Influenza: Symptoms, Treatment, Prevention & Care

Introduction

Influenza is often called the flu. It is a contagious illness caused by influenza viruses [3,5]. These viruses infect the nose, throat, and sometimes the lungs [3,5].

Flu can range from mild to severe [3]. In some cases, it can cause life-threatening problems [3]. Certain people have a higher risk of serious illness [1,2].

Knowing influenza symptoms, treatment, prevention, and when to seek care can help you make safer choices. Most people recover at home without medical care [1]. However, some people need prompt treatment or emergency help [1].

This guide covers common flu symptoms and home care. It also explains antiviral drugs, flu prevention, and urgent warning signs.

Overview: What Influenza Is and How It Spreads

Influenza viruses and respiratory illness

Influenza is a respiratory illness caused by influenza viruses [3,5]. The viruses affect tissues in the nose and throat [5]. They can also infect the lungs [5].

The illness affects each person in a different way. Some people have mild flu symptoms [3]. Others become very sick or develop serious problems [3].

Young children have a higher risk of severe flu [1,2]. Adults age 65 and older also face greater risk [1,2]. Pregnancy and some long-term health problems can raise the risk as well [1,2,4].

Flu often spreads through a community during seasonal outbreaks [9]. Many people may become sick around the same time [9].

How flu differs from a cold or COVID-19

Flu, colds, and COVID-19 can cause similar symptoms [8,9]. Flu often starts quickly, while a cold tends to develop slowly [8,10]. People also tend to feel worse with flu than with a cold [8,9].

Different viruses cause the flu and the common cold [9]. However, symptoms alone may not separate flu from COVID-19 [9]. Testing may be needed to tell which illness is present [7,9].

A clinician may suggest a flu test to guide your care [7]. Testing may also help show if you could spread flu to others [7]. Some people age 2 and older may have access to home tests [7].

Tell your healthcare team if you use a home test [7]. You may need another test to confirm the result [7]. Treatment for a high-risk person should not always wait for a positive result [6].

Causes and How Flu Spreads Between People

An influenza virus causes the flu [3,5]. Influenza spreads easily from one person to another [2].

People with flu release respiratory particles when they cough, sneeze, or talk [5]. These particles can spread the virus to nearby people [5]. Close contact can make spread more likely [2,5].

Staying away from other people while sick helps limit contact [1]. People with flu should usually stay home except when they need medical care [1].

Handwashing may also help prevent infection [8]. Covering coughs and sneezes is another useful step [8]. Cleaning shared surfaces and improving airflow may further reduce spread [8].

Symptoms and Possible Complications

Early and common flu symptoms

Influenza symptoms usually begin suddenly [3]. Common flu symptoms include:

• Fever or feeling feverish [2,3]
• Chills [2,3]
• Cough [2,3]
• Sore throat [2,3]
• A runny or stuffy nose [2,3]
• Muscle or body aches [2,3]
• Headache [2,3]
• Tiredness or fatigue [2,3]

Not every person with influenza has a fever [2,3]. A lack of fever does not rule out the flu [2,3]. The illness can still be serious without fever [3].

Many people feel sick within two or three days after contact with the virus [2,8]. However, the timing can vary [2]. The quick start of aches and fatigue may suggest flu instead of a cold [8,10].

Symptoms in children and adults

Adults and children often have many of the same flu symptoms [2,3]. Both groups may have fever, cough, chills, aches, and fatigue [2,3]. Headache, sore throat, and congestion are also common [2,3].

Vomiting and diarrhea can occur with influenza [2,3,10]. These symptoms are more common in children than in adults [2,3,10]. Children may also have a higher fever than adults [2].

Flu does not look the same in every person [3]. One family member may have different symptoms from another. A person does not need every listed symptom to have influenza [3].

Testing may help when the cause is not clear [7]. It can also help when the result may change the care plan [7].

How long influenza lasts

Most people recover within a few days to less than two weeks [3]. Fever often improves before other symptoms fully go away [2]. Cough and low energy may last longer than the fever [2].

