Health officials in the United States have reported a significant increase in cases of flu, norovirus, and COVID-19 as the holiday travel season approaches. The current flu outbreak is predominantly linked to the newly identified H3N2 subclade K strain, raising concerns about potential outbreaks during family gatherings.
The Centers for Disease Control and Prevention (CDC) indicates that the H3N2 subclade K strain has become the dominant influenza strain in the U.S., accounting for approximately 89 percent of H3N2 infections since late September. This strain emerged after the formulation of the 2025-26 flu vaccine, leading to fears of a reduced immune response among vaccinated individuals. Symptoms associated with this year’s flu remain familiar, including fever, chills, severe fatigue, cough, and body aches. Nonetheless, the vaccine mismatch could result in a higher number of infections and severe cases.
According to CDC data published on December 15, 4.6 million flu cases, 49,000 hospitalizations, and 1,900 deaths have been documented this season. The week ending December 13 saw a substantial rise in cases, with the percentage of positive tests increasing from 8.1 percent to 14.3 percent. School districts nationwide have reported closures due to rising flu cases among students and staff.
Norovirus and Its Rapid Spread
Norovirus, often referred to as the “winter vomiting disease,” is also experiencing a notable surge across the country. Wastewater data from WastewaterSCAN reveals a 69 percent increase in viral concentrations since October, prompting the organization to classify the national risk as “high.” The Northeast and Midwest regions have been particularly affected, with localized outbreaks reported in states such as Illinois and Texas.
The CDC has noted that norovirus positivity rates have doubled, reaching nearly 14 percent in clinical tests conducted by mid-November, compared to three months prior. This increase has led to heightened emergency room visits and school closures.
Children are experiencing significant impacts from both flu and norovirus outbreaks. In Marin County, California, approximately one-third of students were reported absent due to flu-like symptoms, while attendance dipped in New York City schools amid hundreds of pediatric flu cases. Schools across the country are taking proactive measures, including deep cleaning and disinfecting facilities, in preparation for the winter break.
Concerns Ahead of Holiday Travel
The upcoming holiday travel period is expected to be one of the busiest on record, with AAA estimating that 122 million Americans will travel between December 20 and January 1. Crowded airports and family gatherings create ideal conditions for the spread of respiratory viruses. Health officials are urging the public to stay home if symptomatic, practice thorough handwashing, and receive vaccinations against influenza and COVID-19. Despite some vaccine mismatches, officials emphasize that vaccinations can significantly reduce the likelihood of severe illness, hospitalization, and death.
Dr. Farrell Tobolowsky, medical director for communicable diseases at the San Francisco Department of Public Health, emphasized the importance of seeking medical attention if symptomatic, particularly for those at higher risk for severe illness. Virologist Andy Pekosz from Johns Hopkins Bloomberg School of Public Health noted, “Symptom-wise, nothing that we know that’s different about this virus outside of the fact that it’s just going to be able to infect more people and therefore we’ll see more cases.”
Dr. Robert Hopkins Jr. from the National Foundation for Infectious Diseases echoed the concerns surrounding the new H3N2 strain, stating, “Knowing that there’s a new mutated strain out there and H3N2 generally causes more severe disease is concerning.”
As the holiday season unfolds, the CDC, along with state and local health agencies, will closely monitor viral trends, anticipating further spikes in cases as Americans return home. Public health officials continue to advocate for preventive measures to protect communities during this critical period.
