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Instances of influenza have been remarkably elevated in the United States this period. Authorities clarify the reasons.(Image credit: Tunyada Kongkapan via Getty Images)ShareShare by:
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If you suspect that many individuals around you have contracted the flu, it is indeed the case.
As of January 9, the U.S. Centers for Disease Control and Prevention (CDC) approximates that a minimum of 15 million individuals have been afflicted with the flu this period. Within that group, 180,000 needed hospitalization, and thus far, 7,400 individuals have perished from the flu, encompassing 17 children.
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At Phoenix Children’s Hospital, high rates of influenza have been noted since the center of December 2025, affirmed pediatric infectious disease expert Dr. Monica Abdelnour.
“Even though current estimations from the CDC indicate a moderately impactful flu period, the recorded rates are comparable to, and marginally beyond those detected throughout 2024-2025, which was considered a year of great consequence,” she informed Live Science via electronic correspondence. “There persists the possibility that this particular flu period may ultimately warrant categorization as having extensive implications.”
Even though the CDC noted a slight lessening in lab-confirmed flu reports during the initial week of 2026, in relation to the closing week of 2025, Madad shared with Live Science that declaring that the summit has passed is premature. In the U.S., influenza activity typically peaks in the interval spanning December and February. The CDC further mentioned that the modest reduction in substantiated occurrences might link to anticipated declensions in medical consultations and laboratory tests during the vacation phase, rather than a tangible reduction in influenza propagation.
What is subclade K?
Subclade K has featured extensively in discussions related to this season’s influenza.
Understanding its essence entails recognizing that influenza viruses undergo continuous change, accumulating minor genetic shifts as they circulate. Madad clarified that scientists track the progress of these viruses by using a system akin to a lineage chart.
The principal sectors of this chart are designated as “types.” This involves influenza A and B, which are expansive clusters of influenza viruses. These primary segments subsequently diverge into smaller branches referred to as subtypes, exemplified by A(H3N2) or the B/Victoria lineage.
The terms H and N, utilized to distinguish influenza A subtypes, denote two surface proteins of the virus: hemagglutinin (H) and neuraminidase (N). An extensive array of versions is possible for each protein — numbering 18 and 11, individually — thus generating a multitude of influenza viruses, with only a select few consistently infecting individuals.
Proceeding further within a branch, scientists recognize “clades,” designating communities of viruses derived from a mutual predecessor with akin genetic features. A subclade signifies a still more restricted group inside a clade — a more contemporary “offshoot” of the chart — with shared novel transformations.
This influenza season, the CDC communicated that the majority of influenza occurrences are attributable to the influenza subtype A(H3N2). From over 430 influenza A(H3N2) virus specimens amassed since the final segment of September 2025, more than 91% were recognized to belong to a carefully linked community categorized as subclade K.
Is subclade K a “super flu”?
The response is negative.
Madad explained that subclade K showcases distinctive mutations in sections of the virus typically acknowledged by immune systems. As a consequence, the protection conferred by prior influenza contagions or inoculations is reduced relative to the anticipated response had the subclade presented a more recognized aspect. This favors enhanced viral transmission, increasing the instance count and resultant hospital admissions.
Nonetheless, Madad stipulated that this doesn’t inherently imply that subclade K is more hazardous or engenders more intense illness relative to other current influenza viruses. She also observed that current epidemiologic data don’t reflect that subclade K is associated with a graver illness than the other recurrent influenza strains in propagation.
“This year’s influenza indications are akin to those observed throughout prior periods,” Abdelnour appended.
Typical influenza experiences encompass pyrexia or chills, coughing, nasal congestion, muscular and/or bodily pains, cephalgia, and weakness. Severe influenza infections can engender sequelae such as septicemia and pneumonia. Adults 65 and over; young children, specifically those under 2; pregnant individuals; and individuals grappling with persistent ailments like asthma, diabetes, or cardiovascular conditions, are at increased jeopardy of serious influenza consequences.
Is this year’s flu vaccine effective, and is it too late to get it?
Madad stated that the influenza immunization “might exhibit a less perfect convergence with subclade K” than optimal, although she emphasized the indispensable function of inoculation in averting severe illness. Abdelnour specified that the yearly influenza inoculation reduces the chance of critical sequelae, like septicemia, pneumonia, and substantial neurologic symptoms, such as convulsions.
