Educational information, not medical advice. See our Medical Disclaimer. Last updated: October 11, 2026.
Seasonal influenza (“the flu”) returns every year in temperate regions, typically in autumn and winter in the Northern Hemisphere. For most healthy people it is a miserable week and then over. For others, including older adults, young children, pregnant women and people with chronic conditions, it can lead to serious complications. This guide covers how to recognize flu, how to lower your chances of catching or spreading it, and what to do if you get it.
Flu symptoms
Flu symptoms typically come on suddenly and can include:
- Fever or chills (not everyone with flu has a fever)
- Cough and sore throat
- Runny or stuffy nose
- Muscle and body aches
- Headache
- Marked tiredness
- Vomiting and diarrhea, which are more common in children
Flu or cold?
Both are respiratory infections, but the NHS notes some typical differences. Flu appears within hours, a cold builds over a day or two. Flu affects the whole body and often leaves you exhausted and too unwell for normal activities, while a cold mainly affects the nose and throat and you can usually keep going. The only way to be certain is a test, which is not usually needed for healthy people with mild illness.
Who is at higher risk of complications
The CDC and the World Health Organization (WHO) identify these groups as higher risk of severe illness:
- Adults aged 65 and older
- Children under 5, especially under 2
- Pregnant women
- People with chronic conditions such as asthma, diabetes or heart disease
- People with weakened immune systems
- People with a body mass index of 40 or higher
- Health and care workers, who face higher exposure
Prevention: vaccination and hygiene
Vaccination. WHO calls vaccination the best way to prevent influenza and recommends it annually, because immunity wanes and circulating strains change, so vaccines are updated each year. Effectiveness varies from season to season, often cited in the range of about 40 to 60% in well-matched years, and the vaccine may work less well in older adults. Even when it does not prevent infection, it reduces the severity of illness and the risk of complications and death. In the Northern Hemisphere, vaccination is usually offered from early autumn, so now is a good time to ask your doctor or pharmacist what is available and who is eligible in your country.
Everyday hygiene. WHO advises:
- Wash and dry your hands regularly.
- Cover your mouth and nose when you cough or sneeze, and dispose of tissues properly.
- Stay home when you are unwell.
- Avoid close contact with sick people.
- Avoid touching your eyes, nose and mouth.
Treatment and self-care
Most people recover without specific treatment, usually in about a week. Self-care includes:
- Rest and sleep.
- Fluids. Drink enough to keep urine pale; fever and sweating increase fluid loss.
- Medicines for fever and aches. Paracetamol or ibuprofen can help, following the label. Do not take paracetamol on top of a “cold and flu” remedy that already contains it. See our guide to paracetamol dosage and safety.
- Avoid aspirin in children under 16.
- Antibiotics do not work on flu because it is caused by a virus. They are only used if a bacterial complication develops, as decided by a doctor.
Antiviral medicines such as oseltamivir are available on prescription. They work best when started early, ideally within about two days of symptoms starting. WHO recommends that people with severe illness, and those at high risk, receive antivirals as soon as possible. If you are in a higher-risk group and think you have flu, contact a doctor early rather than waiting.
When to get medical help
Contact a doctor or your local urgent advice service if:
- You are worried about a baby’s or child’s symptoms.
- You are 65 or older, pregnant, or have a long-term condition or weakened immune system.
- You feel very unwell or short of breath.
- Symptoms have not improved after about 7 days.
Call emergency services or go to the emergency department for sudden chest pain, severe difficulty breathing, coughing up blood, confusion, bluish lips, or signs of severe dehydration. Do not drive yourself.
How long are you contagious?
According to the CDC, people are most contagious in the first three days of illness. Some healthy adults can spread flu from one day before symptoms start to five to seven days after becoming sick. Young children and people with weakened immune systems may be contagious for longer. Stay home until you feel better and your fever has gone, and keep away from vulnerable people.
- Flu comes on suddenly and affects the whole body; colds build slowly and are milder.
- Annual vaccination is the best prevention; hand hygiene and staying home when sick also help.
- Antibiotics do not treat flu. Rest, fluids and fever medicines are the mainstay.
- Antivirals work best when started early and are especially important for higher-risk people.
- Seek urgent care for breathing difficulty, chest pain, confusion or symptoms in vulnerable groups.
Frequently asked questions
Can the flu vaccine give me the flu?
No. Injected flu vaccines do not contain live virus that can cause flu. Mild, short-lived side effects such as a sore arm or low fever can occur.
Is “stomach flu” the same as influenza?
No. “Stomach flu” usually refers to gastroenteritis caused by other viruses or bacteria. Influenza is a respiratory illness, although vomiting and diarrhea can occur, mostly in children.
Do vitamin C or other supplements prevent flu?
There is no good evidence that supplements reliably prevent influenza. Vaccination, hygiene and a healthy lifestyle matter more, including good sleep and a balanced diet.
Can I go to work with the flu?
You are most contagious in the first days of illness, and flu usually leaves people too unwell to work effectively. Staying home protects colleagues, especially vulnerable ones.
Sources
Written by the nohas.es Editorial Team from the official sources listed above. Read our Editorial Policy and Fact Checking Policy. Found an error? Tell us.
