Flu Symptoms: Signs You Might Have the Influenza Virus

Flu symptoms like fever, chills, body aches, cough, and fatigue can help identify if you have influenza. Learn the signs to watch for and when to see a doctor.

The flu, or influenza, is a virus that infects your nose, throat, and lungs. 1 It comes on fast with symptoms like fever, chills, and body aches. You might also have a cough, feel tired, get headaches, or have a runny nose. Sometimes, you might even throw up. 1

Colds and the flu both make you feel bad, but the flu can be worse. It’s important to know the symptoms. This can help you or others get the right treatment fast. It’s especially crucial for older people, young kids, and those with ongoing health problems. 2,3,1

Key Takeaways

  • The flu is a viral infection that can cause fever, chills, body aches, cough, fatigue, and other symptoms.
  • Flu symptoms are often more severe than cold symptoms and come on more quickly.
  • Certain groups, such as the elderly, young children, and those with chronic conditions, are at higher risk for flu complications.
  • Recognizing flu symptoms is important for seeking proper medical treatment and preventing the spread of the virus.
  • Getting an annual flu vaccine is the best way to protect against the influenza virus.

Understanding the Flu Virus

Influenza viruses change a lot, with new types showing up regularly.2 If you’ve had the flu before, you might not be fully protected. The flu differs from a cold by how quickly symptoms hit and their severity. Flu shows up fast with high fever, severe body aches, and being very tired. Colds are slower, with lighter symptoms.

Flu vs. Common Cold

Though they share a few symptoms, the flu is usually worse than a cold. Flu shows up fast with fever, chills, body aches, and more. It can also make you feel really tired, give you a headache, and cause vomiting. Colds start slowly and are less severe, often just making your nose run or feel stuffy.

Influenza Strains and Mutation

Influenza viruses have different strains, marked by their outer proteins. Humans mainly deal with influenza A and B.4 These viruses can change a lot, which is why the flu shot gets updated every year. It focuses on the virus strains expected to be common that year.2

Influenza Type A has various subtypes, like H1N1 and H3N2.5 Types A and B are severe, while Type C is usually mild or unnoticed. The flu’s symptoms, its complications, and its constantly changing nature make it a big health problem.5

Influenza A mainly strikes in wintertime.4 Every winter brings different subtypes of this virus. In 2009, H1N1 broke out in a pandemic, affecting a lot of people, especially in Australia.4

Common Flu Symptoms

Fever and Chills

A fever is a key sign of having the flu. These fevers are often over 100°F (37.8°C). They can stick around for 3-4 days.2 When you have a fever, you might also feel chills and shiver. This is your body’s way of trying to get rid of the infection.

Body Aches and Fatigue

Feeling achy all over and very tired are common flu symptoms. The flu can make your muscles and body hurt a lot.2 You might feel too tired to do anything.

Respiratory Symptoms

A dry cough, sore throat, and being stuffed up are other signs. Sometimes, the cough can be really bad.

Flu Symptoms in Children

Children with the flu may have vomiting and diarrhea more than adults.6 Yet, not all kids with the flu get these stomach issues.6 Most kids feel sick in their chest and have body aches.

Vomiting and Diarrhea

6 The flu might make kids feel like they want to throw up or have an upset stomach. But, they usually get a very high fever and aching all over their bodies.6 They might also feel really tired.6

6 Kids who don’t get the flu shot are more likely to get sick.6 Especially those who are very young or have health problems. Getting medicine called antivirals early can make the sickness less severe.

Most children start to feel better from the flu in about a week.7 After that, they usually don’t have any more health issues.7 It’s important for kids over 6 months to get the flu shot. This helps them stay well and avoid serious problems from the flu.

flu symptoms in children

Flu symptoms

Flu symptoms include fever, chills, and body aches. You might feel tired and have a cough. Your throat could hurt, and your nose might run or feel stuffed up.2 Some people, especially kids, might also throw up or have diarrhea.3 The flu hits you fast and feels worse than a cold.

