Fueled by a new strain of the virus, the flu is hitting California early, and doctors warn the season could be especially tough for young children.
Concentrations of flu found in wastewater have risen sharply in the San Francisco Bay Area, and test positivity rates are rising in Los Angeles County And Orange Countyin accordance with state and county data. Hospitalizations and emergency room visits for the flu are also on the rise in Los Angeles and Orange counties.
“We're now at the point where we're starting to see a surge in flu cases. It's several weeks earlier than we typically see, but very similar to what we saw in the Southern Hemisphere with flu during the winter,” said Dr. Elizabeth Hudson, a regional physician and director of infectious diseases at Kaiser Permanente Southern California.
In Kaiser, flu cases have so far been reported mostly in clinics, but hospitalizations typically increase after Christmas. “We expect to see the same thing this year,” Hudson said.
“It appears that the number of cases earlier in the regular flu season was higher than we have seen in past years,” she added.
Flu levels are high in San Francisco wastewater, as well as in San Jose, Sunnyvale and Palo Alto wastewater. in accordance with WastewaterSCAN and Santa Clara County Department of Public Health.
One of the concerns this winter has been the rise of a relatively new influenza subvariant known as H3N2 subclade K, which emerged near the end of the summer. The move comes months after officials decided which strains to target in this fall's flu vaccine.
Subclade K “is driving an active early influenza season, with more cases being reported in some countries in the Northern Hemisphere,” the California Department of Public Health reports. said.
It remains unclear whether subclade K will reduce the effectiveness of this year's flu shot. Data recently released in the UK showed that this season's vaccines were 70% to 75% effective against flu hospitalizations in children and 30% to 40% effective in adults, which is within expectations, the US Centers for Disease Control and Prevention said. marked.
This suggests that “influenza vaccination remains an effective tool for preventing influenza-related hospitalizations this season,” according to the agency.
However, the expected effectiveness of the influenza vaccine against symptomatic illness caused by the new subvariant remains uncertain, the World Health Organization said.
Overall, flu rates in Los Angeles County remain relatively low but are increasing. Across California, flu hospitalizations are also low but increasing.
Nationally, severity rates remain low, according to the CDC.
However, the experience of other countries has some experts worried. another bad flu season may be on deck for California.
Australia's flu season, which is seasonally different from California's, arrived much earlier than usual, hit record levels and was particularly hard on the nation's children.
Japan, Taiwan and the UK also reported early flu season surges.
“Only time will tell whether this season will be more severe,” Hudson said of California. “We know we have a mutation … that can make the flu vaccine less effective. But the vaccine still provides excellent protection against hospitalization and death, even with a mutated strain in circulation.”
Given what has happened in the Southern Hemisphere, particularly in Australia, “we expect this season to have a disproportionate impact on children under 10 years of age,” Hudson said.
There have already been three flu-related deaths in children this season, including two Friday.
During the flu season, which ended in September, 280 children died from the flu — the highest level since the 2009–2010 swine flu pandemic season.
Overall, the 2024-25 season was ranked as the worst flu season since 2017-18 and hit adults hard. At least 38,000 people died from the flu. last seasonhealth authorities have calculated.
According to WHO, only slightly more than half of children who died from influenza had an underlying disease, and 89% of those who died were not vaccinated. CDC National Center for Immunization and Respiratory Diseases.
Among children who died from influenza last season, the most common complications Before death there were shock or sepsis, pneumonia, acute respiratory distress syndrome, seizures and brain damage.
Diagnosing the flu early can help prevent the worst of it by giving people who are sick time to take antiviral drugs such as Tamiflu. Three out of five children who died from influenza in the 2024-2025 season had never received antiviral drugs.
Emergency warning signs of flu complications children have breathing problems; bluish lips or face; the ribs retract with each breath; chest pain; severe muscle pain, in which the child may refuse to walk; dehydration, which includes no urine for eight hours or no tears when crying; convulsions; fever above 104 degrees that cannot be controlled with medication; fever or cough that gets better but returns or gets worse; and any fever in newborns younger than 12 weeks.
Since the official start respiratory virus season As of October 1, the CDC estimates there have been at least 1,900 flu-related deaths, 49,000 hospitalizations and 4.6 million cases of illness nationwide.
Doctors encourage everyone to get a flu shot—the CDC recommends it for everyone 6 months and older.
However, vaccination rates are lagging. Among children ages 6 months to 17 years, approximately 40.8% had been vaccinated as of the first week of December, according to the National Center for Statistics. National Immunization Survey. In the last season before the COVID-19 pandemic, the flu vaccination rate by this time of year was noticeably higher – 51.2%.
The study estimates that at the end of last flu season, only 49.8% of children and teens were vaccinated, compared with 62.4% who had received vaccinations by the end of the 2019-2020 flu season.
A decline in flu vaccinations has also been observed locally. “It is notable that fewer flu vaccines have been administered this year compared to the same period last year,” the Orange County Public Health Agency said. said.
It takes about two weeks for protection to build, but getting vaccinated as soon as possible before traveling or seeing friends and family “helps keep you and your loved ones safe,” the Los Angeles County Department of Public Health said in a statement to The Times.