Recovery time can differ from one person to another. People should watch for new or worse symptoms during recovery.

Symptoms may improve and then return or become worse [1]. This pattern can be an emergency warning sign [1]. It needs prompt medical review [1].

Possible complications of influenza

Influenza can cause pneumonia [3]. Pneumonia is an infection that affects the lungs. It can become serious and needs medical care.

Flu can also make a long-term medical problem worse [3]. People with existing health problems face a greater risk of severe illness [2,9].

Flu complications can sometimes be fatal [3,8]. High-risk people should contact a healthcare professional early [1,4]. They should not wait for the illness to become severe [1,4].

Treatment and Recovery at Home

Rest, fluids, and symptom relief

Most people with mild flu do not need medical care [1]. Many also do not need prescription antiviral medicine [1]. They can often recover at home while watching their symptoms [1].

Rest can support recovery. Drink enough fluids to lower the risk of dehydration. Dehydration means the body does not have enough water.

Get medical advice if you cannot drink or keep fluids down. Severe dehydration can be an emergency warning sign [1].

Over-the-counter medicines may help with fever, headache, or body aches. Follow the product label. Ask a pharmacist or clinician if a product is safe for you.

This step is important if you take other medicines. It also matters if you have a long-term health problem.

Check the ingredients before combining cold or flu products. Many products contain more than one drug. A pharmacist can help you avoid taking the same ingredient twice.

Stay home while you are sick [1]. Avoid close contact with other people unless you need medical care [1]. This helps reduce the chance of spreading flu [1].

Prescription antiviral medicines

Flu antivirals are prescription drugs that fight influenza viruses [4]. They are not sold over the counter [4]. A healthcare professional must prescribe them [4].

Antivirals come in several forms [4]. These include pills, liquids, inhaled powder, and medicine given through a vein [4].

Prescription antivirals can ease symptoms and shorten the illness [4]. They work best when started within one or two days after symptoms begin [4]. Contact a clinician early if you may need treatment [4].

Later treatment may still help some hospitalized or very sick patients [6]. A clinician should start treatment quickly for high-risk patients with suspected flu [4,6].

A high-risk patient may not need to wait for a test result [6]. Treatment can begin when influenza is the likely cause [6]. This is sometimes called empiric treatment.

Examples of flu antivirals include oseltamivir and baloxavir [6,7]. Other examples include zanamivir and peramivir [6]. Each drug has approved age groups and safety limits [6].

A clinician chooses the best option for each patient [6]. Some health issues may make a drug unsafe. Do not take medicine prescribed for another person.

Who may need early treatment

People at higher risk should contact a healthcare professional early [1,4]. They may need prompt antiviral treatment [4,6].

Higher-risk groups include:

• Young children [1,2]
• Adults age 65 and older [1,2]
• Pregnant people [1,4]
• People who were recently pregnant [1]
• People with asthma or long-term lung disease [4]
• People with diabetes [4]
• People with heart disease [4]
• People with some other long-term medical problems [1,2]

A person who is very sick should also call a clinician [1]. The same advice applies if the person is worried about the illness [1].

A healthcare professional can decide if testing is needed [7]. The clinician can also decide if an exam or antiviral drug is needed [4,7].

Medicines and practices to avoid

Antibiotics treat bacterial infections. They do not treat influenza viruses. They are only useful when a bacterial infection is also present.

A healthcare professional should decide if antibiotics are needed. Do not take old antibiotics. Do not use medicine prescribed for someone else.

Children and teenagers should not take aspirin during a suspected viral illness. Aspirin use in this setting is linked to Reye syndrome. This rare illness can harm the brain and liver.

Only give aspirin if a clinician directs you to do so. Ask which pain or fever medicine is safe for the child.

Do not use someone else’s antiviral prescription. Flu antiviral medicines require a prescription from a healthcare professional [4].

When to See a Doctor

Who should contact a clinician early

Call a healthcare professional early if a high-risk person may have flu [1,4]. Early contact matters because antivirals work best within one or two days [4].