If you’re older than 65, the flu can be dangerous.2 People from certain racial backgrounds and those with a high BMI or certain diseases have more risk too.2 Cancer and HIV also make the flu more dangerous.2

Having a flu shot lowers the chances of getting very sick.2 It’s recommended for everyone over 6 months old.2 Wash your hands and keep things clean to stop the flu from spreading.2

Babies and seniors are at higher risk of serious flu.3 Living in crowded places like nursing homes also raises your risk.3 Diseases and certain medicines can make the flu hit harder.3

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Health conditions such as asthma make flu complications more likely.3 Some groups, like U.S. Native Americans and Latinos, are more at risk.3 Taking aspirin and getting the flu can lead to a rare but serious illness in young people.3

If you’re pregnant, the risk goes up.3 Obesity also makes the flu more dangerous.23 The flu can cause pneumonia and other severe illnesses.3

For adults, some signs of a life-threatening flu include very bad breathing and chest pain.3 Kids can show the same signs, plus look pale or dehydrated.3

Symptom Onset and Duration

Flu symptoms come suddenly; cold signs start slowly.2 When you get the flu, you might feel very sick right away. A cold usually shows up with a runny nose first. Then, a mild sore throat may get worse over a few days.

Flu vs. Cold Symptom Onset

Distinguishing between the flu and a cold starts with how the symptoms show up. Flu signs show up fast and can hit hard. Cold symptoms, on the other hand, take their time to fully develop.

How Long Do Flu Symptoms Last?

People with flu usually get better in a week or two, but feel tired for a bit longer.8 You might have fever and body aches for 3-4 days. Cough and being tired can last 1-2 weeks.8 Sometimes, flu leads to other serious issues.

Serious Flu Complications

Pneumonia is a serious flu complication that can be life-threatening. This is especially true for older adults, kids, and those with ongoing health issues.2 It can also cause acute respiratory distress syndrome, which is a severe type of breathing failure.2

The flu can make health issues like asthma or heart disease much worse. It puts a lot of stress on the body, which is tough for anyone with ongoing illnesses.2

Pneumonia and Respiratory Distress

If the flu leads to pneumonia, you might get a fever, chest pains, chills, and start coughing up green or bloody mucus.9 It can get so bad that you need to go to the hospital.9

Pneumonia symptoms can last for about 2 weeks. If you’re very young or old, or if you have a weak immune system, they might last even longer.9

Pneumonia can cause serious problems like trouble breathing, chest pains, and a fever over 102°F.10 There’s even a risk of fluid in your lungs, bacteria in your blood, and acute respiratory distress syndrome.10

Worsening of Chronic Conditions

The flu can really make ongoing health issues worse. For instance, it might cause asthma attacks in those who suffer from asthma. It could also make heart disease more severe.2 The stress of the flu on the body is bad news for anyone with a long-term illness.2

Chronic bronchitis is a type of irritation in your lungs that, if not treated, can lead to pneumonia, emphysema, heart failure, and more.10

If you end up with flu complications, it’s important to see a doctor early. Most of these problems get better with the right treatment.10

High-Risk Groups for Flu Complications

Some people have a higher chance of getting bad flu symptoms.11 This includes older adults, aged 65 and over, and kids under 2. They can get severe problems like pneumonia from the flu.11

Pregnant Women

Pregnant women, especially in the second and third trimesters, are more at risk too.2 Their immune and heart systems change during pregnancy. This makes them more likely to have problems from the flu.2

Chronic Health Conditions

If someone has asthma, diabetes, heart or kidney issues, or a weak immune system, the flu is more dangerous.112 Flu can make these health conditions worse. This can lead to more sickness and needing to go to the hospital.112

Is it Flu or COVID-19?

Both the flu and COVID-19 can make you feel sick with fever, cough, body aches, and tiredness. So, it’s hard to tell them apart just from these signs.12 But, COVID-19 might cause you to have trouble breathing or you might not taste or smell well. These are not common signs with the flu.12

Similarities and Differences

The flu and COVID-19 share a lot of the same symptoms. But, COVID-19 is more easily spread and can make you sicker than the flu.13 It often leads to more severe illness, especially in those without existing health problems. This can result in many more hospital visits and deaths.13

Both illnesses can cause pneumonia and other serious issues. However, COVID-19 has extra complications like blood clots or ongoing health problems. It can even affect children with a rare but serious condition called MIS-C.1312

Getting Tested

Testing is the best way to know if you have the flu or COVID-19. Doctors can do quick tests or send samples for more detailed lab checks.13

It’s very rare to have both the flu and COVID-19 at the same time.12 Children are less likely to get COVID-19, making up only about 1% to 2% of all cases worldwide.12

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If you feel sick with the flu or COVID-19 symptoms, don’t wait. Getting checked by a doctor and tested is very important. Early care can stop things from getting worse and keep these sicknesses from spreading. Plus, you’ll know the exact treatment you need.

