Mem Inst Oswaldo Cruz, Rio de Janeiro, VOLUME 121 | 2026
Research Articles

Entomo-virological investigation during the epizootic outbreak of sylvatic yellow fever in Rio Grande do Sul, Brazil, between 2021 and 2022

Nícolas Felipe Drumm Müller1,2,+, Marcelo de Moura Lima2, Edmilson dos Santos2, Aline Alves Scarpellini Campos2, Thomas Rosa Menegazzi2, Alanis Silva Melgarejo1, Bruna Paredes-Galarza1, Lina Violet-Lozano1, Martha Trindade Oliveira1, Cirilo Henrique Oliveira3, Paulo Michel Roehe1,†, Fabrício Souza Campos1, Filipe Vieira Santos de Abreu3,4, Jáder da Cruz Cardoso2, Ana Cláudia Franco1,+

1Universidade Federal do Rio Grande do Sul, Instituto de Ciências Básicas da Saúde, Laboratório de Virologia, Porto Alegre, RS, Brasil
2Secretaria Estadual de Saúde do Rio Grande do Sul, Centro Estadual de Vigilância em Saúde, Porto Alegre, RS, Brasil
3Instituto Federal do Norte de Minas Gerais, Laboratório de Comportamento de Insetos, Salinas, MG, Brasil
4Fundação Oswaldo Cruz-Fiocruz, Instituto Oswaldo Cruz, Laboratório de Mosquitos Transmissores de Hematozoários, Rio de Janeiro, RJ, Brasil

DOI: 10.1590/0074-02760250169
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ABSTRACT

BACKGROUND Yellow fever virus (YFV) re-emerged among non-human primates (NHPs) in Rio Grande do Sul in early 2021, more than a decade after its last detection in the state. The spread of the virus was accompanied by increased mortality among NHPs.
OBJECTIVES To conduct entomological surveillance and molecular detection of YFV and other Orthoflavivirus species in mosquito samples collected from affected and potentially receptive areas.
METHODS Mosquitoes were collected during epizootics using human landing catches, BG-Pro traps, and ovitraps. Virus detection was performed using reverse transcription real-time polymerase chain reaction (RT-qPCR) assays targeting YFV and pan-Orthoflavivirus sequences.
FINDINGS A total of 1,210 mosquitoes, representing 26 taxa, were collected across 17 municipalities. Psorophora ferox was the most abundant species, followed by Culex (Culex) spp., accounting for 27% and 12% of the specimens, respectively. Haemagogus leucocelaenus, the primary YFV vector in the region, was also among the most frequently captured species, representing 7%. In total, 203 mosquito pools were assembled by species, location, and date of collection. RT-qPCR analysis did not detect YFV or other Orthoflavivirus RNA in any of the samples.
MAIN CONCLUSIONS Although mosquitoes were collected during a period of active YFV circulation, the absence of virus detection suggests that arboviral circulation in vector populations may occur at low frequencies, even during outbreaks.

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Financial support: The project was supported by grants from CNPq/Departamento de Ciência e Tecnologia/Secretaria de Ciência, Tecnologia e Insumos Estratégicos/Brazilian Ministry of Health (CNPq/Decit/SCTIE/MS) (grant number 443215/2019-7 to ACF, PMR and FSC).
† In memoriam
+ Corresponding authors: nicolas-muller@saude.rs.gov.br | ORCID https://orcid.org/0000-0002-6322-252X / anafranco.ufrgs@gmail.com | ORCID https://orcid.org/0000-0001-7747-5125
Received 08 July 2025
Accepted 30 October 2025

HOW TO CITE
Müller NFD, Lima MM, dos Santos E, Campos AAS, Menegazzi TR, Melgarejo AS, et al. Entomo-virological investigation during the epizootic outbreak of sylvatic yellow fever in Rio Grande do Sul, Brazil, between 2021 and 2022. Mem Inst Oswaldo Cruz. 2025; 120: e250169.

HANDLING EDITOR
Ademir de Jesus Martins Jr | ORCID https://orcid.org/0000-0001-5739-1215

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