The flu, short for influenza, is a respiratory illness caused by influenza viruses that circulate globally each year. Symptoms of the flu 2018 remain consistent with typical flu patterns in other years and include sudden fever, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, and fatigue. Some people also experience vomiting and diarrhea, though this is more common in children. Symptoms often come on suddenly and can last about one week, though fatigue and cough may persist longer. Recognizing these signs early helps you seek timely care and reduce spread to others.
How the Flu Spreads
Influenza viruses spread mainly when people with the flu cough, sneeze, or talk and release droplets into the air that can land in the mouths or noses of people nearby. You can also become infected by touching a surface or object that has virus on it and then touching your own mouth, nose, or eyes. People may be contagious beginning about 1 day before symptoms develop and up to 5–7 days after becoming sick, with children and people with weakened immune systems potentially contagious for longer.
Seasonal patterns
Flu activity often rises in the fall and peaks during winter, though circulation can vary by region and from year to year. Annual vaccination ahead of each season is the best way to reduce the risk of illness, hospitalization, and complications.
Common Flu Symptoms
Flu symptoms can vary in intensity but often include a combination of the following. Not everyone will experience all symptoms, and other illnesses can cause similar signs.
- Fever or feeling feverish (not everyone with the flu will have a fever)
- Cough, often dry
- Sore throat
- Runny or stuffy nose
- Muscle or body aches
- Headaches
- Fatigue (tiredness) that can be severe
- Some people may have vomiting and diarrhea, more common in children
Sudden Onset and Duration
Flu symptoms usually come on suddenly and can make you feel quite ill. While many people recover within a week, some symptoms such as cough and fatigue may linger for days or weeks after the acute illness. Complications can include pneumonia, worsening of chronic medical conditions, and in severe cases, hospitalization or death, particularly in older adults, young children, pregnant people, and those with certain underlying health conditions.
Flu vs cold: quick comparison
| Feature | Flu | Common Cold |
|---|---|---|
| Onset | Sudden | Gradual |
| Fever | Common; often high | Rare |
| Body aches | Often moderate to severe | Uncommon or mild |
| Fatigue | Can be severe | Mild to moderate |
| Sneezing, runny nose | Sometimes | Common |
When to Seek Medical Care
Contact a healthcare professional if you or your child experience any of the following: difficulty breathing or shortness of breath, persistent chest pain or pressure, sudden dizziness, confusion, severe or persistent vomiting, fever with a rash, or if flu-like symptoms improve but then return with fever and worsened cough. These can be signs of serious complications that need prompt evaluation. People at higher risk for flu complications should consult a clinician early when they have flu symptoms, as antiviral medications may be recommended within the first 48 hours of illness.
Emergency warning signs
Seek emergency medical care right away for:
- Fast breathing or trouble breathing
- Bluish lips or face
- Chest pain or pressure
- New confusion
- Severe muscle pain or weakness
- Not waking up or not interacting when awake
Prevention and When You Might Still Be Contagious
Annual influenza vaccination is the most effective way to reduce the risk of flu illness and its complications. Other everyday preventive actions include staying home when sick, covering coughs and sneezes, frequent handwashing, and avoiding close contact with others when you are ill. You should stay home for at least 24 hours after your fever is gone without the use of fever-reducing medicines and follow workplace or school guidance about when it is safe to return.
Recovery and Self-Care
Most people with the flu recover at home by resting, drinking plenty of fluids, and managing symptoms with over-the-counter medicines as needed. Antiviral drugs may shorten illness duration and lower risk of complications when started early, especially for people at higher risk. If symptoms are severe or not improving as expected, contact your clinician for guidance and to discuss whether testing or treatment is appropriate.
Common Questions
- Can I have the flu without a fever? Yes. Some people, particularly older adults and those with weakened immune systems, may have flu symptoms without a fever.
- How long are flu symptoms contagious? Many people can spread the virus from about 1 day before symptoms appear and up to 5–7 days after becoming sick, though this varies by age and immune status.
- Is the flu the same as COVID-19? No. They are caused by different viruses and can have overlapping symptoms. Testing can help determine the cause and guide care.
Bottom line
Symptoms of the flu typically include fever, cough, sore throat, runny nose, muscle aches, headaches, and fatigue, with sudden onset that can make you feel quite ill for a few days. Recovery often takes about a week, though cough and tiredness may last longer. Annual vaccination, early antiviral treatment when appropriate, and knowing when to seek medical care are key steps to reduce complications and protect others.