Most people who have the flu get better on their own. But sometimes this illness and its complications can be fatal. To protect against seasonal influenza, you can get the annual flu vaccine. Although the vaccine is not 100% effective, it reduces the chances of serious complications from the infection. This is important for people at high risk of flu complications.
In addition to the flu vaccine, you can take other steps to prevent flu infection. You can clean and disinfect surfaces, wash your hands, and keep the air around you moving.
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Symptoms
The viruses that cause influenza spread at high levels during certain times of the year in both the Northern and Southern Hemispheres. These are called flu seasons. In North America, flu season typically occurs between October and May.
Flu symptoms, such as a sore throat and a stuffy or runny nose, are common. You may also experience these symptoms with other illnesses, such as a cold. But colds usually start slowly, and the flu usually comes on quickly, two or three days after coming into contact with the virus. And while a cold can be annoying, you usually feel much worse with the flu.
Other common flu symptoms include:
- Fever
- Cough
- Headache
- Muscle aches
- Feel very tired
- Sweating and chills
In children, these symptoms may manifest more generally as restlessness or irritability. Children are also more likely than adults to experience earache, stomach upset, vomiting, or diarrhea with the flu.
In some cases, people experience eye pain, watery eyes, or notice that light hurts their eyes.
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When you should consult a doctor
Most people with the flu can treat it at home and often do not need to see a healthcare professional.
If you have flu symptoms and are at risk for complications, see a healthcare professional immediately. Taking antiviral medications within two days of the onset of symptoms can reduce the duration of the illness and prevent more serious problems.
If you have flu symptoms that indicate an emergency, seek medical attention immediately. In adults, symptoms that indicate an emergency may include the following:
- Difficulty breathing or shortness of breath.
- Chest pain or pressure.
- Constant dizziness.
- Difficulty waking up or confusion.
- Dehydration.
- Seizures.
- Worsening of pre-existing conditions.
- Great weakness or intense muscle pain.
In children, symptoms indicating an emergency include all of the symptoms seen in adults, plus the following:
- Rapid breathing or ribs that sink with each breath.
- Bluish or grayish lips or nail beds.
- Lack of tears when crying or dry mouth, as well as the lack of need to urinate.
- Symptoms, such as fever or cough, that improve, but then return or worsen.
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Causes
The flu is caused by viruses. These viruses travel through the air in droplets when someone with the infection coughs, sneezes, or talks. You can inhale the droplets directly. You can also come into contact with the viruses through an object, such as a computer keyboard, and then transfer them to your eyes, nose, or mouth.
It’s possible to spread the virus to others from approximately the day before symptoms appear until five to seven days after they begin. This is called being a contagious carrier. Children and people with weakened immune systems may be contagious for a slightly longer period.
Influenza viruses are constantly changing and new strains often appear.
A person’s first flu infection provides some long-term protection against similar flu strains. But the vaccines offered each year are made to match the flu virus strains most likely to spread that season. The protection these vaccines offer lasts for months in most people.
Risk factors
There are several factors that can increase your risk of contracting the flu virus or experiencing complications from a flu infection.
Older and younger age
Seasonal influenza tends to have worse outcomes in young children, particularly those under 2 years of age. Adults over 65 also tend to have worse outcomes.
Living conditions
People who live in facilities with many other residents, such as nursing homes and convalescent homes, are more likely to get the flu.
Weakened immune system
An immune system that doesn’t quickly clear the flu virus can increase the risk of getting the flu or suffering from flu-related complications. People may have a weakened immune system response from birth, due to an illness, or due to treatment for an illness or medication.
Chronic diseases
Chronic conditions can increase the risk of flu-related complications. Some examples include asthma and other lung diseases, diabetes, heart and nervous system diseases, a history of stroke, metabolic disorders, respiratory problems, and kidney, liver, or blood diseases.
Race or ethnic group
In the United States, American Indians, Alaska Natives, Black people, and Latinos may be at higher risk of requiring hospitalization for medical care due to the flu.
Aspirin treatment
Young people on long-term aspirin therapy are at risk of developing Reye’s syndrome if they become infected with the flu virus.
Pregnancy
Pregnant women are more likely to experience complications from the flu, particularly in the second and third trimesters.
Obesity
People with a body mass index (BMI) of 40 or higher are at higher risk for complications from the flu.
