New research supports association between Zika virus and microcephaly
pharmafile | March 16, 2016 | News story | Medical Communications, Research and Development | Lancet, Zika virus, french polynesia, microcephaly, outbreak
Using data from the 2013-14 outbreak of Zika virus in French Polynesia, new research in The Lancet has further supported the link between the infection and microcephaly. They estimate that the risk of the neurological abnormality is about 1 for every 100 women infected with Zika virus during the first trimester of pregnancy.
Although the data focuses only on the outbreak in French Polynesia, it is hoped that quantifying the risk using existing data will help to inform the broader public health response, particularly with the current outbreak in South America. Although the risk of microcephaly associated with Zika virus is relatively low compared to other maternal infections, according to the researchers, it is still statistically significant given the risk of Zika virus infection is particularly high during outbreaks.
Babies born with microcephaly are born with abnormally small heads, and the condition is associated with a reduction in brain volume, often leading to intellectual disabilities, speech impairment and behavioural issues.
The researchers used mathematical and statistical modelling to estimate the expected number of microcephaly cases under different assumptions about the risk of the condition from Zika virus infection. They used data on the total number of cases, the weekly number of consultations for suspected Zika virus infection, blood tests confirming the presence of Zika virus antibodies piost-outbreak, and the total number of births during the outbreak.
Comparing these models to the number and timing of actual cases of microcephaly, they found that the data indicated that the scenario where the first trimester of pregnancy was associated with an increased risk was the most consistent. They were able to estimate the risk of microcephaly as 95 in 10,000 women (or approximately 1 in 100) infected with Zika virus in the first trimester of pregnancy.
Professor Arnaud Fontanet, co-author of the study, and from the Institut Pasteur, comments: “Data from French Polynesia are particularly important since the outbreak is already over. This provides us with a small, yet much more complete dataset than data gathered from an ongoing outbreak. Much more research is needed to understand how Zika might cause microcephaly. Our findings support WHO’s recommendations for pregnant women to protect themselves from mosquito bites.”
Dr Laura Rodrigues, London School of Hygiene & Tropical Medicine, writes in a linked comment: “The finding that the highest risk of microcephaly was associated with infection in the first trimester of pregnancy is biologically plausible, given the timing of brain development and the type and severity of the neurological abnormalities. Further data will soon be available from Pernambuco, Colombia, Rio de Janeiro and maybe other sites.
“The fast production of knowledge during this epidemic is an opportunity to observe science in the making: from formulation of new hypotheses and production of new results that will provide confirmations and contradictions to the refinement of methods and the gradual building of consensus.”
Sean Murray
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