Influenza.

Overview

Influenza is a viral respiratory illness that may cause fever, cough, body aches and fatigue. It can be serious for some people.

A condition may appear differently between people, so a symptom list alone cannot establish a diagnosis. Age, medical history and other circumstances affect assessment.

Signs and symptoms

Influenza often begins with fever or chills, cough, muscle aches, headache, sore throat and marked fatigue. Not everyone has a fever. Some people—especially young children, older adults and those with chronic conditions—can develop complications. Trouble breathing or dehydration calls for prompt medical care.

Causes and risk factors

Flu viruses spread through respiratory particles and contact; seasonal patterns vary.

Risk factors do not guarantee that a person will develop this condition, and a diagnosis can occur even without obvious risk factors.

Diagnosis and tests

Clinical assessment and testing may be used when results would change care.

Tests are chosen for the individual situation. No picture or AI-generated response can confirm this condition.

Care and treatment

Vaccination, preventive measures and, for selected people, timely antiviral treatment can reduce risk.

Treatment plans must consider severity, other illnesses, medication safety and personal preferences. Do not start or change prescribed treatment using this article alone.

Prevention and daily living

Seasonal vaccination and infection-control practices can reduce risk. Some people benefit from early antiviral treatment, particularly when at high risk; discuss rapidly with a clinician when indicated.

Individual care plans may differ, particularly in pregnancy, childhood, older age or when other illnesses are present. The linked clinical source provides more context.

When to seek help

Difficulty breathing, chest pain, dehydration or confusion requires prompt medical attention.

If symptoms are severe, rapidly worsening or you feel unsafe, seek local emergency services. Do not wait for an online reply.

Questions for a clinician

What evidence supports this diagnosis? What tests are necessary? Which treatment options fit my situation? What should I monitor? When should I return or seek urgent help?