Yesterday I posted about Declan Butler's Nature News & Comment article Report questions size of surge in Brazil's microcephaly cases. Today I've read the ECLAMC report on which it's based.
I did so in part because a reader asked why, if the US with 300 million people has 25,000 microcephaly cases yearly, Brazil with 200 million shouldn't have a proportionate number of cases--somewhere around 17,000 cases?
That in turn sent me on a search through various American and European health websites. I found the 25,000 number on just one site, the Foundation for Children with Microcephaly, which also says "Microcephaly affects 2-2 1/2% of the entire population." Perhaps so, but I didn't find corroboration on the 25,000 yearly statistic.
The CDC was far less specific, estimating the microcephaly rate at from 2 to 12 cases per 10,000 live births. Given the approximately 4 million births in the US in 2013, that would mean 800 to 4,800 microcephaly cases.
Brazil's annual live births in the period 2010-2015 were 3,073,000. At a rate of 2 per 10,000 births, that would mean 614 yearly microcephaly cases; at 12 per 10,000 it would mean 3,684...very close to the numbers we now hear from the Brazilian Ministry of Health as an appalling increase in cases.
The ECLAMC authors argue that the growth in microcephaly numbers is a "seek and ye shall find" effect: the cases were alway there but not recorded as such. (And I recall late last year that Brazil's medical authorities were in a fuss about just how many centimeters would take a baby from microcephaly to normal.)
They also argue that if the EUROCAT numbers on microcephaly in Europe are accurate (2.85 per 10,000 live births), Pernambuco's 1,153 microcephaly cases out of 147,597 births in 2015 are 25.6 times the European baseline...meaning that 100% of pregnant Pernambuco women must have caught Zika last year to explain 1,108 of Pernambuco's cases.
I'll let you review the ECLAMC report's 13 pages at your leisure and judge whether its arguments make sense—including its proposal for a case-cohort study in some Brazilian state where Zika circulation is increasing. The authors suspect that many other fetal infections (collectively known as STORCH) may be involved, but that remains to be seen. Their arguments seem to me highly testable, and should be tested.
Acquitting Zika of causing microcephaly may cause enormous relief to pregnant women everywhere, especially in Brazil (and enormous embarrassment to Brazil's Ministry of Health and international agencies like PAHO). Latin American tourism and travel will also survive, shaken but unharmed.
But Zika doesn't get out of jail free. It's still charged with triggering unusually high numbers of Guillain-Barré syndrome cases, and in several countries that have yet to report a spike in microcephaly.
To confirm or refute the Zika-microcephaly connection, and the Zika-Guillain-Barré connection, we'll need to conduct an enormous surveillance and testing operation coupled with a massive Aedes-extermination program. We'll likely find more unwelcome news about mosquito-borne viruses, but also reduce the numbers of dengue, chikungunya, yellow fever, and Zika cases—not to mention identifying and reducing the causes of many other fetal deformities, around the world.
