Flu is hitting unusually early in parts of the West, catching doctors by surprise as some hospitals see levels of illness more typical of early winter, when the respiratory virus season normally gets underway.
Across Seattle Children’s hospital system, about 150 children have tested positive for influenza in the past two weeks, a level the system typically does not see until early December. By comparison, for the same time period last fall, the health system had about 10 flu cases, said Danielle Zerr, who heads the pediatric infectious diseases division. The percentage of flu tests coming back positive has also risen sharply, signaling that the virus is spreading more widely in the community.
The flu season generally is considered to begin around Oct. 1 and clinicians typically advise people to get their vaccines by the end of October. Even though it is too early to know whether the September activity foreshadows a severe flu season or is an unusual surge that could subside, epidemiologists and clinicians are encouraging patients to get their shots sooner instead of waiting.
“We’re about two months early. So this is really concerning because people haven’t been working hard to get their vaccines quite yet,” Zerr said. “The way flu is circulating now, you wanted that vaccine in you two weeks ago, if not even a little before that.”
Seattle Children’s is also seeing an increase in covid-19 cases, Zerr said. But that rise is less unusual: covid-19 is less seasonally predictable than flu, with transmission surging at different points of the year.
Other signs of unusually early flu activity are emerging across the West. Southern Nevada health officials last week reported their first flu-related death of the season, a man in his 50s with underlying health conditions. In addition to Washington state, Alaska, California and Hawaii are also reporting sharp increases in the percentage of laboratory tests coming back positive for influenza.
“Consider encouraging patients to get vaccinated as soon as possible, rather than waiting until later in the season, particularly in the Western region,” wrote Caitlin Rivers, an epidemiologist who tracks outbreak-prone pathogens in a weekly newsletter, FOI Clinical, for clinicians and public health practitioners.
Spread of covid-19 cases remains uneven across U.S.
Scientists do not know what is driving the early rise. Flu activity remains low nationally, according to the Centers for Disease Control and Prevention. Health officials caution against drawing broad conclusions from what is happening in a handful of places. They are watching increased influenza activity in parts of Asia, including Japan, as well as changes in the strains circulating this year. International travel could also help viruses move quickly between countries.
The CDC assesses the severity of each flu season based on three indicators: visits to doctors’ offices and clinics for influenza-like illnesses, flu-related hospitalizations and flu deaths. The agency expects this flu season to be of moderate severity overall, although it cautions that there is considerable uncertainty this early. Last season was considered moderate across all ages but was classified as high severity for children.
As of Sept. 30, the CDC’s Center for Forecasting and Outbreak Analytics estimates that influenza infections are growing or likely growing in 48 states, declining or likely declining in one state, and not changing in one state.
Flu seasons can vary widely in their timing and severity, depending in part on which strains are circulating and how much immunity people have from previous infections and how well the vaccine is matched to circulating viruses.
Seasons dominated by H3N2 viruses have historically tended to be more severe, particularly for older adults. Early surveillance in Washington this fall shows H1N1 predominating.
Helen Chu, an infectious-diseases professor at the University of Washington, said the shift could help explain why flu is taking off so early. H3N2 dominated last season, meaning people may have less recent immunity against H1N1, she said. Whether that is actually driving the early spread — and what it might mean for the months ahead — remains unclear.
Flu seasons are notoriously difficult to predict from year to year, said Robert Hopkins, medical director for the National Foundation for Infectious Diseases and an infectious diseases physician in Little Rock.
Hopkins said there have been a few more influenza cases this fall than usual, but not a dramatic increase. And so far, there have been more covid-19 cases than flu in his region, he said.
Nationally, the summer covid wave appears to be leveling off or declining, and hospitalizations remain low. Unlike flu, which generally follows a fall-and-winter pattern, covid circulates year-round and has repeatedly produced waves in both summer and winter.
Transmission remains uneven. As of Sept. 30, the CDC estimated that infections were rising in 19 states, falling in eight and holding steady in 23. Wastewater data show elevated levels in parts of the West and increases in parts of the Northeast, including New York City and surrounding counties.
RSV remains very low nationally, although Florida — where RSV activity often begins earlier — is reporting increases in RSV-related emergency-room visits and hospital admissions among children younger than 5.
For clinicians at Seattle Children’s, however, the timing is unmistakably unusual. September simply does not normally look like this.
“The flu came so early this year that all the people who would normally get vaccinated might just not have had the opportunity yet or just hadn’t taken the opportunity to do it,” said Seattle Children’s Zerr. In addition, she said there are some who are hesitant or reluctant to get the shots.
Flu vaccines for the 2026-27 season are already widely available. Influenza vaccines are less effective in preventing infections than other vaccines such as the one for measles, mumps and rubella, which the CDC says prevents measles in about 97 percent of cases when patients have received two doses. But multiple studies have shown the flu vaccine reduces the disease’s severity and averts hospitalizations and deaths.
The 2024-25 flu season was especially harsh, and the CDC estimates there were 51 million influenza-related illnesses and 45,000 deaths, including 298 pediatric deaths.
In 2023, the CDC launched a flu vaccine campaign called Wild to Mild to advertise how getting a flu vaccine reduces flu risk. But Health Secretary Robert F. Kennedy Jr. ordered the CDC to halt promotions for that ad campaign early last year.
Unlike in previous years, the CDC has not launched a broad public campaign this fall urging Americans to get their flu shots, even as unusually early activity is emerging in parts of the West. The vaccine takes about two weeks to build protection.
Kennedy has disparaged the flu shot or linked it to his voice condition at least two dozen times over the last six years. Early this year, the federal government reversed course and revised vaccination guidelines to no longer recommend routine flu shots for children and adolescents as part of an overhaul of the pediatric immunization schedule.
But that action, along with other vaccine policy changes under Kennedy, was put on hold by a federal judge in March. The CDC’s influenza website currently recommends annual vaccinations for nearly everyone 6 months and older, generally advising people to get vaccinated in September or October.
The website, updated Sept. 1, has a note at the top saying: “Because of legal uncertainties and inquiries, the CDC states the recommendations for seasonal influenza vaccination from the July 2025 immunization schedule remain in effect for the 2026-2027 influenza season.”
Asked if the CDC plans a public campaign urging flu vaccination, Emily Hilliard, a spokesperson for the Department of Health and Human Services, said in a statement that the CDC is “developing a communications strategy to provide clear, accessible information about influenza vaccination and other critical steps people can take to protect themselves during respiratory virus season.” She said this includes information “about the benefits and risks of vaccination to support informed decision-making.”
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