Seasonal Influenza Viruses Are Circulating in the Americas

The Pan American Health Organization/World Health Organization (PAHO/WHO) issued an alert today regarding the possibility of earlier or more intense respiratory virus activity during the 2025-26 season compared to previous years.

As of January 9, 2026, PAHO/WHO recommends that Member States remain vigilant to adjust their health service preparedness and organizational plans in anticipation of possible concurrent outbreaks of seasonal influenza and respiratory syncytial virus.

Globally, influenza activity has increased since late 2025.

Some countries are reporting an early onset of the influenza season, with influenza A(H3N2) viruses being the most predominant, while A(H1N1)pdm09 is the primary strain in the Andean subregion.

In the Americas Region, the influenza positivity rate remains above 10% in the Northern Hemisphere. The intensity of activity varies, with positivity levels approaching 20% in the Caribbean and Central America.

Countries such as Barbados, Canada, Ecuador, Guatemala, Nicaragua, Panama, Paraguay, and the United States are reporting high levels of influenza circulation.

In contrast, RSV circulation remains low.

Regarding this season's flu shots' effectiveness, many are questioning whether the updated vaccines provide adequate protection against the disease.

A study from the University of Pennsylvania released on January 6, 2026, found that while subclade K viruses are antigenically advanced compared to the vaccine strain, the 2025-2026 vaccine still elicited robust antibody responses in many participants.

Furthermore, the PAHO/WHO recommends flu shots for international travelers before visiting outbreak areas.

Access to influenza vaccines remains robust in the USA, with most clinics and pharmacies offering services as of January 10, 2026.