# Characterization of the most austral autochthonous dengue outbreak reported in the world (city of Bahía Blanca, Argentina, January–June 2024). A cross-sectional study

## TL;DR

This study reports the southernmost dengue outbreak in the world, in Bahía Blanca, Argentina, highlighting the disease's geographic expansion.

## Contribution

The paper documents the first autochthonous dengue outbreak at such a low latitude, expanding known risk areas.

## Key findings

- A total of 94 dengue cases were confirmed, with 63 classified as autochthonous.
- DENV1 and DENV2 serotypes were detected in both autochthonous and imported cases.
- The outbreak peaked in the thirteenth epidemiological week, with the first case in the second week.

## Abstract

Dengue is a vector-borne viral disease that is expanding its boundaries, causing outbreaks and autochthonous viral circulation in places where it had not previously been recorded. The aim is to describe epidemiologically the first outbreak of dengue in the southernmost latitude of the planet ever recorded.

In Bahía Blanca (Buenos Aires, Argentina), dengue virus circulation was reported between January 1, 2024, and June 10, 2024. Cases were detected and reported to the Health Secretariat of the Municipality of Bahía Blanca, Province of Buenos Aires, Argentina. The cases were clinically diagnosed and tested positive for dengue virus (DENV) nonstructural protein 1 (NS1), RT-PCR, and/or IgM. Cases were classified as autochthonous when patients did not report traveling to areas with dengue circulation during the 15 days prior to the onset of symptoms. All serological and molecular analyses were performed at the Municipal Hospital. This study was conducted using clinical samples and data obtained during the outbreak, and all personal identifiers were excluded.

A total of 94 positive cases were reported out of 470 suspected cases. Of the total confirmed cases, 63 were classified as autochthonous and 28 as imported. Serotypes DENV1 and DENV2 were detected in both cases. The first autochthonous case was identified in the second epidemiological week, and the peak of the epidemic curve occurred in the thirteenth epidemiological week. Twenty-seven imported cases came from Argentine locations with autochthonous viral circulation, and one came from Paraguay.

This study provides clear evidence of the expansion of dengue fever to latitudes that were not included in previously published risk maps for Argentina. Reporting on the expansion of dengue fever to new areas should alert decision-makers to adopt public health policies aimed at reducing the burden of the disease.

LSB, GGB, RS were partially funded by the call 18/2023 by the 10.13039/501100003593National Council for Scientific and Technological Development (CNPq) and the Department of Science and Technology of Secretariat of Science, Technology, Innovation and Health Complex of 10.13039/501100006506Ministry of Health of Brazil (DECIT/SECTICS/MS). LSB also acknowledges research grants from 10.13039/501100004586FAPERJ (E-26/201.277/2021) and 10.13039/501100003593CNPq (310530/2021-0).