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Microcephaly and Zika

Is there an outbreak of microcephaly in Brazil? That is one of the first questions that ought to be asked when examining the topic of the potential effects of a prenatal Zika viral infection. Without knowing the preexisting rates of this serious yet usually rare birth defect, any recent change is impossible to detect. Unfortunately, data from public health authorities and medical educators is so varied that a conclusion may not be possible.

Each piece of data below will have a citation number, displayed in bold red, which refers to an ordered list at the bottom of this piece.


These tables use a variety of different sources with differing microcelphaly incidence rates to predict the “normal” number of microcephaly cases for both the United States and Brazil. [1/30/2016 7:22 pm – this paragraph added for clarification.]

Births [1]          2,953,597 [2]          3,988,076
Brazil, PER 10,000 [3] 0.5 148
CDC A, PER 10,000 [4] 1.0 295
CDC B, PER 10,000 [5] 2.0 591
ECLAMC, PER 10,000 [6] 1.98 585
CDC C, PER 10,000 [7]  591 2.0 798
CDC D, PER 10,000 [8]  3,544 12.0 4,786
Virginia DoH A, PER 10,000 [9]  1,181 4 1,595
Virginia DoH B, PER 10,000 [10]  1,772 6 2,393
Cleveland Clinic A, PER 10,000 [11] 347 1.18 469
Cleveland Clinic B, PER 10,000 [12] 476 1.61 643
Handbook of Toxicologic Pathology A, PER 1,000 [13] 1,772 0.6 2,393
Handbook of Toxicologic Pathology B, PER 1,000 [14] 4,726 1.6 6,381

The second table uses the above data from the United States, and its application to Brazil, to show the means and medians. I discarded the data from the highest incidence, 12:10,000 and the lowest, 0.6:1,000 before calculating. [1/30/2016 7:22 pm – I have corrected the mean and median calculations. I believe that removing the two highest values, CDC D and Handbook B, provides better data for these statistical values. I have also corrected a typo by changing the second Handbook entry to B from a duplicate A.]

Mean 1,023 2.57 1,382
Median 886 1.81 1,197


In a Jan. 26 article in Nature, Declan Butler explores the possibility that the increase in reported microcephaly cases in Brazil is unrelated to an outbreak of Zika viral illness and may even be non-existent. The article, titled Zika virus: Brazil’s surge in small-headed babies questioned by report, is based upon a report from the Latin American Collaborative Study of Congenital Malformations (ECLAMC) [6].

In the article, Butler reports that as of Jan. 27, Brazil had “4,180 suspected cases of microcephaly recorded since October.” The government had examined 732 of those, and had rejected 462, 63 percent, as false diagnoses. While the ratio of false diagnoses of 462:732 is unlikely to be the final result, it provides an additional set of data that can be analyzed in a limited way.

Using the 4,180 suspected cases as a starting point, the analysis suggests that 1,547 cases will be found to be properly diagnosed as microcephaly. That number is very uncertain but it is useful. If incidence rates other than those from the Brazilian government and the rates labelled CDC A and CDC B are used, 1,547 begins to look a lot like a normal number of cases.

ECLAMC notes in its report that the Brazilian authorities are using an unproven criteria for microcephaly. The government has changed the diagnostic criteria to reflect that all children with a head circumference of less than 33 cm. should be reported as a case of microcephaly.

Normal head circumference is known to vary by ethnicity. [15] Newborns in the United States have been found to have a larger head, on average, then those in the Third World. It is also noted that an exam and measurement of the skulls of a newborn’s parents is also warranted as the family may just be expressing a trait for a smaller than average skull.

More than one study has noted that the WHO charts vary from those produced by the CDC. “For children in industrial countries, the mean OFC is larger than that indicated in the WHO standard values, which are based on measurements taken from about 8500 children in Brazil, Ghana, India, Oman, and the USA.” [16] OFC is the abbreviation for occipital-frontal circumference.


Data exists that suggests that the number of confirmed cases of microcephaly in Brazil will be far lower than the number of reports. In addition, the actual number of cases of microcephaly per year in Brazil prior to the arrival of the Zika viral illness is less clear than it might be. It is impossible to draw a sound conclusion that the Zika outbreak has or has not added to the number of cases of microcephaly in Brazil.

The data is suggestive that the number of microcephaly cases will range, in a given 12 months, from normal to two or three times normal. It remains an issue of great concern but the hype seems to have far exceeded the threat.

Citations and Sources

  1. CIA World Factbook 2015 estimate
  2. U.S. National Vital Statistics Report Births:Final Data for 2014
  3. Schuler-Faccini L, Ribeiro EM, Feitosa IM, et al. Possible Association Between Zika Virus Infection and Microcephaly — Brazil, 2015. MMWR Morb Mortal Wkly Rep 2016;65:59–62. (historical incidence)
  4. ibid. (expected incidence – low)
  5. ibid. (expected incidence – high)
  6. Latin American Collaborative Study of Congenital Malformations (ECLAMC)
  7. CDC Facts about Microcephaly (low)
  8. ibid. (high)
  9. Virginia Dept of Health fact sheet Microcephaly (low)
  10. ibid. (high)
  11. Cleveland Clinic – Microcephaly in Children (low)
  12. ibid. (high)
  13. Editors Wanda M. Haschek, Colin G. Rousseaux, Matthew A. Wallig, Haschek and Rousseaux’s Handbook of Toxicologic Pathology, Third Edition, Volume One (Waltham: Elsevier, 2013) 2723. (low)
  14. ibid. (high)
  15. BAXTER, P. (2011), Head size: WHOse growth charts?. Developmental Medicine & Child Neurology, 53: 3–4. doi: 10.1111/j.1469-8749.2010.03847.x
  16. von der Hagen, M., Pivarcsi, M., Liebe, J., von Bernuth, H., Didonato, N., Hennermann, J. B., Bührer, C., Wieczorek, D. and Kaindl, A. M. (2014), Diagnostic approach to microcephaly in childhood: a two-center study and review of the literature. Developmental Medicine & Child Neurology, 56: 732–741. doi: 10.1111/dmcn.12425



