High Sensitivity with Suboptimal Predictive Value and Delayed Reporting: Identifying Gaps in Congenital Zika Syndrome Surveillance at Saraburi Hospital, Thailand, 2022–2023

Zika virus is an arboviral infection primarily transmitted by Aedes mosquitoes, with severe complications in children, notably congenital Zika syndrome (CZS). This study evaluates the surveillance system of CZS based on the R506 reporting system, the nationwide reporting platform of the Department of Disease Control, at Saraburi Hospital, Thailand, during 2022–2023. We employed both quantitative and qualitative methods. A cross-sectional quantitative study was conducted through a review of hospital records and R506 surveillance data. Attributes such as sensitivity and positive predictive value (PPV) were calculated. For the qualitative study, attributes such as acceptability, simplicity, flexibility, and stability were assessed mainly through semi-structured interviews, and a framework analysis was conducted. The surveillance system demonstrated a sensitivity of 100.0% and a PPV of 44.4%. Completeness was high for demographic variables; however, timeliness was suboptimal, with 11.1% of reports submitted within a one-week window. The system was deemed useful and stable; however, challenges in interoperability between R506 and the hospital database were noted. Notably, the in-house hospital laboratory lacked the capacity to perform Zika polymerase chain reaction (PCR) tests, necessitating external processing and likely contributing to reporting delays. While the surveillance system could detect cases effectively, improvements in timeliness, coding consistency, and data integration are needed. Revising the case definition could increase the PPV. Enhancing the hospital's laboratory capacity, particularly for PCR testing, may reduce reporting time. Strengthening reporting practices and stakeholder collaboration could further improve system efficiency.