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Fever and Flu-Like Illness

Fever and flu-like symptoms are very common and can be caused by a wide range of viral respiratory infections. Symptoms may include raised temperature, aches, cough, fatigue, sore throat and generalised discomfort. Most cases improve within a few days, although some people may feel tired for longer.

These articles are intended as educational sources, not diagnostic nor taking place of a proper medical assessment. If you need help, please book an appointment with one of our GP’s.

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What a What Fever and Flu-Like Illness Means

Fever is the body’s natural response to inflammation or infection. Flu-like illness refers to a group of symptoms that often occur together, such as:

  • raised temperature
  • muscle aches
  • headache
  • cough or sore throat
  • blocked or runny nose
  • tiredness

These symptoms are usually caused by viral infections, especially during winter months. They often settle without treatment and most cases improve without treatment.

What is the difference between a cold and flu?

Colds and flu share many symptoms, but there are some general patterns that people may notice. These features are not diagnostic and can overlap, but may help you understand typical differences seen in viral illnesses.

Feature Cold Flu (Influenza)
Onset Gradual Sudden, symptoms may appear within hours
Temperature Normal or mild fever Higher fever more common
Aches Mild aches or discomfort More pronounced body aches
Fatigue Mild tiredness Moderate to severe fatigue, may last longer
Respiratory symptoms Runny nose, sneezing, sore throat Cough, chest discomfort, sore throat
Speed of recovery Usually improves within a few days Symptoms may last longer and be more intense

Common Symptoms of Flu-Like Illness

You may experience:

  • Fever
  • Body aches and muscle soreness
  • Fatigue or exhaustion
  • Headache or eye pressure
  • Runny or blocked nose
  • Cough, dry or productive
  • Sore throat or hoarse voice
  • Feeling cold or shivery
  • Loss of appetite
  • Mild stomach upset or nausea

Tiredness can last longer than other symptoms, even once the fever improves.

Common Reasons to Have Fever or Flu-Like Symptoms Reviewed by a GP

Speak to a GP if you have:

  • Symptoms are not improving after 3 to 5 days
  • Fever is lasting longer than 72 hours
  • Cough persists for more than 3 weeks
  • You have existing medical conditions such as asthma, COPD, diabetes or heart disease
  • Symptoms seem out of proportion to a usual cold
  • Symptoms improve but then worsen again
  • You are unsure whether further tests are needed

A GP can assess your symptoms, review your health history and advise on next steps.

Common Viruses and Secondary Bacterial Causes

Type Organism Notes
Viral Influenza A & B Common cause of sudden flu-like illness with fever and aches.
Viral RSV Can cause cough, fever and breathing symptoms.
Viral Rhinoviruses Common cause of colds that may include mild fever.
Viral Seasonal coronaviruses Often produce mild to moderate flu-like symptoms.
Bacterial Streptococcus pneumoniae Sometimes associated with persistent fever and respiratory symptoms.
Bacterial Haemophilus influenzae Occasionally linked to extended respiratory symptoms.

Severe Symptoms – Seek Urgent Help

Seek urgent medical care if you develop:

  • Difficulty breathing or breathlessness
  • Chest pain, especially if central or heavy
  • Confusion, reduced alertness or drowsiness
  • Severe dehydration or inability to hold down fluids
  • A rash that does not fade when pressed
  • Very high fever with shaking chills
  • Symptoms that rapidly worsen

These may indicate a more serious condition requiring immediate assessment.

Understanding Typical Symptom Patterns

Patterns that often suggest a simple viral illness

  • Fever that settles within 1–3 days
  • Runny nose or sore throat followed by cough
  • Mild to moderate body aches
  • Fatigue improving gradually
  • Normal breathing at rest

These are typical of seasonal viral infections.

Symptoms that need a GP review

  • Fever lasting longer than 3 days
  • New breathlessness or chest tightness
  • Cough persisting beyond 3 weeks
  • Symptoms worsening instead of improving
  • Difficulty sleeping or eating due to symptoms
  • Recurrent episodes within a short timeframe

A GP can guide you on treatment or further assessment if needed.

When Prescribed Medication May Be Considered

Most fever and flu-like illnesses are viral, and antibiotics are not required. A GP may consider antibiotics only when:

  • symptoms suggest possible bacterial chest involvement
  • fever is not settling after several days
  • assessment findings that raise concern
  • you have conditions that increase risk

How GPs Assess Flu-Like Symptoms

GPs consider:

  • temperature pattern
  • duration of illness
  • breathing and oxygen levels
  • chest examination
  • history of asthma, COPD or other long-term conditions
  • hydration status
  • response to simple measures

Further tests are only arranged when clinically indicated.

How Viral Illness is Managed

Management may include:

  • rest and adequate fluids
  • simple pain or fever relief if appropriate
  • staying warm and hydrated
  • reducing exposure to smoke or irritants
  • monitoring breathing, hydration and temperature
  • returning for review if symptoms do not improve

A secondary bacterial infection can develop from viral illnesses. If simple measures aren’t helping, speak to a GP.

Related articles

Further Reading and Hub Links

Visit our Common Infections hub or browse more health topics in the AccessGP Knowledge Base.

If you would like to discuss fever, flu-like symptoms or ongoing illness, you can book an online GP appointment with AccessGP.

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Last reviewed by Dr Zamiel Hussain, GMC registered GP
Updated: 9 December 2025