Flu cases are on the rise in California, and health officials are sounding the alarm over a powerful new virus strain that is leading to an increase in flu-related illnesses and hospitalizations across the state. This warning is being echoed by public health experts nationwide, highlighting a growing concern.
The newly identified strain, known as the H3N2 subclade K, is already causing significant disruptions globally, and California's hospitals and clinics are feeling its impact, as noted by the state’s Department of Public Health in a recent announcement. While specific figures for California have not been disclosed, the department has categorized the flu activity in the state as being at an "elevated" level.
Dr. Elizabeth Hudson, who serves as the regional physician chief of infectious diseases for Kaiser Permanente, explained that flu cases began to climb noticeably around mid-December and continue to rise. "We hope to see some stabilization in the coming weeks, but there may be delays in data reporting due to the recent holiday period," she stated.
Most individuals with flu symptoms are being treated without needing hospitalization, but the elderly and those with pre-existing health conditions are more likely to require admission to the hospital.
Recent statistics from the public health agency indicate that Central California and the Bay Area are experiencing a high positivity rate for flu cases, while areas like Sacramento and Southern California report moderate rates. In contrast, Northern California, which comprises more rural locations, currently shows low flu activity according to the agency’s website.
In Los Angeles County, the local health department recently reported that from the end of last year into the beginning of 2026, there were 162 hospitalizations related to flu, including 18 patients who required intensive care.
This flu season has already turned out to be one of the worst in the United States in over three decades. The Centers for Disease Control and Prevention (CDC) estimates that since late fall, there have been at least 15 million infections, resulting in approximately 180,000 hospitalizations and 7,400 deaths. Alarmingly, at least two of the fatalities were children, as confirmed by Yvonne Maldonado, a professor of global health and infectious disease at Stanford Medicine. The state’s Department of Public Health also verified that these pediatric deaths occurred in California.
Experts had warned last year that this flu season could pose significant risks to high-risk groups, particularly children, due to declining vaccination rates alongside the emergence of a "mutated" strain of the virus. Dr. Peter Chin-Hong, an infectious diseases expert at UC San Francisco, pointed out that the combination of these factors could lead to a particularly harsh flu season.
Reflecting on previous seasons, Dr. Neha Nanda, who is the medical director of antimicrobial stewardship with Keck Medicine of USC, noted that while last year's flu season was one of the most severe, the current year may surpass it in terms of impact. She has observed an early increase in positive influenza cases compared to prior years, although it has not yet reached the severity seen last year.
Dr. Sam Torbati, co-chair and medical director of Cedars-Sinai Medical Center’s emergency department, reported a surge of patients presenting with flu-related ailments around the second week of December, indicating a troubling trend in hospital admissions throughout the county. He remarked, "I don't recall seeing this many patients becoming this ill so early in the season. It is still early to predict how much worse this could get."
Health experts suspect that the H3N2 subclade K strain has mutated in a way that increases its ability to evade immunity provided by the existing vaccines. This strain emerged later in the summer, after health officials had already finalized the vaccine formula.
Despite concerns about the effectiveness of the flu vaccine against this strain, Dr. Erica Pan, the state public health officer, reassured that current seasonal flu vaccines can still significantly reduce the risk of severe illness and hospitalization from the circulating viruses.
Even if the flu shot doesn’t entirely prevent the illness, it is still beneficial. Dr. Michelle Barron, the senior medical director of infection prevention and control at UCHealth, explained that receiving the vaccine diminishes the likelihood of developing a severe case, helps avoid hospitalization, and shortens recovery time.
Health authorities are strongly advising the public, particularly individuals at higher risk for serious flu complications—such as young children and the elderly—to get vaccinated or seek immediate antiviral treatment options, such as Tamiflu.
The flu can manifest with serious symptoms including fatigue, fever, cough, and body aches, making individuals feel as though they’ve been "hit by a Mack truck," remarked Dr. Hudson. For children and other vulnerable populations, the effects can be even more intense, with risks including dehydration, pneumonia, and in severe cases, inflammation of the brain and heart.
This outbreak is not confined to the United States; the H3N2 subclade K strain has also led to severe flu seasons in countries like Australia, Japan, the United Kingdom, and various regions across Europe and Asia.
What do you think about the rising flu cases and the effectiveness of the vaccine? Are you among those who believe getting vaccinated is vital, or do you have reservations about its efficacy? Share your thoughts in the comments!
