United States: In February 2025, influenza cases escalated to their highest levels in over 15 years, surpassing COVID-19 infections and hospitalizations for the first time since the onset of the pandemic. The Centers for Disease Control and Prevention (CDC) has categorized this flu season as exhibiting “high” severity nationwide. 

To gain a deeper understanding of the situation, The Conversation consulted epidemiologist Annette Regan to shed light on the factors driving this surge and to explore potential measures for mitigation. 

How Do This Year’s Flu Cases and Hospitalizations Compare to Previous Years? 

From late January through February 2025, hospitalizations due to influenza have reached unprecedented levels, exceeding any peak recorded since before 2009. 

The predominant culprits behind this wave appear to be influenza A strains, with a division between influenza A/H3N2 and influenza A/H1N1. These subtypes, while distinct, both possess the capacity to trigger severe illness. 

Historically, flu seasons dominated by influenza A/H3N2 have been associated with heightened severity. However, infections caused by influenza A/H1N1 can also result in severe complications, according to The Conversation. 

Another distinguishing feature of this season is its delayed peak. Unlike the previous three flu seasons, which reached their zenith in December, the current wave has surged later in the winter months. 

Tragically, this flu season has also claimed a significant number of lives. Since January 1, 2025, over 4,000 individuals, including 68 children, have succumbed to influenza. Although these fatalities do not set a new record, they underscore the serious health risks posed by the flu—even for children. 

Why Are Flu Cases So Elevated This Year? 

Several elements contribute to a particularly severe flu season, including waning community immunity due to declining vaccination rates, the intrinsic properties of circulating viral strains, vaccine efficacy, and increased human interactions through travel, workplaces, and educational institutions. 

Unfortunately, flu immunization rates have plummeted since the COVID-19 pandemic. By the conclusion of the 2023-24 flu season, 9.2 million fewer vaccine doses had been administered in pharmacies and healthcare facilities compared to pre-pandemic averages. 

Additionally, since 2022, private manufacturers have distributed fewer flu vaccine doses. Historically, adult flu vaccination rates have fluctuated between 30% and 60%, falling short of the recommended 70%. Prior to the pandemic, flu vaccine uptake had been steadily increasing by 1% to 2% annually. 

Following the pandemic, flu vaccination rates began to decline, particularly among high-risk populations. Pediatric vaccination rates have dropped from 59% in the 2019-20 season to 46% in 2024-25. Among adults aged 65 and older—who face the highest risk of hospitalization and mortality—vaccination rates have declined from 52% in 2019-20 to 43% in 2024-25, as per The Conversation. 

Lower immunization rates translate to a larger proportion of the population lacking vaccine-derived protection. Research consistently demonstrates that flu vaccination reduces the likelihood of hospitalization. Even when vaccinated individuals contract influenza, their risk of experiencing severe illness diminishes significantly. Consequently, reduced vaccine uptake is a key contributor to this season’s heightened flu burden. 

However, declining vaccination rates alone do not fully explain the alarming rise in cases. In previous severe seasons, genetic mutations within circulating viral strains have enhanced their transmissibility and virulence. 

The efficacy of the annual flu vaccine fluctuates based on how well it aligns with circulating viral strains. Historically, vaccine effectiveness has ranged from 19% to 60%. For the 2023-24 flu season, the vaccine demonstrated 42% efficacy. 

Early data from the 2024-25 flu season suggests that the vaccine is between 41% and 55% effective in preventing flu-related hospitalizations among adults and 63% to 78% effective in children. 

How Do Flu Symptoms Differ from COVID-19 and Other Illnesses? 

It is common for individuals to mistakenly attribute common colds to influenza. However, true influenza is solely caused by the influenza virus and tends to be far more severe than the common cold, often accompanied by fever. 

Many respiratory illnesses—including flu, COVID-19, and other viral infections—share overlapping symptoms that can range from mild congestion to severe pneumonia and respiratory distress. Hallmark flu symptoms include fever, cough, and profound fatigue, often accompanied by shortness of breath, sore throat, nasal congestion, muscle aches, and headaches, according to the reports by The Conversation. 

Some symptoms, such as altered or lost sense of taste and smell, are more characteristic of COVID-19. For both flu and COVID-19, symptoms typically manifest between one to four days post-infection, though COVID-19 symptoms tend to persist longer. 

The only definitive method to determine the cause of an illness is testing. Rapid tests—some of which now screen for both flu and COVID-19—can provide quick results, while laboratory-based nasal swabs offer a more comprehensive analysis. Prescription antiviral medications are available for both flu and COVID-19, but they are most effective when taken shortly after symptom onset. 

Certain populations, including immunocompromised individuals, diabetics, and those with chronic heart or lung conditions, are at heightened risk for severe complications from flu and COVID-19. In such cases, seeking timely medical care is essential. Telehealth consultations are also an option, reducing the strain on emergency rooms and urgent care centers when infection rates are high. 

What Can People Do to Reduce Their Risk of Flu? 

There are several proactive measures individuals can take to minimize their risk of contracting and spreading influenza. Given that flu season is still ongoing, receiving a flu vaccine remains a viable and beneficial option. Even in seasons where vaccine efficacy is lower, it still offers substantial protection compared to remaining unvaccinated. 

Practicing good hygiene, such as regular handwashing and disinfecting high-touch surfaces, can help mitigate viral transmission. Avoiding close contact with infected individuals and wearing masks in healthcare settings can also provide an additional layer of protection. 

Maintaining overall health through regular exercise, a balanced diet, and sufficient sleep strengthens the immune system, thereby reducing susceptibility to infections. 

Those diagnosed with flu or experiencing flu-like symptoms should avoid crowded environments and minimize contact with others. Simple precautions—such as covering coughs and sneezes—can significantly reduce viral spread, as per The Conversation. 

Final Thoughts 

The 2024-25 flu season has demonstrated an alarming increase in both cases and hospitalizations, underscoring the importance of flu prevention measures. While vaccination rates have declined, receiving a flu shot remains one of the most effective tools in preventing severe illness. Coupled with diligent hygiene practices and health-conscious lifestyle choices, individuals can take proactive steps to safeguard themselves and their communities from the flu’s impact.