The flu season is now underway, and experts are warning it could be nasty year for the viral infection.
A mutated strain of the flu known as subclade K could roll across the U.S. this winter and spring. This form of the flu already has infected many people in countries such as Canada, Japan and the United Kingdom.
If the virus hits America hard, it will mark the second consecutive severe flu season. Last winter, the flu caused hospitalization rates to soar to levels not seen in 15 years.
Before the flu arrives in your community, find out what you need to know about the virus, including how to lower your risk of infection.
What is the flu?
The flu is a contagious respiratory illness that causes sickness that ranges from mild to potentially life-threatening.
Influenza viruses cause the flu. They often infect the nose and the throat, and sometimes spread to the lungs.
“One of the biggest mistakes people make about influenza is assuming it’s no more serious than a bad cold,” says Dr. Soma Mandal, a board-certified internist and women’s health specialist with Summit Health in New Providence, New Jersey.
While both colds and the flu are respiratory illnesses, the flu “tends to hit harder and more suddenly,” Mandal says.
“In some cases, it can spiral into serious complications,” she says, adding that the flu can cause organ failure and even death.
How do you catch the flu and what are the symptoms?
The flu mostly spreads through droplets from infected people who cough, sneeze or even just talk.
In most cases, flu symptoms affect a person suddenly. Such symptoms may include:
- Fever and chills
- Cough
- Sore throat
- Runny nose
- Muscle aches
- Headaches
- Fatigue
Children also might experience vomiting or diarrhea. These symptoms occasionally show up in adults as well.
You can also contract the flu and not exhibit any of these symptoms. Around 8% of people who test positive for the flu virus have no symptoms, according to the Centers for Disease Control and Prevention.
What are some complications of the flu?
People who get sick with the flu generally spend a few days to a couple of weeks feeling miserable. In most cases, the illness passes fairly quickly and patients bounce back to their former selves.
However, the flu can leave others more seriously ill. A bad bout of the flu can be life-threatening.
Complications associated with the flu include:
- Sinus and ear infections
- Pneumonia
- Severe dehydration
- Myocarditis, an inflammation of the heart
- Encephalitis, and inflammation of the brain
- Myositis, an inflammation of the muscle tissues
- Respiratory or kidney failure, or other types of multi-organ failure
- Sepsis, an extreme response of the body to an infection that can be life-threatening
Those most likely to experience such complications include adults who are 65 or older, children younger than 2, and people with other health conditions ranging from asthma and blood disorders to kidney and liver issues.
However, the flu can also cause severe sickness in younger, healthier people.
“Even young, otherwise healthy adults can become quite sick, and occasionally develop complications that land them in the hospital,” Mandal says.
During the most recent flu season of late 2024 to early 2025, somewhere between 27,000 and 130,000 people died due to the flu, according to the CDC.
The estimated range is wide because influenza surveillance does not capture all cases of the flu in the U.S., according to the CDC.
Flu prevention: what can you do?
There are several steps you can take to reduce your risk of becoming severely ill with the flu.
“The most effective protection against the flu remains the annual flu shot,” Mandal says.
Influenza viruses mutate constantly, which is why the flu vaccine is updated each year.
“While it’s not perfect, it significantly reduces the risk of severe illness, hospitalization and complications,” Mandal says.
Vaccination also helps reduce spread of the flu in the community, protecting those who are most vulnerable, she says.
Good hand hygiene “matters more than people realize,” Mandal says. Frequent handwashing — or using alcohol-based sanitizer when soap and water aren’t available —helps reduce transmission, she adds.
“Just as important is avoiding touching your face, since the virus can enter through the eyes, nose or mouth,” Mandal says.
Here are additional tips for reducing the odds of becoming sick, or spreading the flu to others once you have become infected:
- Regularly disinfect commonly touched surfaces, such as phones, keyboards and doorknobs
- Stay at home when you’re sick
- Cover coughs and sneezes properly
- Maintain healthy habits that support immune function, such as getting adequate sleep, eating foods that meet nutrition needs and engaging in regular physical activity
Taking precautions when you are sick helps protect your family, co-workers and the broader community, Mandal says.
“While mild symptoms can be tempting to brush off, even mild cases are contagious,” Mandal says.
When to seek medical care
Even if you take all of the standard precautionary steps, it does not guarantee you will not get the flu.
Although most people can recover from the flu at home, specific symptoms warrant prompt medical attention.
Mandal says that for adults, these include difficulty breathing, chest pain or pressure, or persistent high fever that doesn’t improve with medication
Severe weakness, confusion or signs of dehydration such as dizziness or very low urine output also warrant a trip to the doctor. Bluish lips or face are an emergency warning sign, Mandal says.
For children, red flags include fast or labored breathing, unusual drowsiness and inability to interact, extreme irritability or fever accompanied by a rash.
Anyone with chronic medical conditions who notices those conditions worsening should also seek care, Mandal says.
Antiviral drugs can be prescribed to fight the flu. These are available in pill, liquid, inhaled powder or intravenous solution form.
“Timing matters when it comes to treatment,” she says. “Antiviral medications can shorten the duration and reduce the severity of influenza if started early, particularly for people at higher risk.”
Some patients ask their doctor for antibiotics to treat the flu, but these drugs only work on bacterial infections, not viral infections such as the flu. So, you probably will not benefit from antibiotics unless you develop a secondary bacterial infection that causes pneumonia or another illness.
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