Acute Febrile Illness: All You Need To Know About Causes, Symptoms And Treatment Of AFI
Where Is Flu Surging In The US? Some Hospitals Are Overwhelmed In States With High Rates
Flu is still spreading across United States amid a winter wave of seasonal illnesses. In early February, doctor visits for influenza symptoms and flu-related hospitalizations hit a 15-year high. The tough flu season is straining many hospitals, leading to overflowing emergency rooms, long wait times, and limits on patient visitors.
What's more, flu outbreaks among children have forced schools to close in multiple states.
The 2024–2025 flu season — which has sickened over 33 million Americans so far — is in full force. There's more to come before we're beyond the peak, according to experts.
Seasonal flu activity remains elevated and this season is now considered "high severity," the U.S. Centers for Disease Control and Prevention said in its FluView report for the week ending Feb. 15.
Currently, 42 states and the District of Columbia are reporting "very high" or "high" levels of influenza-like illness activity, per the CDC's most recent data. The South, Southeast and Midwest regions are being hit especially hard.
A record number of people are seeking care. Outpatient visits for flu-like illness have not been this high seen since the 2009-2010 flu season, during the swine flu pandemic.
"We are right now in the middle of a nationwide epidemic of seasonal influenza that is filling emergency rooms," Dr. William Schaffner, professor of infectious diseases at Vanderbilt University School of Medicine, tells TODAY.Com.
The flu is a common and highly contagious respiratory illness caused by influenza viruses.
The majority of the cases in the U.S. Are being caused by influenza A, primarily the H3N2 and H1N1 strains, according to the CDC. Flu A tends to be more aggressive in adults and hit earlier than flu B, but flu B can surge later in the season.
The tough flu season comes as the country also sees waves of norovirus, COVID-19, and respiratory syncytial virus or RSV — which some have dubbed a "quad-demic." While it's expected to see these four viruses surge in the winter, the surge in respiratory illness is overwhelming some health facilities.
The 2025 flu seasonIn the U.S., flu activity tends to peak between December and February, per the CDC. However, the 2024-2025 flu season began later than usual.
After a slow start, influenza activity started increasing dramatically in early December, says Schaffner, and after a slight dip around the holidays, has "taken off" since. According to CDC data, flu activity appears to be stabilizing after peaking for a second time in late January.
So far, the CDC estimates there have been at least 33 million illnesses, 430,000 hospitalizations and 19,000 deaths from flu this season. This includes 86 pediatric deaths.
Currently, positive laboratory tests, outpatient and emergency department visits, hospitalizations and flu-related deaths are all high, CDC data show.
As of data posted Feb. 21, emergency department visits for influenza are "very high" nationally, according to the CDC. Flu-related hospitalizations are higher than they have been during any peak week going back to the 2010-2011 flu season.
Wastewater surveillance is also showing very high levels of flu activity across the U.S. According to WastewaterSCAN, which monitors viruses through municipal water systems, influenza A is in the "high" category nationwide as of Jan. 26. Flu B remains lower but positive detections are rising, a spokesperson for WastewaterSCAN tells TODAY.Com.
It's unclear how the rest of flu season will pan out, and it's too soon to tell how its severity will compare to past seasons, experts say.
"We're in the midst of influenza and it's bad, but whether it's different than previous years, we won't know that for months," Dr. Jason Newland, the Division Chief of Infectious Diseases at Nationwide Children's Hospital, tells TODAY.Com.
The 2023-2024 flu season was "moderately severe," and caused an estimated 40 million illnesses and 28,000 deaths, per the CDC. "Last year, we had over 200 pediatric deaths from flu, that was a really bad year," says Newland.
Where is flu surging in U.S.?
Map of outpatient influenza-like illness activity in U.S. For 2024-25 flu seasonCDC The following U.S. States reported "very high" influenza-like illness activity during the week ending Feb. 15, according to the latest CDC data:
The District of Columbia and New York City are also reporting very high levels of influenza activity, per CDC data.
Some hospitals feel strained as flu cases riseEvery winter, hospitals fill up around this time of year due to respiratory illnesses, and this year is no exception.