Complications
If you’re young and healthy, the flu is usually not serious. Although you may feel very ill while you have it, the flu usually goes away in a week or two with no lasting effects.
But high-risk people can develop other health problems after the flu, which are known as complications.
Contracting another infection can be a complication of the flu. This includes illnesses such as croup and sinus or ear infections. Lung infections are another complication. Infection of the heart muscle or the lining of the heart can occur after contracting the flu. And in some cases, people may experience a central nervous system infection.
Other complications may include:
- Acute respiratory distress syndrome.
- Muscle damage, known as rhabdomyolysis, or muscle swelling, known as myositis.
- Toxic shock syndrome.
- Worsening of a chronic illness, such as asthma or kidney disease.
Prevention
The U.S. Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months of age and older who does not have a medical reason to avoid vaccination receive an annual flu vaccine.
Getting the flu vaccine reduces the following:
- The risk of contracting the flu. If the vaccine is given late in pregnancy, it also helps protect the newborn from the flu.
- The risk of severe illness from the flu and the need for hospitalization.
- The risk of death from the flu.
Seasonal influenza vaccines for 2024-2025 provide protection against the three flu viruses expected to be most prevalent this season.
The vaccine is available as an injection, a jet injection device, and a nasal spray.
For older children and adults, the flu vaccine is usually given in an arm muscle. Younger children can receive the flu vaccine in a thigh muscle.
If you are an adult under 65, you can choose to receive the vaccine using a jet injection device. This device uses a fine, high-pressure jet of liquid to pass through the skin instead of a needle.
The nasal spray is approved for use by people ages 2 to 49. It is not recommended for some groups, including:
- People who have had a severe allergic reaction to the flu vaccine in the past.
- Pregnant women.
- Young people taking aspirin or a medicine containing salicylate.
- People with weakened immune systems and caregivers or close contacts of people with weakened immune systems.
- Children aged 2 to 4 years who have been diagnosed with asthma or wheezing within the last 12 months.
- People who recently received an antiviral medication for the flu.
- People with a cerebrospinal fluid leak or the possibility of a leak, such as occurs with a cochlear implant.
Talk to your healthcare team to find out if you should take any precautions with the nasal spray flu vaccine.
Vaccines known as high-dose or adjuvanted flu vaccines are also available. These vaccines can help some people avoid the need for hospital care due to the flu. People 65 and older are eligible to receive them. These vaccines are also recommended for people 18 and older who have received a solid organ transplant and are taking medications to weaken their immune response.
You can get the flu vaccine if you have an egg allergy.
The first time children ages 6 months to 8 years receive the flu vaccine, they may need two doses spaced at least four weeks apart. They can then receive the single annual dose of this vaccine. Consult your child’s healthcare professional.
Also, consult with your healthcare team before receiving the flu vaccine if you have previously had a severe reaction to this type of vaccine. People who have had Guillain-Barré syndrome should also consult a healthcare professional before receiving the flu vaccine. And if you don’t feel well when you get vaccinated, consult with your healthcare team about postponing the vaccination.
Control the spread of contagion
The flu vaccine is not 100% effective. Therefore, it’s important to take steps to reduce the risk of spreading the infection, including the following:
- Wash your hands. Wash your hands thoroughly and frequently with soap and water for at least 20 seconds. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol. Make sure friends and family you spend time with frequently, especially children, know the importance of handwashing.
- Avoid touching your face. Keeping your hands away from your eyes, nose, and mouth helps keep germs away from those areas.
- Cover your mouth when coughing and sneezing. Cough or sneeze into a tissue or your elbow. Then wash your hands.
- Clean surfaces. Regularly clean frequently touched surfaces to prevent the spread of infection by touching a surface with the virus on it and then your face.
- Avoid crowds. The flu spreads easily in crowded places, such as childcare centers, schools, office buildings, auditoriums, and public transportation. By avoiding crowds during peak flu season, you reduce your chances of becoming infected.
Avoid contact with anyone who is sick.
If you’re sick, stay home until you feel better and have been fever-free for 24 hours, and haven’t taken fever-reducing medication during that time. If your fever returns or starts to feel worse, stay away from others until your symptoms improve and you’ve been fever-free and fever-free for 24 hours. By doing so, you’ll reduce your chances of infecting others.