Abdelnour added that evidence from the Southern Hemisphere, which undergoes influenza season ahead of the Northern Hemisphere, implies the recent influenza inoculation performs at par with past vaccinations in diminishing the chances of influenza-induced hospital stays. As indicated by a CDC study issued in September 2025, the influenza inoculation diminished influenza-related healthcare visits and hospital stays by 50% in the Southern Hemisphere across the latest influenza season.
“This falls within the common range, and we project experiencing comparable tiers of protection in the United States,” Abdelnour declared.
Unfortunately, there has been a drop in influenza vaccinations this year, primarily among children, according to Madad. “Roughly 42% of U.S. children have secured influenza inoculations to date this season, reflecting a decrease from about 53% at a comparable phase in 2019–2020.” As of January 3, around 44.1% of adults self-reported having received an influenza vaccination.
Madad alerted that subpar inoculation percentages can entail tangible repercussions. During the influenza period of 2024-2025, 280 children across the U.S. succumbed to influenza-linked ailments, wherein about 9 in 10 had not secured inoculation against the virus. Madad, who identifies as a mother of four, indicated that each of her offspring are inoculated annually.
Despite influenza season initiating during autumn, Abdelnour reinforced that “initiating influenza vaccination is not precluded.” “Considering the current intensification of cases, prompt inoculation is keenly encouraged to safeguard oneself and those in close proximity.”
Madad echoed this stance, imploring any yet-to-be inoculated persons this season, specifically adults ages 65 and older, pregnant individuals, those displaying compromised immune function, and individuals coping with long-standing health concerns, to initiate vaccination as they shoulder a heightened likelihood of acute cases.
How else can you protect yourself from flu?
Inoculation signifies only one facet of protection. Madad accentuated the necessity of donning a conforming mask within crowded indoor locations, alongside amplifying the ventilation during enclosed gatherings. Moreover, persons ought to isolate at home while ailing to prevent any contagion propagation. These precautions curb the propagation not solely of influenza, but likewise of supplementary respiratory viruses like COVID-19 and RSV (respiratory syncytial virus).
Abdelnour further referenced the relevance of preserving exemplary hand sanitization. “Special consideration needs to be rendered to scholastic environments such as kindergartens and daycare facilities,” she posited. “This encompasses encouraging children to be inoculated, fostering rigorous handwashing with suds and water for a duration surpassing 20 seconds, and retaining ailing children at their domicile to impede infection contagion to other individuals.”
Are there treatments for flu?
For those who become infected, antivirals like Tamiflu provide relief. These prescribed pharmaceuticals diminish the severity of indicia and shorten the duration of illness, chiefly upon consumption within one or two days following the inception of indicia. Evidence suggests particular benefit to individuals admitted to hospitals because of influenza.
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The CDC advocates instantaneous intervention for individuals suspected of manifesting influenza indicia who concurrently shoulder escalated vulnerability to grave influenza sequelae, as exemplified by expectant women and individuals enduring chronic health anomalies, spanning asthma, pulmonary disorders, diabetes, or heart conditions.
Madad articulated that influenza antivirals are “underused” and prompts individuals at increased peril of critical influenza or who act as caretakers of susceptible persons to consult with their physicians pertaining to antivirals soon after suspecting a contagion. Positively, up-to-date findings illustrate subclade K remains amenable to prevalent antiviral pharmaceuticals administered by clinicians against influenza, she affirmed.
Disclaimer
This article is designated solely for informational objectives and refrains from constituting medical counsel.
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Clarissa BrincatLive Science Contributor
Clarissa Brincat functions as a freelance scribe focused on wellness and medical explorations. Following the achievement of an MSc in chemical sciences, she inferred that her predilection inclined more toward the articulation of science rather than its conduction. She sharpened editorial aptitudes concerning scientific documents through a brief term as a chemistry proofreader, followed by a medical scribe designation at a healthcare establishment. Penning content for physicians and specialists carries value, but Clarissa aspired to interface with an ampler demographic, inevitably conducing her toward freelance wellness and science scripture. Her oeuvre is featured in Medscape, HealthCentral, and Medical News Today.
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