In early February, the weekly flu hospitalization rate reached a record high of 12.8 per 100,000 — this is the highest peak weekly rate observed during all flu seasons since 2010, per CDC data.
Hospital bed occupancy for influenza increased to 5% during the week ending Feb. 8, up from 2.8% the first week of January, per the latest data from the CDC's National Healthcare Safety Network.
The surge in flu cases, along with other seasonal viruses, is overwhelming some hospitals.
Tennessee is one of several states currently experiencing the highest levels of flu activity in the U.S.
"My hospital is jammed," says Schaffner, who is based in Nashville. "We have people on stretchers, on gurneys in the emergency room waiting to be admitted, and this is true across the country."
California is also being hit hard. San Diego in particular is seeing a steady rise in flu cases and hospitalizations, Dr. Francesca Torriani, an infectious disease specialist at UC San Diego Health, tells TODAY.Com. Compared to this time last year, flu-related emergency department visits are nearly double that of last year in San Diego County, she says.
Also in San Diego, Sharp Chula Vista Medical Center deployed a temporary tent outside their emergency department to triage and treat low-risk patients in response to high volumes of patients with flu symptoms. The hospital could treat 15-20 flu patients per day in the tent, which helped open the availability of beds in the ER for other health concerns, Sharp HealthCare told TODAY.Com on Jan. 15.
Louisiana is another influenza hot spot. Janz, who works with LCMC hospitals in New Orleans, says the number of patients hospitalized and in the ICU with influenza has jumped by about 30% since December.
"We're able to deal with that influx pretty well," says Janz. However, he notes that the surges in flu-like illnesses can quickly strain hospitals already busy with other patients.
In South Carolina, three major hospital systems tightened visitor restrictions due to increased influenza, NBC affiliate WYFF4 reported on Jan. 16. Spartanburg Regional Healthcare System, Prisma Health and Bon Secours St. Francis began restricting children under 16 and anyone with flu symptoms from visiting hospitalized patients as a safety measure.
Flu is also surging in the Midwest, especially in Ohio. Amid a backdrop of increased RSV and COVID-19 activity, "our hospitals get really busy," says Newland, who works in Columbus. However, according to Newland, this year's flu season is less of an outlier and more of a return to pre-pandemic numbers.
Although older adults are driving most hospitalizations, flu is hitting people of all ages. Flu cases among children are surging, crowding pediatrician's offices and forcing school closures in multiple states.
As flu activity continues, experts warn that ER wait times and bed availability may be affected. "We've got a lot of work left to do for this season, and it still puts all these hospitals at risk," says Janz.
Influenza symptomsFlu symptoms can range from mild to severe. Common flu symptoms include:
"People are going to feel bad for a few days, but it's something that usually people can ride out at home," says Janz.
Some people are at higher risk of developing severe illness or complications due to influenza. According to the CDC, these include but are not limited to:
Most people will recover from flu without treatment, the experts note. Supportive care such as rest, fluids and over-the-counter medication can help manage symptoms.
The CDC recommends staying home for at least 24 hours until after your fever is gone, except to seek medical attention.
Flu can be treated with antiviral drugs, such as Tamiflu, which are especially important for people at higher risk of severe illness, the CDC says. These require a prescription and are most effective when taken within 48 hours after symptoms begin.
If you are in a high-risk group, feel very sick or have any concerns about flu season, contact your doctor. "They can walk you through when to go and when to not to go in," says Newland.
In some cases, going to the emergency room may be necessary.
"If people start having difficulty breathing, or if people start getting confused or having really high fevers, or they're unable to eat or drink for days ... I would recommend people seek health care," says Janz.
How to protect against fluIt's not too late to get your annual flu shot, NBC News medical correspondent Dr. Natalie Azar told TODAY in a segment aired Tuesday, Feb. 18.
The influenza vaccine can help protect against flu and its complications, which is especially important for high-risk individuals. It's recommended by the CDC for everyone ages 6 months and older.
The flu shots for the 2024-2025 season include three flu viruses: two flu A strains (H1N1 and H3N2) and one influenza B strain. Flu B can surge later in the flu season, so the flu shot can offer continued protection for months, TODAY.Com previously reported.
