EU Medical Surveillance Not Ready for Zika

(CN) — Medical surveillance systems in Europe could detect increases in Zika-related health conditions, but only if current practices and standards change and become uniform across member states.

In a study published Tuesday in the journal BMJ, researchers detailed how self-reporting and varying standards of congenital disorders that could result from a Zika infection — such as microcephaly — will make it challenging to determine if Europe is experiencing more cases of the mosquito-borne virus and the disorders it can cause.

Due to the small increases expected in Europe and inconsistent approaches to accounting for diseases and disorders that can stem from Zika infections, the researchers said existing surveillance systems in Europe will ultimately be insufficient.

The team reviewed the European Surveillance of Congenital Anomalies (EUROCAT) to determine potential variations between nations and registries.

They specifically analyzed reported cases of microcephaly — a condition that leads to babies being born abnormally small heads, potential brain damage and can also result in stillbirths — and how different nations and clinics have different standards for determining if an infant has the disorder.

For example, of the 16 registries that responded to a questionnaire distributed by the authors, seven registries used EUROCAT's definition of microcephaly: a reduction in the size of the brain with a skull circumference more than 3 standard deviations below the mean based on age, sex and ethnic origin. Three registries used a cutoff of 2 standard deviations, while five relied on the criteria used by individual clinics.

In a linked editorial, University of South Florida professor Russell Kirby — who was not part of the study — highlighted the need for consistent oversight and evaluation of potential cases of microcephaly.

"While birth defect registries perform a vital population health function, registers of pregnancies affected by Zika virus with follow-up of both mother and child must be established urgently to fully understand the natural course of the Zika syndrome and its impact on child growth and development," he said.

However, the lack of a consistent definition of microcephaly did not necessarily lead to more diagnoses of the condition at registries with more moderate standards.

Registries with the 3 standard-deviation cutoff reported a rate of 1.74 cases of the disorder per 10,000 births, while those with the less stringent cutoff had 1.21 cases per 10,000.

While the overall prevalence was 1.53 cases per 10,000 births, registries varied from 0.4 to 4.3 per 10,000, possibly due to different diagnostic criteria, variations between nations or a combination of both.

The authors also noted that the prevalence of microcephaly in Europe would need to increase by more than 35 percent in one year, or by 300 percent in a single registry, to be considered a statistically significant increase.

"While the Zika virus is an unlikely threat in much of Europe, the challenges for surveillance of birth defects should be addressed now to strengthen the quality and effectiveness of this essential public health function," Kirby said.

Colder weather conditions and a limited presence of the Aedes aegypti mosquito — the primary vector of Zika — make Europe less at-risk for outbreaks. But many other nations could experience active transmission in the near future.

A recent study found that nearly 2.5 billion people could be exposed to or ultimately develop the virus.

The number of locally transmitted Zika infections in southern Florida reached 70 on Tuesday, after six new confirmed cases were reported.

Meanwhile, Kirby noted that the United States has the same lack of reporting standards that concerns the European study researchers.

"Ironically, the National Birth Defects Prevention Network in the United States made the decision to discontinue annual reporting of microcephaly by state because of extreme variability in state-level prevalence reports," Kirby said.

Follow @SeanDuffyCNS

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