Zika Syndrome: Assessing the fatality rate since the 2015 Zika outbreak

Abstract

Background: Many studies have demonstrated a causal link between Zika virus (ZIKV) infection, microcephaly (MCP) and other congenital abnormalities (CA). We aimed to determine the perinatal case fatality rate in cases of Congenital Zika Syndrome (CZS) in the Rio Grande do Norte State (RN), a Brazilian Northeast State highly impacted by the Zika outbreak. Methods and materials: A cross-sectional study was conducted using data obtained through the State Health Department (SHD) for cases of MCP and CA in RN from April 2015 to December 31, 2017. Definition of perinatal period: commences at 22 completed weeks (154 days) of gestation and ends seven completed days after birth. Perinatal case fatality rate is defined as the number of deaths as a fraction of the number of sick persons with a specific disease (×100). Results: During the study period, there were 519 cases of MCP and others CA notified in RN, of which 150 were confirmed and 126 remain under investigation. The remaining 243 cases have been ruled out by presenting normal exams or due to presenting microcephaly by non-infectious causes. Of the total confirmed cases, 30.0% (45/150) died after birth or during pregnancy. 64.4% (29/45) of confirmed deaths had ZIKV infection during pregnancy and 4.4% (02/45) had a positive TORCH blood test. The deaths related to Zika were confirmed using either clinical/epidemiological/radiological (the presence of typical and indicative alterations of congenital ZIKV infection) or clinical/epidemiological/serological (RT-PCR and/or IgM/IgG antibodies against ZIKV). Eleven cases remain under investigation and five were ruled out. Conclusion: This study highlights a high rate of perinatal lethality (64.4%) in cases of CZS. Despite the growing number of CZS cases, the real incidence and prevalence might be higher due to the underreporting and lack of resources for confirmatory diagnostic tests (laboratory and imaging). Due to the high rate of lethality, our findings predict an increase in the infant mortality rate in areas endemic for arboviruses. Because the severe neurological complications caused by CZS, it is likely to pose a substantial burden on public spending on healthcare. This study may be used to better describe the CZS, its prognosis and natural history.