In addition to getting your flu shot, you can protect yourself and others by taking the following steps:
How Are H5N9 And H5N1 Different? What To Know After California Bird Flu Outbreak
A California duck farm made headlines this week after the World Organization of Animal Health published a report by U.S. Authorities that a strain of bird flu that scientists call H5N9 had been found among sick birds in the flock.
This is far from the first time that H5N9 has been found in birds around the country. But the U.S. Department of Agriculture said it was the first time that H5N9 had been found in American poultry sick with "highly pathogenic avian influenza," meaning it caused severe disease.
"Clinical signs included increased mortality. State officials have quarantined the affected premises," the USDA said of the flock.
What is H5N9 and how is it different from H5N1?Scientists classify bird flu viruses by which kind of two key proteins are inside of them: the hemagglutinin, like H5 or H3, and the neuraminidase, like N1 or N9.
Different blends of those two proteins alongside many other mutations elsewhere in the virus can affect how sick people and animals get and how it spreads.
H5N1 has been the dominant grouping of strains fueling this past year's outbreaks in the U.S., with different variants of that virus spreading in wild birds, poultry flocks, dairy cattle, pets and into at least 67 confirmed human cases.
A spokesperson for the department said that scientists believe the H5N9 was the result of a "reassortment," where H5N1 was able to genetically mix with other influenza viruses inside of a duck.
"The finding was not unexpected, as it is not uncommon to see reassortments and ducks are reservoir hosts for influenza A viruses," the spokesperson said.
Both H5N9 and H5N1 were found to be infecting ducks at the farm, the USDA said.
"The H5N1 virus is widely circulating across North America, and these viruses can reassort in species that are susceptible to influenza viruses," said S. Mark Tompkins, director of the Center for Influenza Disease and Emergence Research at the University of Georgia. He agreed that it would not be "terribly surprising" to see a reassortment emerge to infect poultry.
"H5N1 reassorts with other avian influenza viruses quite frequently and even the current H5 HA protein that is infecting dairy cows and commercial poultry farms in the US has been shown to reassort," Andy Pekosz, professor of microbiology and immunology at Johns Hopkins University, wrote in an email.
Has H5N9 been seen in the U.S. Before?H5N9 has been seen before in U.S. Birds, but often it results in less severe symptoms, called "low pathogenic avian influenza" by veterinarians.
"H5N9 viruses have been detected in North American wild birds in 2023 and 2024, and before the current outbreak," said Tompkins.
Some of the earliest records of H5N9 around the world date back to turkeys infected in Wisconsin in the 1960s, which U.S. Officials reported had "mild respiratory symptoms and a severe drop in egg production."
The California duck farm's strain of H5N9 is different from those earlier cases because this time it is closely related to a newer variant of the H5N1 virus. That variant is called H5N1 D1.1, the USDA spokesperson said, which has emerged over the past year to dominate U.S. Cases in wild birds and poultry.
"The combination H5N9 is not new and other versions, like H5N5 also exist. Just because this was now detected, doesn't mean trouble necessarily," said virologist Florian Krammer, professor at the Icahn School of Medicine at Mount Sinai, in an email.
Krammer pointed to recent detections of the H5N5 strain spreading from Europe, and then jumping from birds to be able to infect mammals across Canada as prompting more worry for him.
"It's not really surprising, because we have a history of three years of H5N1 undergoing reassortments that would typically burn out and not emerge as a major one," said David Swayne, a private veterinarian and former director of the USDA's Southeast Poultry Research Laboratory.
Swayne said that past H5N9 outbreaks have been dead ends, in the handful of times they have been found to be causing severe disease in ducks.
"So far, I have not heard of any evidence to say this H5N9 has some kind of fitness that is better than the H5N1. If it doesn't have that, it can't outcompete," said Swayne.
Is H5N9 a bigger risk to humans than H5N1?As with H5N1, H5N9 in birds would still need to achieve some key mutations before it is able to spread efficiently among humans.
The Centers for Disease Control and Prevention said Monday they have found no evidence of human-to-human transmission of bird flu in the U.S. To date. Most cases were blamed on direct contact with sick animals, except for three that have befuddled investigators who failed to identify a likely source.
It is unclear whether authorities followed up with workers at the Merced County farm about potential human infections. A spokesperson for the county did not immediately respond to a request for comment.
