Updated October 13, 2026, 9:20 p.m. ET
Fall may have only officially begun, but the titular illness of “flu and cold season” seems to be off to a good start compared to previous years.
The flu began hitting parts of the United States earlier this year than in the past five years, with an initial outbreak in late August to early September, according to the Centers for Disease Control and Prevention. While flu season typically begins in earnest around November, data used to track respiratory illnesses — like lab tests, hospitalizations and wastewater data — detected activity while summer temperatures were still scorching.
“Every year we start seeing cases at the end of the year, usually peaking in late winter. Over the last couple of weeks, in early October, I’ve seen an uptick in influenza A,” Dr. Carla Garcia Carreno, an infectious disease specialist at Children’s Health, a pediatric health care network in Texas, told USA TODAY. “This is an unusually early start to the flu season.”
Wondering if this means you need to change your vacation plans, your filming schedule, or prepare for a particularly difficult holiday season? Here’s what we know.
How many cases of flu have been reported nationwide?
Flu cases began to take off in early fall this year, reaching a level of activity in October usually seen before December or January, according to wastewater data.
As of October 7, CDC projections revealed that flu infections were increasing in 50 states. The highest activity occurs on the West Coast, particularly in areas that cover Arizona, California, Hawaii, Nevada, Alaska, Idaho, Oregon and Washington.
Influenza activity detected in wastewater was still classified as “very low” nationally as of October 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 was not specified how long this gap would last.
CDC data through Oct. 3 also showed that about 3.6% (1,435) of 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 influenza. Hospitalizations remained low.
Wastewater data maintained by WasteWaterSCAN, a Stanford University-led tool for tracking the spread of disease, classified flu activity as “high” nationally, meaning higher concentrations of the virus were detected in wastewater from more communities nationwide.
The same data shows the earliest onset of influenza in at least the last four years; samples positive for influenza A were 60% for the month to October 13, compared to only 20% in October 2025.
The CDC also noted that seasonal flu activity began to increase between late August and early September.
Influenza activity maps by state
Where flu cases are increasing: map
What is the most common flu strain and what are the symptoms?
Currently, influenza A is the dominant strain. Influenza A is the most common type of flu that circulates seasonally and produces the symptoms we most often associate with being “flu,” such as fever, cough, and runny nose. Influenza B also appears during flu season, but usually does not account for as many cases.
The subclade (a subtype or group of disease) A(H1N1)pdm09 was the most detected by the CDC this season. This may sound familiar as the strain that caused the “swine flu” pandemic in 2009, back when it was a new virus. Today, this is part of a typical flu season.
Influenza A mutates more quickly than other types, which is why it has many subtypes and is best known for causing epidemics and clusters of serious illnesses. Influenza A and how quickly it can evolve is a key factor in why the flu vaccine is reformulated each season to target that year’s strains and subtypes.
Last year, for example, a newly mutated type of influenza A, known as subclade K, caused a stir by generating cases and escaping the season’s targeted firing.
According to the Mayo Clinic and the CDC, symptoms of the flu, including the more common influenza A, include:
- Fever
- Aches and chills
- Cough
- Runny or stuffy nose and sneezing
- Sore throat
- Headache
- Fatigue
- Loss of appetite and stomach upset
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 ward off contagious diseases, according to the CDC. This applies to all of the above illnesses and others that often circulate in winter, such as respiratory syncytial virus, or RSV.
Health agencies recommend washing your hands with warm, soapy water for at least 20 seconds. It is also important to wash them before and after eating, before and after handling food, after using the toilet, and after being around sick people or touching surfaces that may be contaminated. Wearing a mask when sick or traveling during illness season can also help prevent the spread.
“Everything we apply to prevent respiratory viruses applies to flu prevention,” Carreno said. “These measures include: proper hand washing, not sharing utensils or other personal items, staying home when sick, preventing large indoor gatherings.”
This is especially important for people at risk of more severe illness, including children and the elderly, pregnant people, immunocompromised people, and those with underlying conditions such as obesity and diabetes.
“Early recognition of possible influenza infection is also very important. Influenza can present like other viruses causing a cold-like illness, but it usually presents with higher fever, sore throat, muscle pain, headache and may have gastrointestinal symptoms,” she said.
Complications from the flu can occur, especially in children, and can include conditions such as encephalitis, myocarditis, pneumonia, and Guillain-Barré syndrome. For this reason, Carreno suggests that parents or guardians who suspect the flu should see their child or loved one’s doctor early for preventative treatment 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 vaccine? Who is eligible?
Major medical groups stepped in last month to clear up 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 the flu and a handful of other illnesses, including meningococcal disease, COVID-19 and hepatitis A and B.
A federal judge blocked some of those changes in March, particularly those regarding COVID-19 and hepatitis B vaccinations, 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 unsubstantiated claims about vaccines without evidence.
The guidelines were released through a partnership between leading medical groups, including the American Academy of Pediatrics (AAP), the American Academy of Family Physicians (AAFP), the American College of Obstetricians and Gynecologists (ACOG), and the Infectious Diseases Society of America (IDSA), and suggest that everyone six months or older (including pregnant people) should get vaccinated annually, with some exceptions for people with certain medical conditions. People 65 and older should receive a higher dose, if possible.
People over 18 can still go to their local pharmacy and get a flu shot, at their discretion. Parents who wish to vaccinate their children should check with their pediatrician and local pharmacy to ensure all requirements are met.
“The American Academy of Pediatrics recommends receiving the annual flu vaccine by the end of October. However, given the early start to this season, early vaccination is suggested,” Carreno said. “After vaccination, it takes about two weeks to build up protection.”
Children under 9 years old, meaning they are in the highest risk group for severe illness, should be vaccinated with two doses of the vaccine, four weeks apart, if they have never been vaccinated against the flu, she added.
This story has been updated to clarify wastewater data.
Gn Health
