Dengue: Following an unexpected rise in cases, prevention efforts are being intensified amid the threat of El Niño

Argentina's Ministry of Health is urgently stepping up dengue prevention efforts, prompted by an unexpected surge in cases and forecasts indicating a prolonged presence of the Aedes aegypti mosquito. This proactive stance is driven by a confluence of factors, including a mid-month uptick in suspected cases, a trend contrary to seasonal expectations, and climate predictions linked to the El Niño phenomenon.

While the 2025-2026 season was initially assessed as low-risk for dengue, the situation has evolved. Neighboring countries have experienced chikungunya outbreaks, and the Aedes aegypti mosquito, the vector for both diseases, is now expected to thrive year-round due to warmer temperatures. This persistent presence necessitates continuous preventive actions.

The epidemiological season for mosquito-borne diseases runs from July to July. In the closing season (2025-2026), Argentina has recorded 2,819 confirmed and probable chikungunya cases out of 12,928 notifications over 11 months. Dengue cases remain significantly lower, with only 69 confirmed cases from over 27,363 suspected notifications. Notably, 55% of infections were autochthonous, meaning they were contracted within the individual's usual environment.

Despite a general trend of low dengue circulation, a notable increase in suspected cases was observed mid-last month. Approximately 206 cases required diagnosis confirmation, with an additional 335 probable cases pending. These were primarily reported in Buenos Aires, Córdoba, the City of Buenos Aires, Tucumán, and Santa Fe. Authorities are also considering the possibility of delayed data entry, a common issue in national health statistics, while acknowledging the persistent warm temperatures conducive to the mosquito's life cycle.

In response, the Ministry of Health has emphasized the critical need to enhance the quality of epidemiological surveillance. This includes ensuring the collection of second samples and completing diagnostic studies for probable cases to accurately confirm or rule out dengue. The ministry stresses that abandoned tires holding accumulated water can become breeding grounds for mosquitoes, highlighting the importance of community-level prevention efforts.