Fall may have just officially begun, but the titular illness of "flu and cold season" seems to have gotten a jump start on previous years.
The flu has begun hitting parts of the U.S. earlier this year compared to the last five years, first picking up in late August to early September, according to the Centers for Disease Control and Prevention. While flu season typically starts in earnest around early October, data used to track respiratory illnesses – like laboratory tests, hospitalizations and wastewater data – detected activity while summer temps were still scorching.
"Every year, we start seeing cases at the end of the year, with a peak usually in late winter. Over the past two weeks, early October, I have seen a slight increase in Influenza
A," Dr. Carla Garcia Carreno, Infectious Disease Specialist at Children's Health, a pediatric health care network in Texas, told USA TODAY. "This is an unusual early start to the influenza season."
Wondering if this means you need to change your vacation plans, shot schedule or prepare for a particularly rough holiday season? Here's what we know.
How many flu cases were reported nationwide?
Flu cases began to take off in early fall this year, reaching an activity level in October not usually seen until December or January, according to wastewater data.
As of Oct. 7, CDC projections found that flu infections were on the rise in 50 states. The highest activity is occurring on the West Coast, specifically the regions that cover Arizona, California, Hawaii, Nevada, Alaska, Idaho, Oregon and Washington.
Flu activity detected from wastewater was still categorized as "very low" nationwide as of Oct. 3, according to the CDC. The CDC noted that wastewater data tracking is experiencing a "brief gap" in updates due to a new contract with a testing company. It did not clarify how long this gap would last.
CDC data through Oct. 3 also showed that about 3.6% (1,435) of the 39,317 flu tests administered that week were reported positive to the National Respiratory and Enteric Virus Surveillance System. The vast majority of these confirmed illnesses (97%) were influenza A, the most common form of the flu. Hospitalizations remained low.
Wastewater data maintained by WasteWaterSCAN, a Stanford University-led tool for tracking the spread of disease, categorized flu activity as "high" nationally, meaning higher concentrations of the virus have been detected in the wastewater of more communities nationwide.
The same data shows the earliest onset of flu in at least the last four years; samples positive for influenza A were at 60% for the month as of Oct. 13, compared to just 20% in October 2025. The program also began detecting the rise of flu cases in early October, compared to January for the 2025-2026 and 2023-2024 seasons, December for the 2022-2023 season, and March for the 2024-2025.
The CDC likewise noted that seasonal flu activity began increasing around late August to early September.
Maps of flu activity by state
Where flu cases are on the rise: map
What is the most prominent flu strain and what are the symptoms?
Currently, influenza A is dominant as the number one strain. Influenza A is the most common type of flu that circulates seasonally and produces the symptoms we most often associate with being "flu-like," such as fever, cough and runny nose. Influenza B also appears during flu season, but usually doesn't account for as many cases.
The subclade (a subtype or group of an illness) A(H1N1)pdm09 has been he most detected by the CDC this season. It may sound familiar as the strain that caused the "swine flu" pandemic in 2009, back when it was a new virus. Now, it is part of a typical flu season.
Influenza A mutates faster than other types, which is why it has many subtypes and is best known for causing outbreaks and major illness clusters. Influenza A and how rapidly it can change is a driving factor behind why the flu shot is reformulated each season to target the year's strains and subtypes.
Last year, for example, a newly mutated influenza A type known as subclade K caused a stir as it drove cases and evaded the season's target shot.
According to Mayo Clinic and CDC, symptoms of flu, including the most common influenza A, include:
- Fever
- Body aches and chills
- Cough
- Runny or stuffy nose and sneezing
- Sore throat
- Headache
- Fatigue
- Loss of appetite and upset stomach
How to protect yourself from the flu.
You may be tired of hearing it, but the old cliché is true: Washing your hands well – and often – is one of the best ways to keep contagious illnesses at bay, according to the CDC. This applies to all the ailments above and others that often circulate during the wintertime, like respiratory syncytial virus, or RSV.
Health agencies recommend washing your hands with hot, soapy water for at least 20 seconds. It's also important to wash them before and after eating, before and after handling food, after using the bathroom and after being around sick people or touching surfaces that could be contaminated. Mask-wearing while sick or out and about during illness season can also help prevent the spread.
"Everything we apply to prevent respiratory viruses applies to preventing Influenza," Carreno said. "These measures include: good hand washing, not sharing utensils or other personal items, staying home if sick, preventing large indoor gatherings."
This is especially important for people at risk of more serious disease, including children and older people, pregnant people, and immunocompromised people and those with underlying conditions like obesity and diabetes.
"Early recognition of possible Influenza infection is also very important. Influenza might present like other viruses causing a common cold type of illness, but usually presents with higher fever, sore throat, muscle pain, headache, and can have gastrointestinal symptoms," she said.
Influenza complications can happen, especially in children, and may include conditions like encephalitis, myocarditis, pneumonia and Guillain-Barré syndrome. Because of this, Carreno suggests that parents or caregivers who suspect influenza should consult with their child's or loved one's doctor early for preventive medicine and early intervention.
The most effective way to prevent serious illness from the flu is vaccination, according to the World Health Organization, CDC and other leading medical institutions.
Should you get the flu shot? Who is eligible?
Top medical groups stepped in last month to address confusion around vaccines with a set of independent recommendations after the Trump administration limited COVID vaccine recommendations in 2025 and issued a memo in January 2026 removing universal recommendations for childhood vaccines that protect against flu and a handful of other diseases, including meningococcal disease, COVID-19 and hepatitis A and B.
A federal judge blocked some of these changes in March, specifically those concerning COVID-19 and Hep B immunizations, a decision the Department of Health and Human Services vowed to appeal. In August, President Donald Trump signed an executive order "calling for more vaccine flexibility and research" and fewer childhood vaccinations, repeating unsupported claims about vaccines without evidence.
The guidelines were released via a partnership between leading medical groups, including the American Academy of Pediatrics (AAP), American Academy of Family Physicians (AAFP), American College of Obstetricians and Gynecologists (ACOG) and the Infectious Diseases Society of America (IDSA), and suggest that everyone aged six months or older (including pregnant people) should get the shot yearly, with a few exceptions for people with certain medical conditions. People 65+ should recieve a higher dose, if possible.
People over the age of 18 can still walk into their local pharmacy and get a flu vaccine at their discretion. Parents looking to get their children vaccinated should check with their pediatrician and local pharmacy to ensure all requirements are met.
"The American Academy of Pediatrics recommends receiving annual Influenza immunization by the end of October. However, given the early start of this season, early vaccination is suggested," Carreno said. "After vaccination, it takes around two weeks to mount protection."
Children younger than 9, meaning they are among the highest risk group for serious illness, need to be immunized with two doses of the vaccine, four weeks apart, if they have never before been vaccinated for the flu, she added.
This article originally appeared on USA TODAY: Flu season is arriving months early. Here's where it's spreading
