You describe microcephaly as a “serious congenital malformation”, which risks confusing the public and causing needless distress to the families of children with small heads, irrespective of whether these are linked to Zika virus infection (see Nature 530, 5; 2016). In fact, 'microcephaly' simply means a small head and is not necessarily associated with intellectual disability, as is often assumed.

Microcephaly is a feature of hundreds of different conditions, but can also be seen in otherwise normal individuals (P. Merlob et al. J. Med. Genet. 25, 750–753; 1988; S. Ashwal et al. Neurology 73, 887–897; 2009).

This is not mere semantics. Investigations into the proposed link between Zika virus and birth defects (for which there seems to be little evidence at present) will need to include systematic assessment of all the possible causes of microcephaly in children thought to have been affected by the virus (C. G. Victora et al. Lancet 387, 621–624; 2016).