Four DENV Lineages Drove Espírito Santo Dengue Surge
Key Takeaways
- In Espírito Santo, Brazil, 127,070 confirmed dengue cases were reported in 2023 and 131,170 in 2024 during back-to-back epidemic years.
- Warning signs or severe dengue were reported in 2.8% of confirmed cases in 2023 and 2% in 2024, indicating that most illness remained clinically mild.
- Dengue deaths totaled 99 in 2023 and 42 in 2024 across the consecutive epidemics.
- Co-circulating DENV-1 and DENV-2 lineages were identified, and phylogenetic reconstruction linked Espírito Santo viruses to other Brazilian and South American strains with repeated introductions inferred.
A population-based descriptive study integrated with cross-sectional genomic sampling used eSUS Health Surveillance System records for 2020-2024 and a historical monthly incidence frame extending back to 2007 in a Journal of Medical Virology study. Adults with suspected dengue virus (DENV) infection were consecutively sampled in two public health facilities in Vitória during the febrile phase shortly after symptom onset, and reverse transcription quantitative polymerase chain reaction (RT-qPCR)-positive samples meeting the cycle threshold (Ct) eligibility cutoff underwent MinION whole-genome sequencing. Overall, 340 adults were sampled, and the paper reports a small genomic set for phylogenetic reconstruction.
Dengue burden remained exceptionally high across both epidemic years, with incidence peaking between March and April and the clinical spectrum remaining predominantly mild while severe dengue stayed a very small share of notifications. Hospitalization was reported in 2.6% of confirmed cases in 2023 and 2.3% in 2024, and statewide typing suggested that DENV-1 predominated through 2020-2024 while DENV-2 accounted for a larger share in 2024; DENV-3 and DENV-4 were not detected.
Genomic sampling identified DENV-1 genotype V lineages 1V_A and 1V_E.1, DENV-2 genotype II lineage 2II_F.1.1.2, and DENV-2 genotype III lineage 2III_C.1.1 in Espírito Santo. These sequences clustered with viruses from other Brazilian regions and South America, with multiple DENV-1 lineage 1V_E.1 introductions inferred between 2019 and 2020 and at least three DENV-2 genotype II introductions inferred between 2021 and 2022.
The authors noted that the genomic component relied on convenience sampling centered in Vitória and on sequences from a limited number of municipalities, so the lineage picture was informative but not a statewide census. They also noted that public comparison genomes may miss part of the circulating diversity and that secondary surveillance records may include underreporting, overreporting, or other imprecision, especially around the COVID-19 period; lower positivity in 2023 may also reflect sampling that began after the seasonal peak. Within those limits, the authors framed the link between lineage co-circulation and the magnitude of the consecutive epidemics as a hypothesis rather than a demonstrated causal explanation.
The authors concluded that paired epidemiologic and genomic surveillance characterized both the scale of the Espírito Santo outbreaks and the diversity of DENV circulating during them.
Clinician Questions
How representative was the genomic sampling of dengue circulation across Espírito Santo?
The genomic analysis drew on convenience sampling from adults with suspected dengue seen in two public health facilities in Vitória, with heavier representation from the capital and other more populous municipalities. The authors presented the sequencing findings as a useful view of circulating viruses during the outbreaks, but not as a complete statewide census of lineage diversity.
How did the dengue virus type distribution shift during the Espírito Santo outbreaks?
Statewide typing showed that DENV-1 remained the predominant detected type across 2020-2024, but DENV-2 represented a larger share in 2024 than in earlier years. DENV-3 and DENV-4 were not detected, so the consecutive epidemics unfolded in a DENV-1 and DENV-2 co-circulation pattern rather than a full four-serotype mix.
What remains uncertain about whether co-circulating lineages drove the size of the 2023-2024 Espírito Santo epidemics?
The authors treated the link between multiple lineages and the magnitude of the consecutive Espírito Santo epidemics as a hypothesis, not a proven causal finding. Observational surveillance data, convenience genomic sampling, and incomplete public comparison sequences could underestimate introductions or miss part of the transmission network, which limits how firmly outbreak size can be attributed to lineage co-circulation alone.