Multiple diseases, including pertussis (whooping cough), influenza, respiratory syncytial virus (RSV), and COVID-19, are contributing to increased respiratory illness activity across the United States and globally as the 2025–26 respiratory season unfolds.

Arkansas sees spike in whooping cough cases

More than 500 pertussis cases were reported in Arkansas this year, marking the highest annual total since the state began collecting data on pertussis 15 years ago, according to a state health department press release. Cases aren’t concentrated in a specific region—more than 50 counties in Arkansas have logged at least one case.

Children and adolescents make up the majority of cases in the state, and at least 50 hospitalizations have occurred. Infants younger than 1 year account for over 60% of these hospitalizations, and one pertussis-related death was reported in Arkansas this year. 

Vaccination remains the most effective prevention strategy, say public health officials, and they encourage prompt antibiotic treatment and post-exposure prophylaxis when appropriate. 

Flu activity is high and continues to rise, driven by subclade K

According to the most recent Influenza Surveillance Report (the week ending December 20) from the Centers for Disease Control and Prevention (CDC), seasonal influenza activity remains elevated and is increasing across the United States. 

Influenza A(H3N2) viruses predominate, with a large portion of circulating strains (89.5%) belonging to subclade K. A relatively new strain of influenza A, subclade K has fueled an earlier- than-usual start to the flu season and given rise to higher case counts across parts of the country and globe. 

The CDC estimates at least 7.5 million illnesses, 81,000 hospitalizations, and 3,100 deaths from the flu so far this season. Eight influenza-related pediatric deaths have been reported to the CDC, which continues to recommend annual influenza vaccination for all persons aged 6 months and older.

COVID cases rising in 39 states; severe disease in Europe

CDC’s Center for Forecasting and Outbreak Analytics estimates that COVID-19 infections are growing or likely growing in 39 states, with no states showing clear declines in transmission. Influenza cases are growing in 29 states, and RSV infections are growing or likely growing in 41 states. (Holiday reporting delays may influence these trends.).

COVID continues to cause hospitalizations and deaths throughout Europe, particularly among adults older than 60 and persons with chronic conditions, according to the World Health Organization (WHO). Vaccination remains effective at reducing the risk of severe disease and hospitalization, notes the WHO, yet uptake among high-risk groups remains low in some regions.