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Latest on Microcephaly in Brazil


About this time in 2015, Brazilian public health authorities began to receive reports of an unusual number of cases of a birth defect called microcephaly in newborns. It appears that the defect, with other serious defects, is associated with some pregnant mothers contracting a Zika viral illness. This illness was passed to their fetus and seems to have caused, or at least contributed to the development, of these neurological defects.

The latest report from Brazil’s Ministry of Health is for the period ending September 17, 2016. It includes data beginning November 8, 2015.

Reports of Microcephaly

A total of 9,514 reports of newborns with microcephaly have been received in the nine months. In that time, the Ministry altered the reporting requirements twice. Both times, the changes tightened the description and reduced the number of reports being received. The current reporting requirements match the clinical description offered by the World Health Organization.

The Ministry is also reviewing each report to determine if it meets the current criteria for microcephaly possibly related to Zika. Some 68 percent of the reports have been investigated and 4,535 have been discarded for one of two reasons. Either the diagnosis of microcephaly was incorrect or, if there was microcephaly, it was clearly not due to an infection. The latter group would include newborns with Downs Syndrome or Fetal Alcohol Syndrome, for example.

As of September 17, 1,949 cases of microcephaly have been confirmed to have been related to an infection. The last six weeks have seen an average 30 percent of investigated reports confirmed. The Ministry believes that all of these are due to a maternal Zika infection during pregnancy.

There have been 447 miscarriages or stillborn births reported. About half have been investigated. 146 of the 216 investigations revealed microcephaly in relation to a congenital infection. 85 of the investigations were not.

The Ministry estimates that 1.36 million Brazilians have contracted a Zika illness, 15.3 percent of the population.

In the last six months, 3,116 reports of microcephaly were received by the Ministry, an average of 120 new reports per week. The data released by Brazil does not detail the age of the reports being investigated so it is not possible to evaluate the accuracy of recent reports versus the oldest reports.

Clustering of Microcephaly Cases

The geography of microcephaly is worth noting. The majority of reports originate in the northeast region of Brazil. More importantly, 81 percent of the confirmed cases are from that region.
Brazil asks whether Zika acts alone to cause birth defects

“We suspect that something more than Zika virus is causing the high intensity and severity of cases,” says Fatima Marinho, director of information and health analysis at Brazil’s ministry of health. If that turns out to be true, it could change researchers’ assessment of the risk that Zika poses to pregnant women and their children.

There are many hypotheses about what might be going on. Marinho says that her team’s data, submitted for publication, hint that socio-economic factors might be involved. For example, the majority of women who have had babies with microcephaly have been young, single, black, poor and tend to live in small cities or on the outskirts of big ones, she says.


The events in Brazil cannot be viewed in a vacuum. Zika illnesses have appeared in many other parts of the Western Hemisphere. Of note are outbreaks in Colombia and Puerto Rico.


In Colombia, in 2016, there have been 632 cases of newborns with neurological complications. Of that total, 295 are under study. Zika with associated microcephaly has been confirmed in 42 patients and 200 cases have been discarded. (Total equals 537.) That is from a population of 5,883 pregnant women with confirmed Zika illnesses and an additional 12,604 with suspected illnesses.

Puerto Rico

Zika case distribution in Puerto Rico

Through September 22, 2016, Puerto Rico’s Department of Health reports 26,499 confirmed cases of Zika illness since January 1, 2015. There have been 2,106 pregnant women infected, and 36 percent of them have reported no Zika symptoms. Two cases of Zika-related birth defects have been reported.


Birth defects such as microcephaly that may be related to a Zika illness can be diagnosed before birth through various forms of imaging such as ultrasound and MRIs. Prenatal imaging is not conclusive, and examination 24 hours after birth is the standard to determine the existence of microcephaly. Zika first appeared in Puerto Rico in December 2015. Children exposed to Zika will begin being born in large numbers beginning in September 2016.

The Colombian experience is that 17 percent of investigated cases have been shown to be related to Zika. Brazil is about 30 percent.

It would be very useful to know how many women have delivered after contracting Zika, and how many women, in total, delivered in the same period. Unfortunately, all of the public health authorities are focused on Zika and all other data is either not being made public or is not being retained. It would also be useful to know how many cases of microcephaly are due to causes other than maternal Zika illness.

Some Causes of Microcephaly
CDC Boston Children’s Hospital Cleveland Clinic
changes in their genes an inherited defect in a gene Chromosomal disorders such as Down’s syndrome, Cri du chat syndrome, Trisomy 13, and Trisomy 18
Infections such as rubella, toxoplasmosis, or cytomegalovirus exposure to certain viruses – especially chickenpox, rubella (German measles) or cytomegalovirus Maternal viral infections such as rubella (German measles), toxoplasmosis, and cytomegalovirus
Severe malnutrition inadequate nutrition Maternal malnutrition
Exposure to harmful substances, such as alcohol, certain drugs, or toxic chemicals use of drugs or alcohol, abuse of prescription medications, exposure to toxic chemicals Maternal alcoholism or drug abuse, Mercury poisoning
untreated phenylketonuria (PKU) Uncontrolled maternal PKU
Maternal diabetes

The microcephaly “outbreak” in Brazil continues to baffle us with unanswered questions. Another six months may provide answers, or it may yield additional questions.

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