5 thoughts on “Study: Zika and the Risk of Microcephaly”

  1. The WHO claims an incidence rate for microcephaly of ‘one in several thousand’ http://who.int/mediacentre/factsheets/microcephaly/en/
    This requires Poisson statistics, in which the uncertainty is approximately 0-200% of the observed incidence.
    A incidence of ‘anywhere from 0 to 4 extra cases per 10,000 live births’ is statistically insignificant.

  2. The problem I have with this data is still that we are still not looking at the total births – only the cases of microcephaly. The classic case that lost keys are always found under the light – because that is the only place you are looking!

    There is no null hypothesis testing here: It starts from the assumption that zika is the cause of some portion of microcephaly cases, and then simply uses the correlation of estimated zika infections with (presumably) case numbers of affected births. The numbers of cases are still far too low to determine whether there is any increase in microcephaly from zika infection.

    This is especially relevant in developing countries where surveillance and reporting are in their infancy and have only started since the zika outbreak – there is quite simply no reliable baseline on incidence to make any assumptions on causality. Additionally, all of the post-outbreak surveillance is focussed on cases of microcephaly and looking for some kind of symptom which “could be explained” by a zika infection. In Brazil, there is follow-up with (I presume) a test for viral RNA or antibodies, but they don’t appear to be reporting negative cases – only confirmed and “yet-to-be-confirmed”.

    Furthermore, I have yet to see anybody reporting data on zika infection/presence in non-affected births – it is just assumed from the (highly innaccurate) infection rate estimates.

    It is all still too much of a beat-up for me. Maybe I am too cynical, but I don’t think panic helps anybody – except those who have an axe to grind or some kind of vested interest.

  3. Statistically insignificant, no effort to design a good study…

    But we need billions of dollars, and the Republicans are heartless bas..rds for questioning.

    Never let a crisis go to waste.
    Never let a day go by without a crisis.

  4. As tragic as Zika is, the same mosquito that transmits it is the same vector that transmits Dengue and yellow fever.

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