Skeptophilia (skep-to-fil-i-a) (n.) - the love of logical thought, skepticism, and thinking critically. Being an exploration of the applications of skeptical thinking to the world at large, with periodic excursions into linguistics, music, politics, cryptozoology, and why people keep seeing the face of Jesus on grilled cheese sandwiches.

Wednesday, December 20, 2017

The final word on Zika

One of the posts that earned me the most hate mail was one I did a while back on the Zika virus, wherein I suggested that what the scientists were telling us -- namely, that the Zika virus was the cause of the recent upsurge in microcephaly in infants -- was the truth.

The alternate hypotheses -- that the birth defect was due to exposure to the insecticide pyriproxyfen, widely used to control the Aedes aegypti mosquito (which is the vector not only for Zika, but for chikungunya, yellow fever, and dengue fever), or even more outlandish, that the condition was caused by being bitten by genetically-modified Aedes mosquitoes -- I suggested were scientifically unsound and extremely unlikely borderline conspiracy theories.  The genetically-modified Aedes, in fact, were released as a method for reducing mosquito populations and therefore the spread of the diseases they carry, but that carried little weight with the people for whom "GMO" means "tool of the evil scientific establishment and Big Pharma for killing people and/or turning them into mindless automata."

[image courtesy of the Wikimedia Commons]

Well.  You'd have thought I was suggesting carpet bombing Fern Gully or something.  I was called credulous and brainwashed, and those were the generous responses.  Others suggested I was a stooge of the scientific establishment or a shill for Big Pharma, and was deliberately spreading misinformation to fool the general public into thinking that the scientists actually care about humanity.  As such, I was complicit in any damage they did, which according to some people who wrote to me, might include the extinction of the human race.

I didn't bother trying to disabuse my detractors of these opinions.  For one thing, I've found that people who believe something that fervently are seldom convinced by rational discourse.  All my objections would have done is convince them that they were onto something, despite the fact that recent trips to my mailbox have turned up zero Shill Payments to me from Big Pharma.

But time passed and the furor died down, and the more rabid of my readers went on to find other things about me to criticize.  But I just stumbled a couple of days ago across an article in the online science magazine Stat to the effect that, lo and behold...

... a recent exhaustive study has shown that microcephaly is due not to insecticides or GMO mosquitoes, but to the Zika virus itself.

Look, it's not like I wouldn't admit it if I was wrong.  It's been known to happen, and as much as it isn't exactly pleasant, I'll be up front about it and eat crow if necessary.  But here, the new study, conducted by a team of fourteen Brazilian doctors and scientists and published in the highly respected British medical journal The Lancet, is unequivocal.  The authors write:
We screened neonates born between Jan 15 and Nov 30, 2016, and prospectively recruited 91 cases and 173 controls.  In 32 (35%) cases, congenital Zika virus infection was confirmed by laboratory tests and no controls had confirmed Zika virus infections.  69 (83%) of 83 cases with known birthweight were small for gestational age, compared with eight (5%) of 173 controls.  The overall matched odds ratio was 73·1 (95% CI 13·0–∞) for microcephaly and Zika virus infection after adjustments.  Neither vaccination during pregnancy or use of the larvicide pyriproxyfen was associated with microcephaly.  Results of laboratory tests for Zika virus and brain imaging results were available for 79 (87%) cases; within these cases, ten were positive for Zika virus and had cerebral abnormalities, 13 were positive for Zika infection but had no cerebral abnormalities, and 11 were negative for Zika virus but had cerebral abnormalities...  We provide evidence of the absence of an effect of other potential factors, such as exposure to pyriproxyfen or vaccines (tetanus, diphtheria, and acellular pertussis, measles and rubella, or measles, mumps, and rubella) during pregnancy, confirming the findings of an ecological study of pyriproxyfen in Pernambuco and previous studies on the safety of Tdap vaccine administration during pregnancy.
"Importantly, this article provides the first evidence that exposure to the insecticide pyriproxyfen and vaccines administered during pregnancy were not associated with an increased risk of microcephaly," wrote Federico Costa and Albert Ko (of the Oswaldo Cruz Institute and Yale University School of Public Health, respectively) about the recent study.  "The biological plausibility of these two rumored causes was always weak in any case."

So that should be that, but of course you know it won't be.  Studies like this one don't convince the naysayers and conspiracy theorists; all they do is move the scientists who conducted it into the "evil and untrustworthy" column.  You have to wonder what would convince these people.  My guess is nothing.  As I've so often commented, you can't logic your way out of a position you didn't logic your way into.

I'm already bracing myself for another tsunami of hate mail, but hell, that's why I do what I do, right?  As punk rocker John Lydon put it, "If you're pissing people off, you know you're doing something right."

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