Epidemiological investigation of a confirmed case of West Nile virus in Campo Novo do Parecis, Mato Grosso, Brazil, 2025-2026.

OBJECTIVE

To describe the epidemiological investigation following laboratory confirmation of West Nile virus in an infant residing in Mato Grosso, Brazil.

METHODS

Descriptive study conducted between February 11 and 13, 2026, following notification and diagnostic confirmation by molecular biology. Passive and active surveillance were implemented.

RESULTS

The index case had symptom onset on December 18, 2025, confirmed by molecular biology in a cerebrospinal fluid sample collected on December 20, 2025. In the active investigation, 112 residents were interviewed, identifying 29 symptomatic individuals (25.9%), of whom eight reported neurological manifestations. Environmental conditions favorable to vector proliferation were observed.

CONCLUSION

The findings suggest possible viral circulation and reinforce the need to intensify integrated human-animal-environmental surveillance, with expanded laboratory and entomological investigation in our territory.