How do I differentiate and manage flu versus cold symptoms?

Differentiating and Managing Cold vs. Flu

Influenza is distinguished from the common cold primarily by the abrupt onset of high fever (>38°C), severe myalgias, and systemic symptoms that confine patients to bed, whereas colds present with gradual onset of predominantly nasal symptoms without significant fever. 1, 2

Clinical Differentiation

Influenza Presentation

• Abrupt onset of fever >38°C, cough, chills or sweats, myalgias, and malaise 3
• Patients typically experience confinement to bed due to severity 2
• Systemic symptoms predominate over localized respiratory symptoms 1
• Almost all patients have cough, sweats, runny nose, and muscle aches, though prominence varies 4

Common Cold Presentation

• Gradual onset with predominantly nasal symptoms 2
• Fever is typically absent or low-grade 2
• Milder systemic symptoms that do not typically confine patients to bed 2
• Perceived as "harmless with individualistic symptoms" 2

Important caveat: Symptom variability makes standard descriptions elusive, and laypersons often misinterpret fever and disease severity 4, 2. Clinical diagnosis alone has poor specificity and sensitivity 4.

Diagnostic Approach

When to Test

• Laboratory confirmation is not necessary for most outpatient cases with typical presentation 3
• Testing is useful for hospitalized patients and when confirmation will change treatment decisions 1, 3
• Rapid molecular assays are preferred—point-of-care, highly accurate, with fast results 3

Severity Assessment

• Immediately assess vital signs, oxygen saturation, and mental status 1, 5
• Use CURB-65 score for pneumonia severity (Confusion, Urea >7 mmol/L, Respiratory rate ≥30/min, Blood pressure <90/60 mmHg, Age ≥65 years) 6, 1, 5
• CRP ≥30 mg/L plus suggestive symptoms increases pneumonia likelihood 1

Management Algorithm

For Suspected Influenza

Step 1: Determine if antiviral therapy is indicated

• Give oseltamivir 75mg twice daily for 5 days if ALL of the following are present: 6, 5
  • Acute influenza-like illness
  • Fever >38°C
  • Symptoms ≤2 days duration
• Reduce dose by 50% if creatinine clearance <30 mL/min 6, 5
• Greatest benefit when started within 24 hours of symptom onset 3
• Reduces illness duration by approximately 24 hours and may reduce hospitalization 5, 3

Step 2: Symptomatic management for ALL patients

• Paracetamol or ibuprofen for fever, myalgias, and headache 6, 1, 7
• Rest and adequate fluid intake 6
• Consider topical decongestants, throat lozenges, saline nose drops 6
• Never aspirin in children <16 years (Reye's syndrome risk) 6, 1

Step 3: Determine if antibiotics are needed

• Do NOT give antibiotics for uncomplicated influenza without pneumonia 6, 1, 5
• Consider antibiotics if: 6, 5
  • Worsening symptoms (recrudescent fever or increasing dyspnea)
  • High-risk patient with lower respiratory features
  • Confirmed or suspected bacterial pneumonia
• Preferred oral choices: co-amoxiclav or tetracycline 6

For Common Cold

• Symptomatic treatment only: paracetamol or ibuprofen for discomfort 7
• Rest and fluids 6
• Topical decongestants if needed 6
• No antibiotics unless bacterial complications develop 6, 1

When to Escalate Care

Red Flags Requiring Re-consultation

• No improvement or worsening 48 hours after starting antivirals 6, 1
• Shortness of breath at rest or with minimal activity 6
• Painful or difficult breathing 6
• Coughing up bloody sputum 6
• Drowsiness, disorientation, or confusion 6
• Fever persisting 4-5 days without improvement 6

Hospital Admission Criteria

Consider admission if ≥2 of the following are present: 6, 5

• Temperature >37.8°C
• Heart rate >100/min
• Respiratory rate >24/min
• Systolic BP <90 mmHg
• Oxygen saturation <90%
• Inability to maintain oral intake
• Abnormal mental status

CURB-65 Score Interpretation

• Score 0-1: Consider home treatment 6, 1, 5
• Score 2: Consider short inpatient stay or hospital-supervised outpatient management 6, 5
• Score ≥3: Manage as severe pneumonia with hospital admission 1, 5

Special Populations

High-Risk Patients (require closer monitoring)

• Chronic respiratory disease (including asthma on inhaled steroids), cardiac disease, renal disease, liver disease 6
• Diabetes requiring medication, immunosuppression, malignancy 6
• Age ≥65 years, pregnancy 6
• Long-stay residential care home residents 6

Children

• Infants <1 year and high-risk children must be assessed by GP or A&E 6
• Children 1-7 years may be seen by nurse or GP 6
• Children ≥7 years may be seen by community health team 6
• Never aspirin in children <16 years 6, 1

Common pitfall: During flu season, increased consultation rates for all respiratory infections can overwhelm services—triage based on severity and risk factors, not all patients need face-to-face consultation 6