The answer to your question of whether there is "anything
more definitive than anecdotal evidence" depends upon
what exactly you mean by "anecdotal", the CDC description
notwithstanding.
A better question to ask might be whether there is a
measurable correlation between mothers Zika infection
status and whether their recent births showed microcephaly.
The answer apparently is "yes" but in public health situations
such as this, the question remains as to whether the
correlation is spurious or causal. At least one article has
addressed this issue; see:
http://www.sciencedirect.com/science/article/pii/S1286457916000083
However, others appear to believe that there is a definite
causal relationship as represented by a letter by physicians
dealing with mother with children with microencephaly; the
reference is:
Oliveira Melo, A. S., Malinger, G., Ximenes, R., Szejnfeld, P. O.,
Alves Sampaio, S., & Bispo de Filippis, A. M. (2016). Zika virus
intrauterine infection causes fetal brain abnormality and microcephaly:
tip of the iceberg?. Ultrasound in Obstetrics & Gynecology, 47(1), 6-7.
NOTE: I have a PDF of the letter.
A search of scholar.google.com for "Zirka virus" and "micoencephaly"
produces only 89 hits (two of which are provided above). One
will have to determine the quality and validity of the sources.
A major problem here, as in other cases involving public health, is
that the issue of whether the Zika virus is causing microcephaly
is a relatively new phenomenon and is based on observational
and correlational data. It is too soon to have experimental studies
with appropriate controls -- it is unclear what animal model one
would use given that one could not use humans (remember, we
still do not have true experimental data showing that cigarette
smoking cause illnesses in human; the experimental studies
involve animals while the human studies involved correlational
analysis).
One also has to ask why is this question being asked? Is it
because of purely intellectual curiosity or is one attempting a
risk analysis of the phenomena for the purpose of making
policy recommendations, such as having pregnant women
not going to areas where mosquitoes with Zika virus are known
to exist. The former point can take its own sweet time in
coming up with an answer while the latter needs an answer
yesterday because if there really is a causal relationship,
people need to change their behavior and other areas of
research (e.g., Zika vaccines) need to be started immediately.
So, ultimately, the question becomes "how much of a gambler
is one?" In the face of uncertainty, how risky is one willing to be?
-Mike Palij
New York University
[email protected]
On Mon, 01 Feb 2016 12:11:42 -0800, David Thomas wrote:
Dear Tipsters
There seems to be a panic being fueled by various news media that the
mosquito-borne zika virus is responsible for causing babies to be born
with
microcephaly, especially in Brazil. The best I can tell is that the
evidence of
this relationship is only anecdotal at this point. The CDC website
(http://www.cdc.gov/zika/disease-qa.html ) says the following:
"There have been reports of a serious birth defect of the brain called
microcephaly (a condition in which a baby's head is smaller than
expected when
compared to babies of the same sex and age) and other poor pregnancy
outcomes
in babies of mothers who were infected with Zika virus while pregnant.
Knowledge of the link between Zika and these outcomes is evolving . . ."
Has anyone seen anything more definitive than anecdotal evidence?
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