A study published in the The Lancet on Feb. 6, 2016, reported that, prior to 2015, the number of reported suspected cases of microcephaly in infants born in Brazil had remained “consistently below 200” each year.1 Between mid-2015 and Jan. 30, 2016, the number of suspected cases of microcephaly reported totaled 4,783.1 Thus, in just half a year, the total number of suspected microcephaly cases was 2,291% higher, compared to previous annual totals. Therein lies the source of the whole microcephaly scare.
Going from 200 suspected cases of any disease or illness in one year to nearly 24 times that amount in half a year would certainly be enough to qualify as a serious epidemic and justify a healthy level of concern, even fear. It is important to note, though, that, of those 4,783 suspected cases of microcephaly reported to the Brazilian government, only 1,130 of them had “completed clinical, laboratory, and imaging examinations” to confirm the diagnosis of microcephaly. After all the results of the lab tests and imaging exams were analyzed, only 404 (36.2%) of the 1,130 were actually classified as “confirmed cases” of microcephaly.1
So, that little detail dramatically changed the degree of the “epidemic.” In other words, by the beginning of February 2016, it was known that microcephaly was not an epidemic of 4,783 cases, but rather one of 404 confirmed cases. But by then Brazil’s President Dilma Rousseff—who has now been suspended from her office and is facing impeachment proceedings for allegations of financial irregularities and several corruption scandals2—had already publicly blamed the microcephaly cases on the Zika virus and declared “war” on the Aedes aegypti mosquito that carries it.3
On Feb. 12, 2016, Brazil’s Minister of Public Health Marcelo Castro, MD confirmed that the microcephaly cases were due to the Zika virus transmitted by the Aedes aegypti mosquito.4 By then, Dr. Castro was citing 5,079 “suspected” cases of microcephaly, even though only 462 cases had been “confirmed” as microcephaly.4 Naturally, the media kept highlighting the higher number of suspected cases, rather than the lower number of confirmed cases or the fact that an additional 765 cases had been determined to be misdiagnosed and were not microcephaly after all.4
This seemed to be a case of a government declaring war on a mosquito and declaring a public health emergency because of a massive Zika virus epidemic that was not nearly as massive as was being publicized, thus prematurely fueling an international panic. As Brazil prepares to host the Olympics in August, some have speculated that politics was involved in creation of the Zika virus panic to deflect public attention away from the internal crisis facing the current government.5
Even so, a fight seems to be breaking out in the medical community as more than 150 doctors are alleging the Zika virus is such a big threat that they have sent a letter to the World Health Organization (WHO) calling for the Olympics to be postponed or held in another location.6
One of the reasons for the discrepancy between the number of suspected cases of microcephaly and the confirmed is that it’s not always clear just by looking at the size of an infant’s head whether the child has microcephaly or is simply a normal child with a small head. So there may be many suspected cases that, after careful examination, turn out not to be actual cases of microcephaly. The study in The Lancet alludes to this.
Although there is evidence of an increased number of cases of microcephaly in Brazil, we show that the number of suspected cases relied on a screening test that had very low specificity and therefore overestimated the actual number of cases by including mostly normal children with small heads.1
Additionally, the confirmation for microcephaly in Brazil became more confusing in December 2015 when the medical criteria for diagnosing microcephaly was revised.
On Dec. 8, 2015, the Ministry of Health in Brazil revised the case definition for suspected microcephaly in newborn babies and reduced the head circumference criterion in term newborn babies to less than or equal to 32 cm. On Jan. 21, 2016, the Pan American Health Organization. (PAHO) proposed the use of fixed cutoffs of 32·0 cm and 31·6 cm for term boys and girls…1
Before Dec. 8, 2015, in order to be classified as having microcephaly, a newborn baby in Brazil had to have a head circumference measuring less than or equal to 33 centimeters. After Dec. 8, 2015, a Brazilian infant could be diagnosed as having microcephaly only if the child’s head circumference was less than or equal to 32 centimeters. After Jan. 21, 2016, the diagnosis criteria dropped yet again to a head circumference of 31.6 centimeters.1
That is why at the end of January 2016 there were only 404 confirmed cases of microcephaly in Brazil. Although that was still a significant number of cases, it was not anywhere close to the 5,000-plus figure of microcephaly cases being reported in the media around the world and creating such a stir. It’s unclear what the final tally of confirmed cases of microcephaly in Brazil will be for 2015.
Until that information is clear, it will not be possible to accurately measure the extent of the epidemic. And even then, it will be difficult, because it is possible that, as a result of the increased media attention given to microcephaly during the second half of 2015, Brazilian doctors were more apt to actively look for suspected cases of microcephaly than they would have been in years past. Consequently, cases of microcephaly in Brazil prior to all the government and media attention over the past year may have been under-reported prior to 2015.
As a Public Radio International report on Zika statistics pointed out in January 2016:
The authorities and media are repeatedly comparing the thousands of suspected microcephaly cases to typical averages of 150 or so per year. That number is about right, as far as known cases go: Brazil’s Health Ministry sent GlobalPost a table showing that reported microcephaly cases from 2010 to 2015 ranged from 139 to 175 annually. But here’s the thing: The Brazilian government in late 2015 put out a bulletin urging pediatricians and clinics to be on the lookout for microcephaly and to be sure to report cases. Since then, the number of reported cases has spiked. It is very possible, as the report Nature highlighted points out, that there has been significant over-diagnosis of microcephaly. It’s also possible, in a country criticized for its record-keeping, that many clinics were not thoroughly reporting microcephaly cases prior to 2015.7
So, was there a dramatic spike in the incidence of microcephaly among infants born in Brazil last year? It is hard to say. What is certain is that the actual number of cases of that birth defect was nowhere close to what the Brazilian government and the media consistently highlighted in the first few months of the international panic, and so you have to wonder how different the story would have turned out had the reporting been more accurate and less sensationalistic.
Would we still be witnessing the birth of the Zika industry that is taking shape today?8
1 Gomes Victora C, Schuler-Faccini L, Matisjasevich A, Ribeiro E, Pessoa A, Barros FC. Microcephaly in Brazil: how to interpret reported numbers?. The Lancet Feb. 6, 2016.
2 Anderson JL. Dilma Rousseff and Brazil’s Horrible Year. The New Yorker May 25, 2016.
3 Eisenhammer S. Brazil’s Rousseff declares war on mosquito spreading Zika virus. Reuters Jan. 27, 2016.
4 Cáceres M. Brazil at Odds With WHO and CDC on Zika-Microcephaly Link. The Vaccine Reaction Feb. 18, 2016.
5 Watts J. Dilma Rousseff suspended as senate votes to impeach Brazilian president. The Guardian May 12, 2016.
6 Axon R. 150 health professionals call for Olympics in Rio to be postponed or held in another location. USA Today May 27, 2016.
7 Carless W. The sketchy numbers behind Brazil’s Zika crisis. Public Radio International Jan. 29, 2016.
8 Cáceres M. Birth of the Zika Industry. The Vaccine Reaction May 16, 2016.