If H5N9 gains a foothold in humans, people may possibly have less immunity to the virus than they do to H5N1.
"The seasonal, human H1N1 virus has an NA protein that is related, but different from the bovine H5N1 NA protein. There is some cross-recognition of avian H5N1 NA in the human population because of this," said Pekosz.
Where was the California H5N9 outbreak?The USDA said the virus was detected at a "commercial duck meat" farm in California's Merced County, in an outbreak that started on Nov. 23, 2024.
A total of 118,954 birds were culled at the duck farm by Dec. 2 to stamp out the virus, in an effort to curb the risk of further bird flu spread.
More than 3 million birds have been culled at farms in this California county over the past year due to bird flu outbreaks, the most of any county in the state. California has been hit hard by this past year's bird flu outbreaks, which have resulted in record cullings across the egg industry.
Scientists say ducks are especially susceptible to harboring influenza viruses without being sick, making them common mixing vessels for bird flu strains.
"Unless you have very tight biosecurity, it is very hard to raise ducks without many low path influenza viruses," said Swayne.
Swayne said ducks often need the lowest dose of virus to be infected with bird flu viruses, compared to other poultry, like chickens. One way the virus can spread onto farms is when they are raised outside, mixing with wild ducks.
"If you look at the natural history, wild ducks are the reservoir of genes for all influenza virus. There's probably an adaptation with the virus. These viruses infect without showing overt clinical disease, they spread very rapidly between the adults to the juveniles," said Swayne.
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KFF Health News —
Sonya Stokes, an emergency room physician in the San Francisco Bay Area, braces herself for a daily deluge of patients sick with coughs, soreness, fevers, vomiting, and other flu-like symptoms.
She's desperate for information, but the Centers for Disease Control and Prevention, a critical source of urgent analyses of the flu and other public health threats, has gone quiet in the weeks since President Donald Trump took office.
"Without more information, we are blind," she said.
Flu has been brutal this season. The CDC estimates at least 24 million illnesses, 310,000 hospitalizations, and 13,000 deaths from the flu since the start of October. At the same time, the bird flu outbreak continues to infect cattle and farmworkers. But CDC analyses that would inform people about these situations are delayed, and the CDC has cut off communication with doctors, researchers, and the World Health Organization, say doctors and public health experts.
"CDC right now is not reporting influenza data through the WHO global platforms, FluNet [and] FluID, that they've been providing information [on] for many, many years," Maria Van Kerkhove, interim director of epidemic and pandemic preparedness at the WHO, said at a Feb. 12 press briefing.
"We are communicating with them," she added, "but we haven't heard anything back."
On his first day in office, President Donald Trump announced the U.S. Would withdraw from the WHO.
A critical analysis of the seasonal flu selected for distribution through the CDC's Health Alert Network has stalled, according to people close to the CDC. They asked not to be identified because of fears of retaliation. The network, abbreviated as HAN, is the CDC's main method of sharing urgent public health information with health officials, doctors, and, sometimes, the public.
A chart from that analysis, reviewed by KFF Health News, suggests that flu may be at a record high. About 7.7% of patients who visited clinics and hospitals without being admitted had flu-like symptoms in early February, a ratio higher than in four other flu seasons depicted in the graph. That includes 2003-04, when an atypical strain of flu fueled a particularly treacherous season that killed at least 153 children.
Without a complete analysis, however, it's unclear whether this tidal wave of sickness foreshadows a spike in hospitalizations and deaths that hospitals, pharmacies, and schools must prepare for. Specifically, other data could relay how many of the flu-like illnesses are caused by flu viruses — or which flu strain is infecting people. A deeper report might also reveal whether the flu is more severe or contagious than usual.
"I need to know if we are dealing with a more virulent strain or a coinfection with another virus that is making my patients sicker, and what to look for so that I know if my patients are in danger," Stokes said. "Delays in data create dangerous situations on the front line."
Although the CDC's flu dashboard shows a surge of influenza, it doesn't include all data needed to interpret the situation. Nor does it offer the tailored advice found in HAN alerts that tells health care workers how to protect patients and the public. In 2023, for example, a report urged clinics to test patients with respiratory symptoms rather than assume cases are the flu, since other viruses were causing similar issues that year.
