As the United States moves deeper into the winter of 2026, this year’s flu season is defined by unusually high levels of illness and strain on public health systems. Federal health officials describe the 2025–2026 flu season so far as moderately severe to severe, with activity across most of the country surpassing levels seen in recent years and, in some measures, rivaling those of major seasonal epidemics.
According to the latest cumulative estimates from the U.S. Centers for Disease Control and Prevention (CDC), influenza has sickened millions of Americans since the season began in the fall of 2025. Preliminary data indicate that there have been at least 20 million flu illnesses, 270,000 hospitalizations, and 11,000 deaths attributed to the flu during the 2025–2026 season—figures that have steadily climbed as the virus has spread across the country. These numbers are notably higher than at the same points in many recent seasons.
Despite some regional declines in recent weeks, public health surveillance shows that influenza activity has returned to elevated levels nationwide. In late January, CDC reporting indicated that after a brief decrease in cases, nation-wide activity increased again, with influenza A viruses continuing to predominate and influenza B activity rising in some regions. At times, outpatient visits for flu-like illness (fever with cough or sore throat)— which may indicate undiagnosed flu and are a supporting metric for public health monitoring and decision-making—have reached levels not seen since the late 1990s.
One key driver of this season’s intensity is a mutated strain of influenza A H3N2, known as subclade K, which has become the dominant circulating virus. H3N2 viruses are historically associated with more severe disease, particularly in older adults, and their predominance has contributed to higher hospitalization and mortality rates relative to seasons dominated by other strains.
Severity has not been limited to older age groups. Pediatric influenza deaths have occurred and, while not yet reaching the historic highs seen last season, remain a serious concern for families and health authorities. One CDC summary reported numerous pediatric fatalities, with a significant proportion of those deaths occurring in children who were not fully vaccinated against influenza. Beyond deaths and hospitalization, flu cases have forced increased healthcare use, with emergency departments and clinics reporting high volumes of patients with influenza-like symptoms throughout the winter months.
Forecasting models and public health experts anticipate that flu activity will continue through late winter and into early spring, following traditional seasonal patterns. Flu cases typically peak between December and February but can persist as late as May. The CDC and other epidemiological forecasting teams caution that the figures available now likely undercount the true burden, because many cases go undiagnosed or unreported—especially mild illnesses that do not lead to medical visits.
In response to the ongoing outbreak, public health agencies have repeatedly emphasized the importance of influenza vaccination, particularly for young children, pregnant people, older adults, and individuals with underlying health conditions. Flu vaccines have been widely available, and while vaccine effectiveness can vary based on how well the vaccine matches circulating strains, vaccination consistently reduces the risk of severe illness, hospitalization, and death. Health officials also continue to promote familiar preventive measures: frequent handwashing, staying home when ill, covering coughs and sneezes, and avoiding contact with others when symptomatic.
As the season progresses, CDC and state health departments will continue weekly surveillance and update the public on trends in illness, hospitalization, and mortality. For now, the 2026 flu season stands as a reminder that influenza remains a persistent and potentially serious threat to public health and that vaccination and infection control measures are vital tools in reducing its impact.