Thanks to its worrying rise in prevalence and the potential consequences for unborn children, media coverage of the Zika virus has been ubiquitous. A recent case study described in PLOS Neglected Tropical Diseases adds to the level of concern.
The Zika virus is a mosquito-borne disease, first described in Ugandan monkeys in 1947 and Nigerian humans in 1954.
Most often, carriers of the virus are asymptomatic, and, if individuals do present symptoms, they generally pass within a week.
However, the virus has been shown to travel through the placenta from the pregnant mother to her unborn child. Concerns surrounding resultant birth defects have been mounting.
Because of the swift rise in Zika incidence rates, travel warnings have been issued for multiple countries in Central and South America, the Caribbean and parts of Oceania and Africa.
The World Health Organization (WHO) declared Zika a Public Health Emergency of International Concern on February 1, 2016.
As with any of the myriad of viruses carried by mosquitos, the only way of avoiding the disease is to avoid the vector.
But Zika utilizes the wings of Aedes albopictus and Aedes aegypti, both of which fly during the day, are unafraid of air-conditioning and thrive throughout much of the world. This makes avoiding them even more challenging.
Zika and microcephaly
The Zika outbreak in Brazil was first detected in early 2015; since then, there has been a steep increase in reported cases of microcephaly - babies born with a smaller-than-average head associated with neurological defects and seizures.
To date, 4,500 microcephaly cases have been reported in Brazil since the outbreak began. A much smaller number of cases (seven in total) have linked Zika to central nervous system (CNS) defects in fetuses who also died shortly after birth (fetal demise).
This week, another worrying case has been described by researchers led by Dr. Albert Ko, of the Yale School of Public Health in New Haven, CT, and Dr. Antônio Raimundo de Almeida, at the Hospital Geral Roberto Santos in Salvador, Brazil.
For the first time, non-CNS birth defects have been documented alongside fetal demise.
The case in question involves a healthy pregnant 20-year-old. She presented no Zika symptoms during the pregnancy, or indeed symptoms of any other mosquito-borne viruses. Additionally, tests for HIV, cytomegalovirus, rubella and hepatitis C all came back negative. She appeared healthy with no causes for concern.
Is Zika causing fetal demise?
During the 18th week of pregnancy, an ultrasound found that the fetus' weight was significantly lower than expected.
By the 30th week, the fetus had a range of defects. At week 32, labor was induced but resulted in a stillbirth. Laboratory tests later showed that the Zika virus was present in the fetus' tissue; the virus was the same strain that is currently running rife in the Americas.
In addition to microcephaly, the fetus showed hydrops fetalis, arthrogryposis and hydranencephaly. Hydrops fetalis involves a fluid buildup in compartments of the developing fetus; arthrogryposis is an abnormality of the joints, and hydranencephaly describes an almost complete absence of the cerebral hemispheres.
Dr. Ko explains the ramifications of these findings:
"These findings raise concerns that the virus may cause severe damage to fetuses leading to stillbirths and may be associated with effects other than those seen in the central nervous system."
Of course, the case study includes details of just one individual patient. Dr. Ko and colleagues call for "additional work [...] to understand if this is an isolated finding and to confirm whether Zika virus can actually cause hydrops fetalis."
The fact that around 73% of Zika infections do not produce symptoms compounds the problem. It is almost impossible to trace through a population; as the authors say, only future studies can confirm this new finding.
Medical News Today recently covered the earlier research that demonstrated that the Zika virus can indeed cross the placenta.