  1. Adam – Yours is a long comment. I’ll just speak to a couple of items.

    I have a long history of criticizing Recombinetics and Dr Neiman. He has a conflict of interest with any comments about disease outbreaks since his firm markets software designed to track such outbreaks. He makes a lot of inflammatory statements and most, if not all, do not come true. So, poor track record and conflict of interest.

    There is no such thing as a mild case of microcephaly. A very few outgrow it or do not exhibit associated ills. The overwhelming majority suffer, and I mean suffer, from a variety of crippling and limiting conditions for as long as they live. About half die in utero or as a newborn.

    I agree that more needs to be done about public health, including internationally. I do begin by pointing the finger at national governments, such as Brazil, mired in corruption and incompetence, first.

    Dr. Chan is correct. There is no proven link between Zika viral illnesses and microcephaly in newborns. Correlation never proves causality.

  2. If you speak Brazilian Portuguese fluently you will know by doing the appropriate research that up until a week ago the number of newborns with Microcephaly in Brazil is upwards of 4400. And the statistics are probably being fudged. The Brazilian MOH has gone into damage control mode. As a pregnant woman in Brazil there is now a 1 in 120 chance that your baby will have Microcephaly. Prior to Oct. 2015 the chances of this terrible outcome in Brazil was 1 in 4000 and even then most cases of Microcephaly were mild. The current outbreak has seen many affected babies with a severe form of Microcephaly. Thus the current figures are off the charts.

    Remember as well that the lag effect may be in place now and that other countries in South and Central America soon, and very likely as well in the USA and other nations may also go down the disastrous Zika – Microcephaly route. What will various “rich, white, western” nations think of suddenly many babies are born within their borders with such a terrible condition ? How will the public handle this phenomenon ? It may not just be a case of “Oh well, it is affecting those poor brown women in Brazil, but I am safe…”

    Absolute vigilance from the hilltop is required now to see how these Zika waves pan out. Waves have already hit the shore…

    The situation is very, very serious. No-one should pay lip service to the threat.

    I repeat…As much high level co-operation as possible on the dis-ease front is required now. It is a case of “All hands on deck”.

    Zika is the new kid on the global dis-ease block. It has literally come out of nowhere. It is the most concerning right now, but Swine Flu, Bird Flu, MERS and Ebola are not far behind. Various dis-eases seem to take turns at popping up in the global “Whack a Mole” game. There is a way to get “on top” of the various viruses, which are types of fauna remember, once and for all. But it requires high level international co-operation.

    There is a proven link between the current Sth.American Zika virus strain and Microcephaly and Guillain-Barrè Syndrome !

    It is not merely conjecture, supposition or possibility as Margaret Chan said bizarrely on Monday.

    @WHO 12:45 CET Mon. 25Th Jan. 2016 Dr Chan: Although a causal link between Zika in pregnancy & microcephaly has not been established, the circumstantial evidence is worrisome (!!!)

    Henry L Niman PhD @hniman BeH815744 Full 2015 Zika Genetic Sequences From Brazil’s Evandro Chagas Institute + Microcephaly matches

    A gene sequences is like the DNA Code of the virus. A virus can be mathematically mapped for its properties. The virologists can analyse various viruses to see how they compare to others. This first sample LOCUS KU365777 shows that the Brazilian strain of the Zika virus has 10,663 nucleotide “bits” represented by the letters. The MERS virus gene sequence in comparison has about 30,114 nucleotide bits. All viruses are different. If even only 60 of these unique identifiers are different between strains that means some sort of mutation has occurred. An elaborate bomb device without a detonator is pretty much harmless if handled correctly. But add a little wick and a lit match to the contraption and you have a serious problem. What the full truth is with Zika now is super important to work out. Thus as much high level international co-operation is required to get “on top” of the dis-ease threat. This should have happened yesterday. A conference should be organized ASAP. An International Body must be empowered to do a number of things : 24/7/365 Oversight, Monitoring, Analysis of the Global Dis-ease Threat. Data Sharing. Gene Sequencing Analysis. Counselling/Warning. Recommending Interventions. Various Modalities. Public Awareness Campaigns. Management of Vaccine Research. On the Ground Campaigns. Follow Up etc. etc.

    “Complete Coding Sequence of Zika Virus from a French Polynesia Outbreak in 2013”

    The earlier analyzed French Polynesia Zika strain has 10,617 nucleotide bits. So the Brazilian strain of Zika is 46 nucleotide bits longer/bigger. Why ?

    The virus threats are like a series of waves on an ocean. They move back and forward and change in intensity and priority. Some can develop into a tsunami. But the waves can be managed if the nations co-operate. We should rule over the world of fauna, viruses are a type of fauna don’t forget, not the other way around. But as Louis Pasteur said…

    “Messieurs, c’est les microbes qui auront le dernier mot.”

    The Neglected Dimension of Global Security : A Framework for Countering Infectious-Disease Crises.

    Peter Sands, M.P.A., Carmen Mundaca-Shah, M.D., Dr.P.H., and Victor J. Dzau, M.D. January 13, 2016DOI: 10.1056/NEJMsr1600236

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