US Faces twin health surge as new flu strain and Covid variant spread

A dual health threat is unfolding in the United States as a new influenza strain and a dominant Covid variant surge nearly simultaneously, prompting school closures in some districts and the reintroduction of masking guidelines in hospitals. The latest CDC data through December 6 show influenza activity climbing with positive flu tests up 13 percent from the prior week and hospitalizations from influenza up nearly 50 percent. When compared with the same period last year, positive tests are up about 50 percent and hospitalizations are more than double. The data also indicate “very high” flu transmission in New York City, New Jersey, Colorado and Louisiana, and health experts say the surge is largely driven by the H3N2 subclade K, a new strain to most people’s immune systems that is now circulating in more than three dozen states. Schools in several districts have closed for days due to flu-like illness, and some hospitals have reintroduced masking policies for patients, visitors and staff.

Flu activity is supported by sizable case and mortality figures. About 3 million Americans have contracted influenza A this season, which accounts for roughly three-quarters of flu cases, with about 1,200 deaths and around 30,000 people hospitalized so far. The CDC reported the first child death from influenza for the 2025-2026 season in the week ending December 11, with Colorado health officials later confirming the state’s first pediatric influenza death of the season. The agency notes that 89 percent of influenza A samples tested since September have belonged to the H3N2 subclade K, underscoring the strain’s role in the current surge. Symptoms for the so‑called super flu resemble those of earlier influenza A strains and include fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, vomiting and diarrhea. Influenza A is contagious from about one day before symptoms appear until five to seven days after becoming sick, and while most people recover within a week, lingering cough and fatigue can extend beyond two weeks. The season’s flu shot remains the primary preventive tool, though vaccine effectiveness is estimated at about 30 to 75 percent. As of late November, roughly 40 percent of American adults had received this season’s flu vaccination, a figure in line with last year’s uptake. Health officials continue to stress regular handwashing and avoiding close contact with people who are ill. The flu season in the United States typically runs from October through May.

On the Covid front, the current dominant strain is XFG, also called Stratus, which emerged in March and is now the primary driver of the illness trend in many places. The throat pain described by patients as a distinctive “razor blade” sensation has been noted alongside fever, chills, cough, shortness of breath, congestion, runny nose, body aches, vomiting and diarrhea. Unlike the flu, loss of taste or smell remains more characteristic of Covid. The CDC’s wastewater tracking shows that 67 percent of Covid samples nationwide detected through December 6 were XFG, down from 82 percent in the prior two weeks, a possible sign that a new variant may be emerging. Nationwide Covid wastewater activity is categorized as “low,” with the Northeast reporting the highest activity; nine states show increasing spread while four show declines. The latest indicators put test positivity at 3.6 percent, up from 3.1 percent the week before, while the hospitalization rate holds steady at 0.7 per 100,000 people.

The evolving picture has prompted a mixed response from health systems. Several schools have closed temporarily as clusters of flu-like illness disrupt classrooms, and some hospitals have reintroduced masking for patients, visitors and staff to curb transmission. Public health officials urge continued surveillance of both illnesses and advise vaccination and preventive practices as we head further into the winter season, which typically extends October through May in the United States. The CDC’s trend data through December 6 indicate that the spread of both influenza and Covid is likely to worsen in the coming weeks, underscoring the importance of vaccination, testing where appropriate, and basic infection-control measures during a period of overlapping respiratory illness activity.

For families and individuals weighing symptoms, doctors emphasize that distinguishing between flu and Covid can be challenging based on symptoms alone, so testing remains a key step when illness is suspected. People who are at higher risk for complications—such as older adults, young children, pregnant individuals and those with chronic conditions—should seek medical advice promptly if symptoms worsen or fail to improve. As health officials monitor the trajectory of both viruses, residents are advised to stay informed through official channels and follow local guidance on vaccination clinics, masking requirements and school policies.