despite
experiencing over 100,000 cases
of Zika
infection (second only to Brazil) including 20,000 pregnant women.
While this discrepancy is most glaring in Colombia, the trend seems to
be holding true throughout the Americas where the Zika epidemic has
led to only modest increases in microcephaly outside of Brazil. The
following graphic from the Washington Post illustrates the
disproportionate rate of Zika-related microcephaly in Brazil relative
to other countries in the region1.
Co-factors
The missing cases of microcephaly in Colombia are not the first clue
that the causal link between Zika and birth defects may not be as
simple as first thought. Researchers and experts have been exploring
the idea that additional cofactors are interacting with Zika virus
infection to cause the high rates of severe microcephaly seen in
Brazil since last summer when the Brazilian government launched an
official probe to investigate the unusual geographical distribution of
microcephaly cases within Brazil. Almost 90% of reported cases of
microcephaly in Brazil were clustered in a small portion of the
northeastern corner of the country, leading many to suspect that Zika
alone could not be the cause of such a drastic increase in birth
defects (covered previously in the July issue of The Epi Monitor2).
While the Brazilian data alone are fairly compelling, the fact that a
massive spike in microcephaly has not followed the epidemic across the
rest of South and Central America provides further support for the
idea that cofactors are likely involved. As Ernesto Marques,
an epidemiologist from the University of Pittsburgh working with
researchers in Brazil recently told the Washington Post, “Now we’ve
settled on Zika as the smoking gun, but we don’t know who pulled the
trigger.”
Columbia For Answers
Experts are now hoping that Colombia may provide clues as to what
these other factors may be. The single biggest difference between the
epidemics in Brazil and Colombia may simply be the numbers involved.
Colombia is a much less densely populated country with a total
population of less than 25% that of Brazil. In addition much of
Colombia’s population lives at high altitude where there are fewer
mosquitos, while nearly all of Brazil’s population lives at low
altitudes where Zika carrying mosquitos thrive. Zika appeared as early
as 2014 in Brazil and circulated for some time before health officials
even became aware of it. The disease can be difficult to diagnose with
symptoms resembling other diseases endemic to the region, raising the
possibility that Brazil may have experienced many more cases of Zika
than is currently thought. By the time Zika spread to Colombia the
health system was more prepared with a system already in place to
thoroughly track and confirm suspected cases.
Cultural and Policy
Factors
These differences seem unlikely to fully explain the large discrepancy
in rates of microcephaly between the two countries, leaving some to
suggest that social policies may be minimizing the effects of the
epidemic in Colombia. Colombian officials believe that given the
chance to witness the effects of Zika on newborns in Brazil, many
Colombian women may have aborted fetuses showing signs of brain
abnormalities. For instance, the vice minister for public health,
Dr. Fernando Ruiz, said he believes it is “very possible” that
abortions have decreased the microcephaly rate in Colombia. In Brazil,
abortions are allowed only in cases of rape, incest or when necessary
to save the mother’s life. Illegal abortions are difficult to obtain
and the timing of the epidemic meant that for many women it would have
been too late to get the necessary ultrasounds and diagnosis in time.
In contrast, abortion is legal in Colombia in the case of a severely
deformed fetus as a means to protect the mental health and well-being
of the mother. Women now typically get three ultrasounds during a
pregnancy giving them much greater opportunity to diagnose
developmental abnormalities early in pregnancy. Most abortions in
Colombia are induced by a pill that can be prescribed by any doctor or
easily obtained illegally. While official reports do not show an
increase in abortion numbers, many women are told to go to the
hospital after taking the pill where they appear to have had a
miscarriage. Interestingly, the director of Colombia’s National Health
Ministry, Dr. Martha Lucia Ospina told the Washington Post in
July that Colombia was experiencing an 8% increase in miscarriages as
reported on fetal death certificates.
Dr.
Ruiz also believes the government policy enacted in December asking
women to delay pregnancy by 6 months has contributed to the lower
rates of microcephaly in Colombia. Unlike some other countries in the
region, where governments received pushback for asking women to wait 2
years to try to conceive, Dr. Ruiz feels that some Colombian women
felt that a 6 month delay was reasonable. If he is correct, government
statistics may show a decrease in birthrate when they are released
next year. For the time being, global health officials will track new
cases of microcephaly as babies are being born in countries where Zika
arrived much later (the first baby with Zika-linked microcephaly was
born in Puerto Rico
just weeks ago) and continue to search for the potential cofactors
that may explain vast discrepancies in microcephaly cases seen so far.
1.
https://tinyurl.com/hbcvpgn
2.
https://tinyurl.com/j58dthc
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