Zika Virus Infection as a cause of congenital brain abnormalities and Guillain–Barre Syndrome
Zika virus is a cause of congenital brain abnormalities, and is a trigger for Guillan-Barre syndrome
Unexplained clusters of rare but serious conditions require urgent assessment of causality. As of October 2016, 67 countries reported local transmission of zika virus, of which 27 reported cases of congenital brain abnormalities or both. This study aimed to provide a rigorous assessment of the causal relationship between Zika virus (ZKV) and (a) congenital brain abnormalities and (b) Guillain-Barre syndrome (GBS).
Three methods were employed: a modified version of Bradford Hills causality framework was used to define the relationship between ZKV and the two clinical outcomes, a systematic review to find evidence for causality framework, a panel of experts assessed the findings. For congenital brain abnormalities 72 studies were assessed and for GBS 36 studies were assessed. For congenital brain abnormalities, including microcephaly, more than half the relevant studies supported a causal association with ZKV infection in eight of 10 causality dimensions. For GBS, more than half the relevant studies supported a causal association in seven of ten dimensions (all except dose–response relationship, specificity, and animal experimental evidence). The expert panel concluded that ZKV is a cause of congenital brain abnormalities, and that ZKV is a trigger for GBS.