Flu, also called influenza, is an infection of the nose, throat, and lungs, part of the respiratory system. A virus causes the flu. Influenza is commonly called the flu, but it’s different from the stomach “flu” viruses that cause diarrhea and vomiting.

Most people with the flu get better on their own.

But sometimes, influenza and its complications can be deadly. Some groups of people are at a higher than average risk of having flu complications, including:

Young children, especially those aged 12 months or younger.

✓ People who plan to be pregnant, are pregnant, or recently gave birth during flu season. Adults older than age 65.

People who live or work in facilities with many other residents. Examples are those in nursing homes, military barracks, and people in the hospital.

In the United States, some groups have a higher risk of needing hospital treatment for flu. Those people who are American Indian or Alaska Native, Black or Latino.

Although the annual influenza vaccine isn’t 100% effective, it lowers the chances of having severe complications from the flu. This is especially true for people at high risk for flu complications. Symptoms

At first, the flu may seem like a cold with a runny nose, sneezing, and sore throat. Colds usually start slowly. But the flu tends to come on quickly. And while a cold can be miserable, you usually feel much worse with the flu.

symptoms of the flu

Common symptoms of the flu often – but not always include fever as well as aching muscles, chills, and sweats. Other symptoms include:


Dry, persistent cough.

Shortness of breath.

Tiredness and weakness.

Runny or stuffy nose.

Sore throat.

Eye pain.

Vomiting and diarrhea also are flu symptoms. But they are more common in children than in adults. When to see a doctor

Most people who get the flu can treat themselves at home and often don’t need to see a healthcare professional. If you have flu symptoms and are at risk of complications, see your healthcare professional immediately. Taking antiviral medicine to treat the flu may shorten the length of your illness and help prevent more severe problems. If you have emergency flu symptoms, get medical care immediately. For adults, emergency symptoms can include: Difficulty breathing or shortness of breath.

Chest pain.

Ongoing dizziness.


Worsening of existing medical conditions.

Severe weakness or muscle pain.

Emergency symptoms in children include all the symptoms seen in adults, as well as:


Gray or blue lips or nail beds. Dehydration.

Viruses cause influenza. These viruses travel through the air in droplets when someone with the infection coughs, sneezes, or talks. You can inhale the droplets directly. Or you can pick up the germs from touching an object, such

as a computer keyboard, and then touching your eyes, nose, or mouth.

People with the virus are likely contagious from about a day before symptoms appear until about 5 to 7 days after they start. Children and people with weakened immune systems may be slightly more contagious.

Influenza viruses are constantly changing, with new strains appearing often. If you’ve had influenza in the past, your body has already made antibodies to fight that specific strain of the virus.

If future influenza viruses are like those you’ve come across before, either by having the disease or by getting vaccinated, those antibodies may prevent infection or lessen its severity.

However, antibody levels may decline over time. Antibodies against past influenza viruses may not protect you from new influenza strains. New strains can be very different from what you had before.

Risk factors

Factors that may raise your risk of getting the flu or its complications include:

Age. Seasonal influenza tends to have worse outcomes in young children, especially those age 12 months and more youthful. Adults older than age 65 also tend to have worse outcomes.

Living or working conditions. People who live or work in facilities with many other residents, such as nursing homes, are more likely to get the flu. People who are staying in the hospital also are at higher risk. Weakened immune system. Cancer treatments, anti-rejection medicines, long-term use of steroids, organ transplants, blood cancer, or HIV/AIDS can weaken the immune system. This can make it easier to catch the flu virus and may increase the risk of developing complications.

Chronic illnesses. Chronic conditions may increase the risk of influenza complications. Examples include asthma and other lung diseases, diabetes, heart disease, nervous system diseases, previous history of stroke, metabolic disorders, problems with the airway, and kidney, liver, or blood disease.

Race or ethnicity. In the United States, people who are American Indian or Alaska Native, Black, or have a higher risk of influenza complications.

Latino may

Aspirin use under age 20. People younger than 20 years of age and receiving long-term aspirin therapy are at risk of developing Reye’s syndrome if infected with the influenza virus.

Pregnancy. Pregnant people are more likely to develop influenza complications, particularly in the second and third trimesters. This risk continues up to two weeks after the baby is born.

Obesity. People with a body mass index (BMI) of 40 or higher have an increased risk of flu complications. Complications

If you’re young and healthy, the flu usually isn’t serious. Although you may feel awful while you have it, the flu usually goes away in a week or two with no lasting effects. But children and adults at high risk may develop complications that may include:

Pneumonia. Bronchitis.

Asthma flare-ups.

Heart problems.

Ear infections.

Acute respiratory distress syndrome.

Pneumonia is one of the most serious complications. For older adults and people with chronic illnesses, pneumonia can be deadly.


The U.S. Centers for Disease Control and Prevention (CDC) recommends annual flu vaccination for everyone age six months or older. The flu vaccine can lower your risk of getting the flu. The flu vaccine reduces your risk of

having severe illness from the flu and needing to stay in the hospital due to flu. The flu vaccine also lowers your risk of dying of flu.

Flu vaccination is essential because the flu and coronavirus disease 2019 (COVID-19) cause similar symptoms. Both COVID-19 and the flu may be spreading at the same time. Vaccination is the best way to protect against both. And if a COVID-19 vaccine or booster and a flu vaccination are due simultaneously, you can often get vaccinated

for both in one visit.

This year’s seasonal flu vaccines each protect against the four influenza viruses expected to be the most common during this flu season. This year, the vaccine will be available as an injection and a nasal spray. High-dose flu vaccines will also be offered for adults aged 65 and older.

The nasal spray is approved for people between the ages of 2 and 49. It isn’t recommended for some groups, such as: People who had a severe allergic reaction to a flu vaccine.

Pregnant people.

Children aged 17 years or younger taking aspirin or a salicylate-containing medicine.

People with weakened immune systems and caregivers or close contacts of people with weakened immune systems.

Children between ages 2 and 4 years old diagnosed with asthma or wheezing in the past 12 months.

People who recently took antiviral medicine for the flu.

People with a cerebrospinal fluid leak or the potential for a leak, as with a cochlear implant.

You can still get a flu vaccine if you have an egg allergy.