Influenza (Flu)

A common viral infection of the nose, throat and lungs that comes on suddenly with fever, aches and tiredness.

InfectionBreathingLast updated: 21 October 2026

Quick Summary

Primary Symptoms

Sudden fever, chills, cough, sore throat, body aches, headache and extreme tiredness.

Common Treatments

Rest, fluids and paracetamol. Antiviral medicine such as oseltamivir for people at high risk or with severe illness.

Risk Factors

Young children, older adults, pregnancy, long-term conditions such as diabetes, asthma and heart disease.

OverviewSymptomsCausesTreatmentFAQ

Overview

Influenza is caused by flu viruses that spread through coughs, sneezes and touching contaminated surfaces. In India, flu peaks during the monsoon and winter.

Most healthy people recover in about a week, but flu can lead to pneumonia and be serious in high-risk groups. A yearly flu vaccine is the best protection.

Symptoms

Sudden fever

Often with chills and sweating.

Body aches

Muscle and joint aches, often severe.

Cough and sore throat

A dry cough that can last for a couple of weeks.

Extreme tiredness

Feeling too unwell to do normal activities.

Causes & Risk Factors

Biological Causes

Infection with influenza A or B viruses. These viruses change over time, which is why the vaccine is updated every year.

Key Risk Factors

  • Age Children under 5 and adults over 65 are at higher risk of complications.
  • Pregnancy Flu can be more severe during pregnancy.
  • Long-term conditions Asthma, COPD, diabetes, heart and kidney disease.

Management & Treatment

01. Rest and fluids

Stay home, rest and drink plenty of fluids.

02. Fever and pain relief

Paracetamol or ibuprofen, if suitable for you.

03. Antivirals

Oseltamivir may be given to people at high risk, ideally within 48 hours of symptoms starting.

Frequently Asked Questions

Is flu the same as a cold?
No. Flu comes on suddenly and makes you feel much more unwell than a cold.
Do antibiotics help?
No. Antibiotics don't work on viruses, unless a bacterial infection develops.
Who should get the flu vaccine?
Especially older adults, pregnant women, young children and people with long-term conditions.

Sources and further reading

Last updated 21 October 2026. For more detail, see these trusted health organisations.