Zika virus infection during pregnancy: what, where, and why?

On 1 February 2016 the World Health Organization declared a Public Health Emergency of International Concern following reports of large clusters of microcephaly and Guillain-Barre Syndrome associated with an increase in cases of Zika virus (ZIKV) infection in French Polynesia (2014) and Brazil (2015– 2016).1 The Committee emphasised that there was ‘... no public health justification for restrictions on travel or trade’ and the main interventions were to control mosquito populations and prevent bites in pregnant women. Why has this happened and how might it affect patients attending primary care in the UK? ZIKV was first isolated from a Rhesus monkey in Uganda in 1947.2 The following year it was identified in Aedes mosquitoes, which differ from malaria-transmitting Anopheles mosquitoes by biting during the day. ZIKV has been found throughout Africa and South East Asia where infection is asymptomatic or produces a mild febrile illness and rash which goes undiagnosed. The first outbreak was not recorded until 2007 when three-quarters of the population of Yap Island in Micronesia became infected.3 The current epidemic of ZIKV infection began in early 2015 in northeastern Brazil. Since then ZIKV transmission has been confirmed in 35 countries.4 One theory is that ZIKV was carried to Brazil by infected Pacific Islanders visiting an international canoeing event in Rio de Janeiro in August 2014. In September 2015 clinicians working in Pernambuco state noticed an increase in newborn babies with microcephaly. The Ministry of Health quickly established a register and within 3 months recorded 4180 suspected cases, including 68 deaths, compared to a total of 147 reports in …