Influenza (Flu)
Influenza is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. While it can range from mild to severe, it is best prevented through annual vaccination and good hygiene.
Overview
Influenza is a contagious respiratory illness caused by influenza viruses that infect the nose, throat, and lungs. While it can range from mild to severe, it is best prevented through annual vaccination and good hygiene.
Understand this condition
The influenza virus enters the respiratory tract and hijacks cells to replicate itself. This triggers a massive immune response, releasing chemicals that cause inflammation, fever, and muscle aches. The body diverts most of its energy to fighting the virus, leading to extreme fatigue.
Why it happens
The virus spreads through microscopic droplets when an infected person talks, coughs, or sneezes. It targets the lining of the respiratory system, causing cellular damage as it spreads. The illness progresses rapidly as the immune system works to neutralize the invading virus.
Real-world scenarios
- •This often appears as a sudden, high fever with intense shivering.
- •People may notice they are too exhausted to perform basic daily tasks.
- •This often appears as a dry, hacking cough that lingers for weeks.
- •People may notice sudden muscle aches throughout the entire body.
Common vs serious explanations
- •The common cold generally causes milder symptoms and no fever.
- •Allergies involve itchy eyes and sneezing without body aches.
- •Physical exhaustion can cause fatigue but not a high temperature.
- •Mild food poisoning may cause nausea without respiratory distress.
- Pneumonia is a serious lung infection that can follow the flu.
- Myocarditis is an inflammation of the heart muscle caused by viral infection.
- Sepsis is a life-threatening systemic response to the infection.
- Encephalitis is a dangerous inflammation of the brain tissue.
Symptoms
Click any symptom to analyzeNo symptoms mapped yet.
Causes
- •Influenza viruses (Type A and B)
- •Inhalation of infected respiratory droplets
- •Touching contaminated surfaces then touching the face
Risk factors
- •Age (young children and elderly)
- •Pregnancy
- •Weakened immune system
- •Chronic medical conditions (asthma, heart disease)
- •Obesity
How it progresses
3 stages- OnsetSymptoms appear, often triggered by a known cause.Often missed
- Active phaseSymptoms peak; self-care or short treatment usually helps.
- ResolutionSymptoms ease over days to weeks with proper care.
How it's diagnosed
- •Physical examination
- •Rapid influenza diagnostic test (RIDT)
- •Rapid molecular assay (PCR)
- •Clinical symptom assessment
Treatment options
General educational information only — no dosage advice. Always follow guidance from a qualified clinician.
- •Antiviral medications (if started early)
- •Annual flu vaccination for prevention
- •Symptom management (fever reducers)
- •Getting plenty of rest
- •Drinking fluids to stay hydrated
- •Taking over-the-counter pain relievers
- •Staying home to prevent spread
- •Increased fluid intake
Complications
- •Reduced quality of life
- •Worsening symptoms over time
- •Recurrence of influenza (flu)
Prevention
- •Wash hands frequently
- •Avoid close contact with infected people
- •Stay up to date with vaccines
- •Maintain a healthy lifestyle
- •See a clinician for routine check-ups
When to seek help
- •Symptoms persist beyond a few days
- •Symptoms interfere with daily activities
- •New or worsening symptoms appear
- •Concerning changes related to influenza (flu)
- Difficulty breathing or shortness of breath
- Chest pain or pressure
- Sudden confusion or dizziness
- Blue lips or face
- Seizures
In any emergency, call your local emergency number or go to the nearest emergency department.
Real-world questions
- ›Can Influenza (Flu) cause headaches?
- ›Is Influenza (Flu) reversible?
- ›How quickly does Influenza (Flu) progress?
- ›Is Influenza (Flu) hereditary?
- ›Can Influenza (Flu) be prevented?
Compare conditions
Explore related symptoms
Frequently asked questions
Possible causes of Influenza (Flu) include Influenza viruses (Type A and B), Inhalation of infected respiratory droplets, Touching contaminated surfaces then touching the face.
Influenza (Flu) is generally moderate, but severity can vary. Seek care if symptoms are severe or persistent.
Duration varies between individuals. Many cases improve with appropriate care, while others may persist longer and require ongoing management.
Some milder cases may improve with rest and self-care. If symptoms persist or worsen, consult a healthcare professional.
Consider seeing a clinician if symptoms are severe, persistent, worsening, or if you have any concerns related to general.
Sources
Information based on general medical references such as:
Last reviewed: May 2026