Use of infectious disease surveillance reports to monitor the Zika virus epidemic in Latin America and the Caribbean from 2015 to 2017: strengths and deficiencies

Objectives To summarise the occurrence of congenital Zika syndrome (CZS) in Latin America and the Caribbean from 2015 to 2017 using two outcome measures derived from infectious disease surveillance reports and to assess the completeness of these reports. Design Surveillance study. Setting Pan American Health Organization (PAHO)/WHO epidemiology reports on confirmed and suspected Zika virus infection and cases of CZS. Participants Populations of 47 countries in the South and Central Americas, Mexico and the Caribbean. Primary and secondary outcome measures The number of CZS cases per 1000 births (using 2016–2017 births as a denominator) and the number of CZS cases per 1000 births in women with Zika virus infection during pregnancy. Results By 4 January 2018, 548623 suspected and 239063 confirmed Zika virus infections had been reported to PAHO/WHO from 47 countries. In 25 countries, over 80% of infections were reported as suspected. There were 3617 confirmed CZS cases in 25 countries; 2952 (82%) had occurred in Brazil. The number of CZS cases per 1000 births varied considerably with Brazil and several Caribbean island communities (Puerto Rico, St Martin, Martinique, Guadeloupe and Grenada) having the highest CZS prevalence above 0.5 per 1000 births. Analysing the number of CZS cases per 1000 births in women infected with Zika virus during their pregnancy highlighted the inaccuracies of the data, with Venezuela likely to have had severe under-reporting of CZS. Conclusions Expressing data on CZS in relation to total births, rather than as absolute numbers, better illustrates the burden of disease, providing that under-reporting of CZS is not too severe. Data on infections in pregnant women enable potential under-reporting of CZS to be identified. Both measures are recommended for future PAHO/WHO publications. Evidence of severe under-reporting of Zika virus infections and CZS makes interpretation of the data and comparisons between countries challenging.