When to Seek Medical Attention

Most people with the flu can recover at home. But, if you see emergency warning signs, get medical help fast.3 These signs include trouble breathing, chest pain, or if you suddenly feel dizzy. You should also get help if you have a chronic illness and notice it’s getting worse.3

Getting treated quickly with antiviral drugs can make the flu less severe. It can also stop you from getting other health issues.3

Emergency Warning Signs

For adults, the flu’s emergency signs are hard to breathe, chest pain, seizures, and extreme weakness.3 Kids might have trouble breathing, seem very thirsty, or show blue areas in their lips or nails.3 Everyone with severe flu symptoms should see a doctor right away.

Even though most flu cases are mild, not everyone will get better at home.3 People at high risk or with severe symptoms might get antiviral drugs, like oseltamivir (Tamiflu). This helps avoid serious complications.3

Preventing the Flu

To fight the flu, get your flu shot every year.14 The vaccine changes to match the flu types that experts think will be common. It’s not perfect, but it lowers your chances of getting really sick from the flu.15

Annual Flu Vaccination

Everyone over 6 months should have a flu shot each year.15 The shot is the best way to beat the flu. It teaches your body how to fight this year’s most common flu types.14

Good Hygiene Practices

Aside from the vaccine, clean habits are key to avoiding the flu. This means washing your hands a lot, covering your mouth and nose when you cough or sneeze, and not touching your face.14 The virus can get on your hands by touching things where it’s hiding. It can survive outside the body for a while, up to two days.15 So, make sure to clean things you touch often to help stop germs from spreading.14

You can spread the flu right before you feel sick and even a few days after.15 But, you’re most likely to give it to others in the first 5 days after you feel sick and 48 hours after your fever is gone.15 When sick, stay home until you’re 24 hours without a fever and you’re feeling better.14 Wearing a mask helps prevent spreading the flu if you have it.14

Washing your hands or using hand sanitizer often is a great defense.14 Germs move from your hands to your face easily.14 In shared spaces, cleaning is very important to get rid of these germs.14 Always have plenty of clean supplies like tissues and soap available.14 You can also put up posters and hand out flyers to help people remember to protect themselves.14

Treating Flu Symptoms

You can manage many flu symptoms with over-the-counter drugs. These include acetaminophen, ibuprofen, or decongestants. They help lower fever, soothe aches, and clear up congestion.16 It’s vital to drink a lot of fluids and rest well for a full recovery.

Over-the-Counter Remedies

Non-prescription drugs are great for easing common flu symptoms. Acetaminophen and ibuprofen reduce fever and body pains. Decongestants help unblock your nose and sinuses.16 Always read and follow the medicine label’s instructions. Don’t take more than the label suggests.

Antiviral Medications

If you are at high risk for flu complications, your doctor might prescribe antiviral drugs. Some include oseltamivir (Tamiflu) or zanamivir (Relenza).16 These meds can lessen how long you’re sick and how bad you feel. If you take them within the first 48 hours of getting sick, they work best.17

Antiviral drugs make the flu milder and shorten its duration. They can also help prevent serious issues like pneumonia, but you need to start treatment early.17

Remember, antibiotics don’t work against flu viruses. They won’t speed up your recovery.17 Plus, antibiotics can have bad side effects. These include simple problems like rashes or more severe issues like getting infections that are hard to treat.17

Flu Transmission and Contagiousness

The flu virus spreads mostly when someone who has it coughs, sneezes, or talks.18 You can also get the flu by touching things with the virus on them.18 Sick people can spread the flu a day before showing symptoms and for 5-7 days after.19 But, kids and those with weak immune systems might spread it for even longer.19

In the U.S., the flu season begins in fall and lasts through spring.19 The flu can be passed on 1 day before symptoms show and up to 5-7 days later. Sometimes, it’s contagious even longer.19 Being in large groups, especially on cruises, can up your risk of catching the flu.19

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The New York State Department of Health and the CDC watch for flu outbreaks. They keep us updated on flu’s spread.19 It’s key to know how the flu spreads to prevent it and keep it from spreading. This helps stop this serious sickness from spreading.


Finding out the common signs of the flu is key. Symptoms include fever, chills, body aches, and cough. Knowing them helps get the right medical help and stop the virus from spreading.20

Most healthy people get better from the flu in 1-2 weeks. But, the flu can be very serious for some, even life-threatening. This is often the case for those at high risk.20 To avoid getting sick, getting the flu shot every year and keeping your hands clean are important. So is covering your mouth when you cough or sneeze.21

Flu outbreaks can be very dangerous. They can lead to many deaths worldwide, especially if new flu types appear from animals.20 Taking medicine like oseltamivir (Tamiflu) early can help make your flu weaker and shorter. But, it needs to be in the first 48 hours.20 Bird flu, like H5N1 and H7N9, can be very harmful, particularly in Asia.20

Knowing about the flu helps you protect yourself and your neighbors.2021 Being well-informed and acting early can really help. It can lessen how bad the flu affects everyone.20


What are the common symptoms of the flu?

