Tuesday, September 6, 2016

The politicization of an epidemic: Zika virus and microcephaly

Every day for the past several months, Politico Pulse Check host Dan Diamond has posted a "Zika Virus update" on his Twitter account stating the number of days since the White House requested emergency funding to combat the epidemic (currently 211), how much Congress has appropriated in response ($0), and the number of Zika cases in the U.S. and its territories (currently >16,000). That there has been no funding response even as the virus continues to spread within the continental U.S. is testimony not only to longstanding Congressional gridlock, but to the politically charged nature of a sexually transmitted disease that can cause deformed babies, and therefore raise the issue of abortion. The Senate will vote today on a Republican-controlled bill that is identical to one that failed in late June due to Democratic objections over legislative "riders" stripping funds from the Affordable Care Act and Planned Parenthood. This vote has as much chance of succeeding as the earlier one did: zero. Both parties know this; they're just going through the motions. As a result, no new federal funding will be made available for disease surveillance or prevention, including the development of a vaccine.

As readers know, I get outraged whenever politics trumps science, especially when patients will suffer the consequences. But this story doesn't stop with the U.S. Congress. A potentially devastating piece of misinformation is circulating online that despite months of public health warnings, infection with the Zika virus is not responsible for Brazil's epidemic of microcephalic and otherwise brain-damaged babies. Instead, the story claims, the real culprit is the insecticide pyriproxyfen, which is manufactured by a Japanese affiliate of the widely reviled American biotech and agriculture company Monsanto. Supporters of this claim cite out of context a preliminary report published in the New England Journal of Medicine in June showed an extremely low rate of microcephaly in Colombia; of 12,000 women who were reported to be infected with Zika, none had given birth to a microcephalic baby. This finding is contrasted to Brazil, where pyriproxyfen was used to treat drinking water to kill mosquito larvae.

The key omission here is that most of the women in the Columbian study were still pregnant at the time the study was published. In fact, the only thing that the study's authors felt confident enough to conclude about the data was that Zika infection during the third trimester of pregnancy did not seem to be associated with microcephalic newborns, a finding that made sense given what is known about critical stages of fetal neurologic development. It was subsequently confirmed by a study of Brazilian and French Polynesian live births that reported "a strong association between the risk of microcephaly and [Zika] infection risk in the first trimester and a negligible association in the second and third trimesters." This study estimated that Zika infection raises the risk of having a baby with microcephaly from 2 in 10,000 (0.02%) to between 1 and 13%.

So what is keeping the pyriproxyfen hypothesis alive, a full six months after officials from the World Health Organization first shot it down? You guessed it: politics. Pro-life groups who worry about physicians advising Zika-infected pregnant women to abort their babies are apparently seizing on this misinformation to further muddy the waters of counseling, even though one could argue based on real data that the vast majority of Zika-infected babies will be fine anyway. Environmental groups, on the other hand, can't resist another opportunity to attack Monsanto.

How could this misinformation harm patients? Less insecticide in the air and water means fewer opportunities to control the mosquitoes that transmit Zika virus. Women who are even a little bit confused about the real cause of these birth defects might neglect to take mosquito-avoidance precautions or disregard the CDC's travel advisories. (And absent Congressional action, the CDC is rapidly running out of funding to deliver appropriate public health messages.) I am pro-life, I oppose abortion and capital punishment, and I believe that protecting the environment is a moral imperative. But I also believe in science. A public health crisis of brain-damaged babies is bad enough. Making it worse by twisting the facts to serve one's politics is nothing less than despicable.

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