What counts as influenza symptoms

TL;DR:

Flu starts fast with fever, cough, aches, and deep fatigue.
Not everyone gets a fever, but most feel worse than with a cold.
Watch for trouble breathing, chest pain, confusion, or dehydration.
Kids, older adults, pregnant people, and some conditions face higher risk.
Rest, fluids, and timely antivirals help. Seek urgent care for red flags.

Influenza is a viral illness that hits the nose, throat, and lungs. Symptoms usually start suddenly, often within two days after exposure. Many people describe the first day as being “hit by a truck.” You feel fine, then sick, in hours.

Typical flu symptoms include:

Fever or chills.
Dry cough.
Sore throat.
Runny or stuffy nose.
Muscle and body aches.
Headache.
Marked fatigue.

Some people also have vomiting or diarrhea. That happens more in children than in adults. Not everyone will have every symptom. Fever can be absent, especially in older adults.

In healthy people, most symptoms improve in three to seven days. Cough and tiredness can linger for two weeks or more.

Flu vs cold vs COVID

These illnesses can look alike. The speed and severity help you tell them apart. Flu tends to come on fast and makes you feel worse than a common cold. Colds build slowly and stay milder. COVID can overlap with both and may include loss of taste or smell, but that is less common now than in early waves. Testing is the only way to be sure.

Quick comparison

Feature	Flu	Cold	COVID
Onset	Sudden, within hours	Gradual	Varies
Fever	Common, not always	Rare	Common
Aches	Common, can be strong	Mild	Common
Fatigue	Common, can be heavy	Mild	Common
Cough	Common, dry	Common, mild to moderate	Common
Sore throat	Common	Common	Common
Runny nose	Common	Common	Common
Loss of taste/smell	Uncommon	Uncommon	Possible
Test to confirm	Flu test	Not needed	COVID test

[Related: How to tell flu from COVID at home → /guides/flu-vs-covid]

Red flags that mean urgent care

Call emergency services or go to urgent care right away if you or someone you care for has:

Trouble breathing or shortness of breath.
Chest pain or pressure.
New confusion, hard to wake, or fainting.
Lips or face turning blue or gray.
Severe weakness, dehydration, or no urination for 8 hours.
Seizures.
Worsening fever after initial improvement.

In children, also watch for:

Fast or labored breathing, ribs pulling in.
Refusing fluids or no tears when crying.
Fever in an infant younger than 3 months.
Ear pain or new rash with fever.
Unusual sleepiness or irritability.

Who is at higher risk of flu complications

Some groups face a higher chance of pneumonia, hospital care, or death from flu. They should seek medical advice early if symptoms start:

Adults 65 years and older.
Children under 2 years.
Pregnant and up to 2 weeks postpartum.
People with asthma or chronic lung disease.
Heart disease, diabetes, kidney or liver disease.
Neurologic or neurodevelopmental conditions.
Blood disorders such as sickle cell disease.
People with weakened immune systems.
People with extreme obesity.

If you are in a higher risk group and think you have flu, contact a clinician as soon as symptoms start. Early action helps.

When to test and when to call a clinician

If you feel very unwell, are in a higher risk group, or care for someone at risk, call your clinician. They may order a flu test. A test is most useful within the first 2 to 3 days of symptoms. Testing can guide antiviral treatment and help rule out COVID.

Home COVID tests are widely available. If you have fever and cough, test for COVID too, especially before visiting others.

What to do at home

Most people can manage flu at home. These simple steps help you feel better and protect others.

Rest and fluids. Sleep and hydrate. Aim for pale yellow urine.

Fever and pain relief. Use acetaminophen or ibuprofen as directed. Do not give aspirin to children or teens because of Reye syndrome risk.

Soothe the cough. Warm tea with honey can ease cough for adults and kids over one year. Use lozenges if age appropriate. A humidifier may help.

Nasal care. Saline sprays or rinses relieve stuffiness. Short courses of decongestants can help adults, but avoid if you have heart disease or high blood pressure unless your clinician approves.

Stay home. You are most contagious in the first 3 to 4 days. Stay home until fever free for 24 hours without medicine and symptoms improve.

Watch for changes. If you start to breathe worse, cannot keep fluids down, or feel confused, seek care.

Antiviral medicines

Prescription antivirals, such as oseltamivir and baloxavir, can shorten illness and reduce complications. They work best when started within 48 hours of symptoms. Clinicians may still use them later for people who are hospitalized or at higher risk. Do not use antibiotics for flu. They do not kill viruses.

How flu spreads and when you are contagious

Flu spreads mainly by droplets when a sick person talks, coughs, or sneezes. It can also spread by touching a contaminated surface, then touching your eyes, nose, or mouth. People can spread flu one day before symptoms and up to a week after. Young children and people with weak immune systems can spread it longer.

How long symptoms last

Fever, aches, and chills tend to peak in the first 2 to 3 days. Sore throat and cough can last one to two weeks. Fatigue may outlast other symptoms. If new fever returns after you start to feel better, call your clinician. That can signal a new infection.

Common mistakes to avoid

Waiting too long to seek help when in a higher risk group.
Using antibiotics for a virus.
Giving aspirin to children or teens.
Pushing through work or school while still feverish.
Not checking for dehydration, especially in kids and older adults.

Quick self-care checklist

Use this short list to track your care each day.

Took temperature and noted symptoms.
Drank water or oral rehydration solution.
Took fever or pain medicine as directed.
Did nasal saline or used humidifier if helpful.
Rested and limited activity.
Checked for red flags twice a day.
Stayed home and masked if around others.

Preventing flu

Get vaccinated every year. The flu shot lowers your risk of severe illness. It also helps protect babies, older adults, and people with long term conditions.

Cover coughs and sneezes. Use a tissue or your elbow.

Wash hands often. Use soap and water for 20 seconds. Use sanitizer if needed.

Improve airflow. Open windows or use ventilation when you host others.

Stay home when sick. This protects your family and coworkers.

Example scenarios

You wake with fever, aches, and a dry cough. Start fluids and rest. Take fever medicine. If you are pregnant, over 65, or have asthma, call your clinician that same day to ask about antivirals.

Your 5-year-old has fever and is not drinking. Try small sips every few minutes. If there are no tears when crying or no urination for 8 hours, seek urgent care.

Your cough lingers past 10 days, but fever is gone. This can be normal. If you also feel short of breath or your fever comes back, get checked.

Why it matters

Knowing real flu symptoms helps you act early. Early action lowers the chance of pneumonia and hospital care. It also keeps families safer during peaks. On 2026-01-06, many countries report active flu circulation each winter. A clear plan reduces stress and protects the people you love.