Common flu symptoms are fever, body aches, and fatigue. You might also have a cough, sore throat, or a runny nose. Headaches, vomiting, and diarrhea can happen too, mostly in kids.

How do flu symptoms differ from cold symptoms?

Flu symptoms hit quick, making you feel really sick fast. Cold symptoms sneak up more slowly over a few days. A cold starts mild, like with a runny nose, but then gets worse.

What are the different strains of influenza viruses?

Influenza viruses have different strains, marked by their surface proteins. The main ones causing human epidemics are influenza A and B.

What are the most common flu symptoms in children?

Kids with the flu may have vomiting or diarrhea more than adults. But, not all kids get stomach symptoms. Most have coughs and body aches like adults do.

How quickly do flu symptoms come on?

Flu symptoms appear fast, usually out of the blue. Colds take their time to make you feel sick. The flu makes you feel bad right away, but a cold starts mild and gets worse slowly.

How long do flu symptoms last?

The flu lasts about 1-2 weeks but you might feel better after one. The worst parts, like fever and aches, last 3-4 days. Coughs and being tired can stick around for 1-2 weeks more.

What are some serious complications of the flu?

Pneumonia is a big danger with the flu, especially for the very young or old and people with health problems. It can also cause a hard-to-breathe condition called acute respiratory distress syndrome.

Who is at higher risk of developing serious flu complications?

Older adults and young children have a higher risk of dangerous flu complications, like pneumonia. So do pregnant women in their second or third trimester and people with specific medical conditions.

How can I tell if I have the flu or COVID-19?

The flu and COVID-19 have similar symptoms but some things like shortness of breath and loss of taste aren’t common with the flu. The only sure way to tell what you have is through testing.

When should I seek medical care for the flu?

You can often get better from the flu at home. But, if you have trouble breathing, chest pain, dizziness, or your health problems get worse, seek help right away.

How can I prevent getting the flu?

The best defense against the flu is getting a flu shot every year. Also, wash your hands often, cover your mouth when you cough or sneeze, and try not to touch your face.

How can I treat flu symptoms?

Over-the-counter drugs like acetaminophen and ibuprofen can help with fever and aches. If you’re at high risk, your doctor might prescribe antiviral drugs to lessen symptoms.

How long is the flu virus contagious?

You can spread the flu from about a day before feeling sick until about 5-7 days after. Some, like kids and those with weak immune systems, may spread it longer.

Source Links

  1. https://www.medlineplus.gov/flu.html
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  3. https://www.mayoclinic.org/diseases-conditions/flu/expert-answers/flu-symptoms/faq-20057983
  4. https://www.healthdirect.gov.au/influenza-a-flu
  5. https://www.lung.org/lung-health-diseases/lung-disease-lookup/influenza/learn-about-influenza
  6. https://www.hopkinsmedicine.org/health/conditions-and-diseases/influenza/influenza-flu-in-children
  7. https://www.healthychildren.org/English/health-issues/conditions/flu/Pages/the-flu-what-parents-need-to-know.aspx
  8. https://www.cdc.gov/flu/professionals/acip/clinical.htm
  9. https://www.webmd.com/cold-and-flu/flu-complications
  10. https://www.healthline.com/health/flu-complications
  11. https://www.marshfieldclinic.org/specialties/primary-care/flu/flu-high-risk
  12. https://www.nyp.org/medicalgroups/queens/for-patients/healthcare-articles/covid-19-vs-flu
  13. https://www.mayoclinic.org/diseases-conditions/coronavirus/in-depth/coronavirus-vs-flu/art-20490339
  14. https://www.cdc.gov/flu/prevent/actions-prevent-flu.htm
  15. https://www.prevention.va.gov/flu/prevention/index.asp
  16. https://www.mayoclinic.org/diseases-conditions/flu/diagnosis-treatment/drc-20351725
  17. https://www.cdc.gov/flu/treatment/treatment.htm
  18. https://www.cdc.gov/flu/about/keyfacts.htm
  19. https://www.health.ny.gov/diseases/communicable/influenza/fact_sheet.htm
  20. https://www.uptodate.com/contents/influenza-symptoms-and-treatment-beyond-the-basics/print
  21. https://www.healthdirect.gov.au/flu