V. Evaluation of Cross-Immunity against Type 1 Dengue Fever in Human Subjects Convalescent from Subclinical Natural Japanese Encephalitis Virus Infection and Vaccinated with 17D Strain Yellow Fever Vaccine
In 2017, a major outbreak of Zika virus (ZIKV) infection took place in Chincha Province, Peru, where arboviral circulation had never been reported before. We conducted a cross-sectional survey (March–May 2019) in two districts of Chincha Province: Pueblo Nuevo and Chincha Baja. We included residents who were 20 to 40 years old and who had lived in these districts for at least 1 year. Serological testing combined screening with a commercial NS1 protein-based Zika IgG ELISA, and confirmation by a cytopathic effect-based virus neutralization test (VNT). Prevalence ratios (PRs) were calculated using Poisson regression with robust error variance. Four hundred participants, divided equally among districts, were enrolled. Anti-ZIKV IgG ELISA was positive for 42 participants (10.5%) and borderline for 12 (3%). Fifty-two of these 54 samples were confirmed positive by ZIKV VNT (13% of the total population). The Pueblo Nuevo district exhibited a greater ZIKV seroprevalence based on VNT results than the Chincha Baja district (23.5% versus 2.5%), with participants from the Pueblo Nuevo district being 9.4 times more likely to have a positive ZIKV VNT result. Average monthly income greater than the minimum wage and adequate water storage were found to be protective factors (PR, 0.29 and 0.24, respectively). In multivariate analysis, living in the Pueblo Nuevo district and a personal history of fever and rash were strong predictors of ZIKV positivity by VNT. The low ZIKV seroprevalence should prompt health authorities to stimulate interventions to prevent potential future outbreaks. In the Pueblo Nuevo district, the seroprevalence was greater but presumably not sufficient to ensure protective herd immunity.
Address correspondence to Rodrigo Cachay, Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru. E-mail: email@example.com
Financial support: This project, including the EuroImmun® anti-Zika Virus ELISA IgG kits and the UVE in-house ZIKV Virus Neutralization Test, was supported by the European Union’s Horizon 2020 Research and Innovation Programme under Grant Agreement N.734548. We also thank the Faculty of Medicine Alberto Hurtado, Universidad Peruana Cayetano Heredia for its partial support to cover the publication cost.
Authors’ addresses: Rodrigo Cachay, Alvaro Schwalb, J. Gonzalo Acevedo-Rodriguez, Humberto Guerra, and Eduardo Gotuzzo, Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru, E-mails: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, and firstname.lastname@example.org. Xiomara Merino and Michael Talledo, Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru, and Unidad de Epidemiología Molecular, Instituto de Medicina Tropical Alexander von Humboldt, Universidad Peruana Cayetano Heredia, Lima, Peru, E-mails: email@example.com and firstname.lastname@example.org. Luis Suarez-Ognio, Facultad de Medicina, Universidad Peruana Ciencias Aplicadas, Lima, Peru, E-mail: email@example.com. Laura Pezzi and Xavier de Lamballerie, Unité des Virus Émergents, Aix-Marseille University, Marseille, France, E-mails: firstname.lastname@example.org and email@example.com. Thomas Jaenisch, Heidelberg Institute of Global Health, Heidelberg University Hospital, Heidelberg, Germany, and Colorado School of Public Health, University of Colorado, Anschutz Medical Campus, Aurora, CO, E-mail: firstname.lastname@example.org.