Zini N, Ávila MHT, Cezarotti NM, Parra MCP, Banho CA, Sacchetto L, Negri AF, Araújo E, Bittar C, Milhin BHGA, Miranda Hernandes V, Dutra KR, Trigo LA, Cecílio da Rocha L, Alves da Silva R, Celestino Dutra da Silva G, Fernanda Pereira Dos Santos T, de Carvalho Marques B, Lopes Dos Santos A, Augusto MT, Mistrão NFB, Ribeiro MR, Pinheiro TM, Maria Izabel Lopes Dos Santos T, Avilla CMS, Bernardi V, Freitas C, Gandolfi FA, Ferraz Júnior HC, Perim GC, Gomes MC, Garcia PHC, Rocha RS, Galvão TM, Fávaro EA, Scamardi SN, Rogovski KS, Peixoto RL, Benfatti L, Cruz LT, Chama PPF, Oliveira MT, Watanabe ASA, Terzian ACB, de Freitas Versiani A, Dibo MR, Chiaravalotti-Neto F, Weaver SC, Estofolete CF, Vasilakis N, and Nogueira ML
Background: Chikungunya virus (CHIKV) has spread across Brazil with varying incidence rates depending on the affected areas. Due to cocirculation of arboviruses and overlapping disease symptoms, CHIKV infection may be underdiagnosed. To understand the lack of CHIKV epidemics in São José do Rio Preto (SJdRP), São Paulo (SP), Brazil, we evaluated viral circulation by investigating anti-CHIKV IgG seroconversion in a prospective study of asymptomatic individuals and detecting anti-CHIKV IgM in individuals suspected of dengue infection, as well as CHIKV presence in Aedes mosquitoes. The opportunity to assess two different groups (symptomatic and asymptomatic) exposed at the same geographic region aimed to broaden the possibility of identifying the viral circulation, which had been previously considered absent., Methodology/principal Findings: Based on a prospective population study model and demographic characteristics (sex and age), we analyzed the anti-CHIKV IgG seroconversion rate in 341 subjects by ELISA over four years. The seroprevalence increased from 0.35% in the first year to 2.3% after 3 years of follow-up. Additionally, we investigated 497 samples from a blood panel collected from dengue-suspected individuals during the 2019 dengue outbreak in SJdRP. In total, 4.4% were positive for anti-CHIKV IgM, and 8.6% were positive for IgG. To exclude alphavirus cross-reactivity, we evaluated the presence of anti-Mayaro virus (MAYV) IgG by ELISA, and the positivity rate was 0.3% in the population study and 0.8% in the blood panel samples. In CHIKV and MAYV plaque reduction neutralization tests (PRNTs), the positivity rate for CHIKV-neutralizing antibodies in these ELISA-positive samples was 46.7%, while no MAYV-neutralizing antibodies were detected. Genomic sequencing and phylogenetic analysis revealed CHIKV genotype ECSA in São José do Rio Preto, SP. Finally, mosquitoes collected to complement human surveillance revealed CHIKV positivity of 2.76% of A. aegypti and 9.09% of A. albopictus (although it was far less abundant than A. aegypti) by RT-qPCR., Conclusions/significance: Our data suggest cryptic CHIKV circulation in SJdRP detected by continual active surveillance. These low levels, but increasing, of viral circulation highlight the possibility of CHIKV outbreaks, as there is a large naïve population. Improved knowledge of the epidemiological situation might aid in outbreaks prevention., Competing Interests: The authors have declared that no competing interests exist., (Copyright: © 2024 Zini et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)