The link between Zika virus and the increase in microcephaly cases was first investigated because mothers who gave birth to children with microcephaly reported having had a rash, like the one in this figure, during their pregnancy. (“Zika.Virus.Rash.Arm.2014” by FRED – Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons )

When Zika virus (ZIKV) arrived in Brazil this year it was expected to be a weaker version of Dengue virus. However, when cases of microcephaly, a rare neurological disorder, skyrocketed in the northeast region of Brazil, Brazil’s Ministry of Health (SUS) began investigating if ZIKV might have anything to do with it.

Infants with microcephaly have an abnormally small head for their age and sex, and it is often associated with further developmental issues. Brazil has on average around 156 cases of microcephaly annually, but in 2015 alone there have already been 1,248 suspected cases. When there is an unexpected increase in the number of cases of such a rare disorder, epidemiologists focus on potential environmental causes. In this case, the Brazilian government has zeroed in on congenital ZIKV infection after mothers of infants diagnosed with microcephaly reported suffering a rash, which is one of the more distinctive symptoms of ZIKV infection, during their pregnancy.

The link between ZIKV and the increase in microcephaly cases was considered “highly probable” when ZIKV was found in the amniotic fluid of two pregnant women whose unborn-infants were diagnosed with microcephaly in utero. As of this Saturday (November 28th), SUS has reported ZIKV’s blame in the microcephaly surge as “confirmed,” after detecting ZIKV in the blood and tissues of a child born with microcephaly who passed away a few days after birth. More tests are necessary to firmly confirm that ZIKV is the causative agent of these cases of microcephaly, but the Brazilian government has already begun setting up strategies to contain ZIKV and to further understand how it might be causing neurological malformations in fetuses.

If ZIKV does cause microcephaly, an important question to ask is whether congenital infection with ZIKV has always been able to cause microcephaly or if this is a newly evolved consequence of the virus. Dr. Kleber Luz believes that while both explanations are possible, viral evolution is the less likely of the two. What’s more probable is that Zika virus has always caused an increased chance of microcephaly, but because the level of epidemiological surveillance varies from country to country, previous spikes may have gone undocumented.

Acknowledgements: Special thanks to Dr. Kleber Luz from Universidade Federal do Rio Grande do Norte (UFRN) – who first reported the arrival of ZIKV in Brazil -, for his time and expert commentary on this developing case.

Further Reading:
Official SUS statements on Zika Virus (both in Portuguese):
Confirmation of link between Zika virus and microcephaly
Latest update on microcephaly case (November 30, 2015)

Government says that link between Zika virus and microcephaly is “highly likely”

First report of autochthonous transmission of Zika virus in Brazil

Managing Correspondent: Fernanda Ferreira



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