Table of ContentsView AllTable of ContentsSymptomsFlu vs. Cold vs. COVID-19CausesSpreadFlu SeasonComplications and RisksDiagnosisTreatmentDurationContagiousnessFlu ShotNext in Flu GuideUnderstanding the Different Types of Flu
Table of ContentsView All
View All
Table of Contents
Symptoms
Flu vs. Cold vs. COVID-19
Causes
Spread
Flu Season
Complications and Risks
Diagnosis
Treatment
Duration
Contagiousness
Flu Shot
Next in Flu Guide
Seasonal flu is highly contagious, often spreading before an infected person recognizes symptoms like a sore throat, cough, congestion, and body aches. Seeking antiviral flu treatment within a few days of symptoms can shorten your illness.
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Flu Symptoms
Flu symptoms can vary from person to person. For example, some people will develop a fever with the flu, while others will not. Your symptoms can be mild to severe, depending on your age, overall health, and the strain of the virus.
The most common flu symptoms include:
Digestive symptoms, like vomiting and diarrhea, are more likely to occur among children thanadults with the flu.
Warning Signs You Need Medical Care
These symptoms are warning signs that your respiratory infection needs immediate medical care:
The table below outlines the main differences between the flu, cold, and COVID-19 symptoms.
What Causes the Flu?
Flu A vs Flu B
Though there are four flu viruses—A, B, C, and D—but influenza A and B are the two primarily affecting people. Influenza C only causes mild infections in people, and influenza D primarily affects cattle. Only influenzas A and B are known to cause flu pandemics and regularly cause seasonal epidemics every winter.
Influenza A and B are treated the same way and can have similar symptoms, but they have somedifferencesin how they affect people.
Flu A is more common, responsible for approximately 75% of all flu cases experienced yearly.This is likely because itmutates(changes) quickly, allowing it to transfer from animals and birds to humans, and then between people. Frequent viral mutation also means that new vaccines are needed every year to keep up with new flu A strains.
Influenza A is the only type of flu that causes pandemics. It can affect adults and children but tends to be more severe in adults.
Flu B only affects humans and, more commonly, infects children. While it usually has mild symptoms, it can have more severe effects on kids under age 5.
How the Flu Spreads
The virus can also live for a time on surfaces. If one person sneezes or coughs the droplets may land on a surface. Or, a person with a flu infection may sneeze into their hand, and then touch an object. In both cases, the virus spreads to people who touch the area before the virus dies.
When Is Flu Season?
Flu season runs from October through May. However, cases typically peak between December and March, with the most illnesses frequently reported in February.
Though flu viruses circulate all year long,flu seasonoccurs in the fall and winter because of cooler temperatures. In colder months, the influenza viruses thrive longer, natural defenses are down, and transmission between people increases.
Most people will recover from the flu within a few days to two weeks.Unfortunately, some people develop flu complications, which can become life-threatening.
Flu often causes ear and sinus infections. Some people develop serious health complications, such aspneumonia(a lung infection), and heart inflammation (myocarditis).
Though rare, flu may also cause inflammation of the brain (encephalitis) or muscles (myositis).In some cases, a flu infection can lead to multi-organ failure or an extreme whole-body inflammatory response calledsepsis.
If you have a chronic health condition, the flu can make your symptoms worsen. For instance, the flu can lead to more severe asthma attacks among people who already have this respiratory condition.
Your risk of developing complications is higher if you:
How Is the Flu Diagnosed?
Your healthcare provider will ask about your symptoms and how long you’ve been sick. They’ll also look in your ears, nose, and throat and listen to your lungs with a stethoscope.
If flu activity is high in your area and your symptoms point to influenza, your healthcare provider may diagnose and treat you based on your physical assessment and after eliminating other reasons for your symptoms.
Your provider may also perform a flu test to determine if your symptoms are definitely due to the influenza virus. The flu test is especially useful when flu activity is low in your area but your healthcare provider still thinks you might have it.
An in-officerapid influenza testtakes about 15 minutes to get results.The test typically involves a nasal or throat swab to determine whether you have the flu virus.