Do not wait if you are very sick or worried [1]. A clinician may start treatment before a flu test confirms the illness [6]. This can be important for high-risk or very ill patients [6].

Tell the clinician about any risk factors. These may include age, pregnancy, asthma, diabetes, or heart disease [1,4]. This information can help guide treatment.

High-risk people should not assume mild symptoms will stay mild. Prompt care may lower the risk of a delay in treatment [4,6].

Flu emergency warning signs in adults

Adults need immediate medical help for possible emergency warning signs [1]. These signs may include:

• Severe trouble breathing [1]
• Shortness of breath [1]
• Ongoing chest pain or pressure [1]
• New confusion [1]
• Seizures [1]
• An inability to wake or stay awake [1]
• Severe weakness [1]
• Severe dehydration [1]
• Symptoms that improve and then return or worsen [1]

Do not wait for a routine visit if these signs appear. Follow local emergency guidance. Call emergency services when needed.

Flu emergency warning signs in children

Children need urgent care for signs of severe breathing problems [1]. They also need help for dehydration or poor response [1].

Emergency warning signs may include:

• Fast or difficult breathing [1]
• Bluish lips or face [1]
• Seizures [1]
• Trouble waking or poor response [1]
• Severe muscle pain [1]
• Signs of dehydration [1]
• Fever or cough that improves and then worsens [1]

A child with severe or fast-changing symptoms needs prompt medical help. Follow your local emergency instructions.

Any fever in a baby younger than 12 weeks needs prompt medical review. Do not give a young baby fever medicine without medical advice.

The warning signs above are not a full list. Seek immediate help if a person seems very ill. You should also act quickly if symptoms get worse fast.

Prevention: How to Prevent Influenza and Protect Others

Annual influenza vaccination

A yearly flu vaccine is the main way to prevent influenza. Vaccination lowers the risk of getting flu [5]. It also lowers the risk of serious flu problems [5,8].

Flu vaccines are updated each year [5]. A vaccine may not prevent every case [8]. However, it can lower the chance of severe complications [8].

This protection is important for people at high risk [8]. Ask a doctor or pharmacist about current vaccine advice.

Everyday infection-control habits

Daily habits can help limit the spread of respiratory viruses [8]. Helpful steps include:

• Wash your hands often [8].
• Cover coughs and sneezes [8].
• Keep indoor air moving when possible [8].
• Clean and disinfect often-touched surfaces [8].
• Avoid close contact with sick people [1,8].

These steps can support flu prevention [8]. They do not replace the yearly vaccine. Vaccination remains a key way to prevent flu and serious complications [5].

Staying home and limiting spread

People with flu symptoms should usually stay home [1]. They should avoid contact with other people [1]. They may leave home when they need medical care [1].

Limiting close contact can help protect others. This is vital around people at high risk of serious flu.

Cover coughs and sneezes. Wash your hands after touching used tissues. Clean often-touched surfaces and improve airflow in shared rooms [8].

Follow current public health advice before returning to work or school. Guidance may change over time. A healthcare professional can give added advice when needed.

Conclusion

Knowing influenza symptoms, treatment, prevention, and when to seek care can support safer choices. Most people recover within a few days to less than two weeks [1,3]. Many people can recover at home [1].

Rest, fluids, and careful symptom checks can support home care. Staying home also helps limit contact with others [1].

High-risk people should contact a healthcare professional early [1,4,6]. They may need prompt antiviral treatment [4,6]. Antivirals work best when started within one or two days [4].

Later antiviral treatment may help hospitalized or very sick patients [6]. Treatment for these patients should not always wait for a positive flu test [6].

Yearly vaccination lowers the risk of flu and serious complications [5,8]. Handwashing, clean surfaces, and better airflow can add protection [8].

Seek immediate care for trouble breathing or ongoing chest pain [1]. Confusion, seizures, severe dehydration, and sudden worsening also need urgent attention [1]. Any fever in a baby younger than 12 weeks needs prompt medical review.