America's North Shore Journal

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Zika, microcephaly and all the fuss


map showing countries reporting Zika in circulation

WHO map showing countries reporting Zika in circulation

The onslaught of Zika stories in the media continues while the science lags. Searching “Zika” on Google News produces 86,500,000 results. Despite the coverage, there are still no firm estimates of the number of Zika viral illnesses as well as other key indices. Brazil continues to report an outbreak of microcephaly but the normal incidence of that birth defect has not yet been established.

Various groups are urging the Roman Catholic nations of Latin America to change their laws concerning birth control and abortion. Some national governments are urging women not to have sex for up to two years. The U.S. Centers for Disease Control and Prevention (CDC) suggests that pregnant women and those planning to become pregnant avoid travel to countries where Zika is circulating. The World Health Organization (WHO) has declared an Public Health Emergency of International Concern.


Microcephaly in the United States

Microcephaly is a birth defect. The CDC states:

Microcephaly is not a common condition. State birth defects tracking systems have estimated that microcephaly ranges from 2 babies per 10,000 live births to about 12 babies per 10,000 live births in the Unites States.

How many microcephaly cases occur in the United States, based on that statement? In 2014, there were 3,988,076 births, according to the CDC. That calculates to a range of 798 to 4,786 microcephaly cases for 2014.

A textbook titled Fetal Medicine: Basic Science and Clinical Practice, by Charles H. Rodeck, Martin J. Whittle, published in 2009 states that the incidence of microcephaly is between 1:8500 births and 1:6250 births. That suggests a range of 469 to 638 cases for the U.S. in 2014.

Confused? Twining’s Textbook of Fetal Abnormalities, by Anne Marie Coady, Sarah Bower, published in 2014 states that “the birth incidence of microcephaly is about 1 per 1,000.” That gives the U.S. 3,988 microcephaly cases in 2014.

Gene Dx, who bill themselves as the DNA diagnostic experts, have a fact sheet on microcephaly.

The general incidence of microcephaly at birth varies from 1.3 to 150 per 100,000 live births, depending on the population and the applied SD threshold to define microcephaly.

That estimate gives the United States a range of 52 to 5,982 microcephaly cases in 2014.

Even more estimated incidence rates can be found at an earlier report on this site Microcephaly and Zika, published Jan. 30.

Microcephaly in Brazil

There is no established incidence rate for microcephaly for the United States, or worldwide. That being said, can an estimated normal incidence rate for Brazil be determined? Possibly, and perhaps with more certainty that that for the United States.

A paper titled Microcephaly in northeastern Brazil: a review of 16,208 births between 2012 and 2015 was published on the World Health Organization site on Feb. 4. The authors looked at a large number of births in ParaĆ­ba. The births were categorized using three different criteria sets for microcephaly, and a combined set of all three.

Depending on the criteria utilized, in this sample, from 4% to 8% of kids born between 2012 and 2015 had microcephaly.

The study suggests that the incidence being reported by the Brazilian public health authorities is under-reporting the actual occurrence of microcephaly. In just the one Brazilian state, the study suggests that there were between 1,105 and 4,652 cases. That represents between two and eight percent of live births. These cases pre-date the appearance of Zika viral illnesses in Brazil.

As for the reported cases from Brazil, the WHO notes in their Feb. 5 situation report that the Brazilian authorities have received 4,783 reports of microcephaly since Oct. 2015. The authorities have examined 1,113 of those reports. 709 of those cases have been discarded as incorrectly diagnosed as microcephaly. Some 23 percent of the reports have been examined and 63 percent of those were rejected as not being cases of microcephaly.

If the ratio of 63:100 continues to hold for the reported microcephaly cases in Brazil, 1,769 cases of the 4,783 reports, will be found to actually be microcephaly.

Editorial Comment

Do the numbers of confirmed microcephaly cases in Brazil represent an increase from the normal incidence of that condition? Or, are they finally being noticed due to the coincidental appearance of Zika viral illnesses? If Zika is responsible, why are the large case numbers only being reported in Brazil?

More study is needed, and sooner rather than later. If a risk to unborn children exists from Zika viral illnesses, that needs to be firmly established. If the situation in Brazil is simply a matter of the authorities finally recognizing a serious medical condition in newborns that has been there all along, then the alarmist rhetoric by the CDC, national governments and pro-abortion advocates needs to be dialed back.

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