Flu Treatment
If you become sick with the flu virus, there are some measures you can take to help speed up your recovery as you ride the illness out.
Antiviral medications may help reduce the duration of symptoms and prevent flu complications if you start taking them within the first few days of symptoms. Visit your healthcare provider as soon as symptoms begin to get a prescription.
Otherwise, the best thing for you to do if you have the flu is to stay home and rest. Avoid contact with others unless you require medical care. If you’re in a high-risk group or develop warning signs, seek medical attention immediately.
Try to stay isolated (away from other people) until you are fever-free and without other symptoms for 24 hours.If you need to be around others, wear a mask to help prevent the spread of germs.
Self-Care For Flu
How Long Does the Flu Last?
For most healthy people, symptoms of the flu go throughstages, subsiding within a few days to two weeks. For people who are in a high-risk group or have other existing medical conditions, the flu may take longer to heal.
How Long Is the Flu Contagious?
If you pick up the flu virus, you can give it to someone else one day before your symptoms begin and up to seven days after they improve. The most contagious period is the first three to four days after you start feeling sick.
Prevention
The most effective way to prevent flu is getting an annualflu shot. While the most prominent circulating flu virus strains change yearly, scientists do their best to predict which ones will be the most contagious using research. Annual vaccines are designed around these data.
Regardless, all flu vaccines in the United States protect you against three different flu viruses. These include an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus.
A healthcare provider can answer any questions about theflu shotand determine which one is best for you, especially if you are over 65. Older individuals are at a higher risk for complications from the flu. They should receive a higher dose or an adjuvanted flu vaccine that contains an ingredient to produce a better immune response.
The best time to get your flu shot is in September or October, so your body has time to prepare antibodies before peak flu season arrives. Annual flu shots are available at many pharmacies, grocery stores, and primary care offices.
How Effective Are Flu Vaccines?The Centers for Disease Control and Prevention (CDC) conducts annual studies to determine how effective the flu vaccine is each year. The most recent data suggests a 40% to 60% lower risk of getting the flu among people who get their annual flu shot. One of the most significant factors in its effectiveness is how well-matched the vaccine is with the most prevalent virus strains each year.
How Effective Are Flu Vaccines?
The Centers for Disease Control and Prevention (CDC) conducts annual studies to determine how effective the flu vaccine is each year. The most recent data suggests a 40% to 60% lower risk of getting the flu among people who get their annual flu shot. One of the most significant factors in its effectiveness is how well-matched the vaccine is with the most prevalent virus strains each year.
Summary
The flu virus causes mild to severe symptoms that usually appear suddenly. The most common flu symptoms include fever, body aches, fatigue, sore throat, cough, headache, congestion, and a runny nose. Symptoms such as difficulty breathing, chest pain, confusion, and severe weakness are signs of a developing complication that needs immediate medical attention.
Your healthcare provider can prescribe antiviral medication to help you feel better faster. However, you must see your provider in the first few days after your symptoms appear. Other than antiviral medication, the only flu treatment is self-care. You should rest, drink plenty of fluids, and take over-the-counter medications to relieve symptoms.
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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.Centers for Disease Control and Prevention.Signs and Symptoms of Flu.Centers for Disease Control.Types of influenza viruses.Bhat YR.Influenza B infections in children: A review.World J Clin Pediatr. 2020;9(3):44-52. Published 2020 Nov 19. doi:10.5409/wjcp.v9.i3.44Centers for Disease Control.How the flu spreads.Centers for Disease Control.Flu season.Centers for Disease Control.Flu symptoms & complications.National Library of Medicine: MedlinePlus.Flu (influenza) test.Centers for Disease Control and Prevention.Treatment of flu.Centers for Disease Control and Prevention:Flu: What to do if you get sick.Centers for Disease Control.Flu: What to do if you get sick.Cornell University.Self-care guide for influenza (flu).Johns Hopkins Medicine.A parent’s guide to the flu.Centers for Disease Control and Prevention.US Will Transition to Trivalent Flu Vaccines for 2024-2025.Centers for Disease Control.Flu & people 65 years and older.Centers for Disease Control and Prevention.Benefits of the flu vaccine.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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