"This is incredibly disturbing," said Rachel Hardeman, a member of the Advisory Committee to the Director of the CDC. On Feb. 10, Hardeman and other committee members wrote to acting CDC Director Susan Monarez asking the agency to explain missing data, delayed studies, and potentially severe staff cuts. "The CDC is vital to our nation's security," the letter said.
Several studies have also been delayed or remain missing from the CDC's preeminent scientific publication, the Morbidity and Mortality Weekly Report. Anne Schuchat, a former principal deputy director at the CDC, said she would be concerned if there was political oversight of scientific material: "Suppressing information is potentially confusing, possibly dangerous, and it can backfire."
CDC spokesperson Melissa Dibble declined to comment on delayed or missing analyses. "It is not unexpected to see flu activity elevated and increasing at this time of the year," she said.
A draft of one unpublished study, reviewed by KFF Health News, that has been withheld from the MMWR for three weeks describes how a milk hauler and a dairy worker in Michigan may have spread bird flu to their pet cats. The indoor cats became severely sick and died. Although the workers weren't tested, the study says that one of them had irritated eyes before the cat fell ill — a common bird flu symptom. That person told researchers that the pet "would roll in their work clothes."
After one cat became sick, the investigation reports, an adolescent in the household developed a cough. But the report says this young person tested negative for the flu, and positive for a cold-causing virus.
Corresponding CDC documents summarizing the cat study and another as-yet unpublished bird flu analysis said the reports were scheduled to be published Jan. 23. These were reviewed by KFF Health News. The briefing on cats advises dairy farmworkers to "remove clothing and footwear, and rinse off any animal biproduct residue before entering the household to protect others in the household, including potentially indoor-only cats."
The second summary refers to "the most comprehensive" analysis of bird flu virus detected in wastewater in the United States.
Jennifer Nuzzo, director of the Pandemic Center at Brown University, said delays of bird flu reports are upsetting because they're needed to inform the public about a worsening situation with many unknown elements. Citing "insufficient data" and "high uncertainty," the United Kingdom raised its assessment of the risk posed by the U.S. Outbreak on dairies.
"Missing and delayed data causes uncertainty," Nuzzo said. "It also potentially makes us react in ways that are counterproductive."
Another bird flu study slated for January publication showed up in the MMWR on Feb. 13, three weeks after it was expected. It revealed that three cattle veterinarians had been unknowingly infected last year, based on the discovery of antibodies against the bird flu virus in their blood. One of the veterinarians worked in Georgia and South Carolina, states that haven't reported outbreaks on dairy farms.
The study provides further evidence that the United States is not adequately detecting cases in cows and people. Nuzzo said it also highlights how data can supply reassuring news. Only three of 150 cattle veterinarians had signs of prior infections, suggesting that the virus doesn't easily spread from the animals into people. More than 40 dairy workers have been infected, but they generally have had more sustained contact with sick cattle and their virus-laden milk than veterinarians.
Instead, recently released reports have been about wildfires in California and Hawaii.
"Interesting but not urgent," Nuzzo said, considering the acute fire emergencies have ended. The bird flu outbreak, she said, is an ongoing "urgent health threat for which we need up-to-the-minute information to know how to protect people."
"The American public is at greater risk when we don't have information on a timely basis," Schuchat said.
This week, a federal judge ordered the CDC and other health agencies to "restore" datasets and websites that the organization Doctors for America had identified in a lawsuit as having been altered. Further, the judge ordered the agencies to "identify any other resources that DFA members rely on to provide medical care" and restore them by Feb. 14.
In their letter, CDC advisory committee members requested an investigation into missing data and delayed reports. Hardeman, an adviser who is a health policy expert at the University of Minnesota, said the group didn't know why data and scientific findings were being withheld or removed. Still, she added, "I hold accountable the acting director of the CDC, the head of HHS, and the White House."
Hardeman said the Trump administration has the power to disband the advisory committee. She said the group expects that to happen but proceeded with its demands regardless.
"We want to safeguard the rigor of the work at the CDC because we care deeply about public health," she said. "We aren't here to be silent."
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