Doctors Revision

Respiratory System

Influenza

An acute viral respiratory illness caused by influenza viruses (Types A, B, C). Typically occurs in seasonal epidemics. Characterized by abrupt onset of systemic symptoms (fever, myalgia, headache) and respiratory symptoms.

Also known as: Flu

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Referral and warning signs

When to refer

Referral to hospital (H/RR) for: Severe symptoms (dyspnoea, hypoxia, altered mental status, dehydration). Signs of complications (pneumonia). High-risk patients with significant symptoms. Worsening illness despite supportive care.

Red flags

  • Difficulty breathing or shortness of breath
  • Chest pain or pressure
  • Sudden dizziness or confusion
  • Severe or persistent vomiting
  • High fever unresponsive to antipyretics
  • Worsening of chronic medical conditions
  • Cyanosis

Signs and symptoms

  • Sudden onset.
  • Fever (often high, 38-40°C) and chills/shivering.
  • Myalgia (muscle aches) and arthralgia (joint aches) - often prominent.
  • Headache.
  • Malaise, fatigue, weakness (can be significant).
  • Non-productive, harsh cough.
  • Sore throat.
  • Rhinitis (runny/stuffy nose).
  • Anorexia, sometimes nausea/vomiting.

Risk factors

  • Exposure to infected individuals (droplet transmission).
  • Seasonal epidemics (typically during cooler/rainy seasons).
  • Crowded settings.
  • Age extremes (young children, elderly >65).
  • Chronic medical conditions (lung disease, heart disease, kidney disease, liver disease, diabetes, immunosuppression, neurological disorders).
  • Pregnancy (especially 2nd/3rd trimester) and postpartum.
  • Obesity.
  • Residents of nursing homes/long-term care facilities.

Diagnosis

Clinical assessment

Diagnosis usually clinical during influenza season/epidemics based on characteristic abrupt onset of fever plus systemic symptoms (myalgia, headache, malaise) and respiratory symptoms (cough, sore throat, rhinitis). Differentiate from common cold (coryza - less abrupt, lower fever, less myalgia), bacterial pneumonia (productive cough, focal chest signs), Strep throat, COVID-19.

Investigations

  • Usually not required for typical uncomplicated cases.
  • Rapid influenza diagnostic tests (RIDTs) or Rapid molecular assays on nasopharyngeal swab: Can confirm diagnosis quickly but sensitivity varies. Useful for public health surveillance or guiding antiviral use in high-risk patients/hospital settings.
  • RT-PCR for influenza virus: More sensitive and specific, reference standard (usually specialized labs).
  • Chest X-ray: If pneumonia suspected.

Diagnostic criteria

Clinical diagnosis based on typical symptoms during periods of known influenza activity. Laboratory confirmation possible but often not necessary for outpatient management.

Management

Non-pharmacological management

  • Symptomatic Relief:
  • - Rest.
  • - Adequate fluid intake.
  • - Humidified air/steam inhalation.
  • - Throat lozenges/salt water gargles.
  • Infection Control:
  • - Stay home from work/school until fever-free for 24h without antipyretics.
  • - Cover coughs/sneezes.
  • - Frequent handwashing.

Pharmacological treatment

  • Analgesia/Antipyretics: Paracetamol or NSAIDs for fever, headache, myalgia.
  • Antiviral Medications (Neuraminidase inhibitors - Oseltamivir, Zanamivir; Baloxavir):
  • - Recommended for patients with severe, complicated, or progressive illness, or those hospitalized.
  • - Consider for outpatients at high risk for complications (see risk factors) if treatment can be started within 48 hours of symptom onset.
  • - Oseltamivir (Tamiflu): Standard adult dose 75mg PO BID for 5 days (adjust for renal impairment/children).
  • - Routine antiviral treatment NOT recommended for healthy individuals with uncomplicated influenza.
  • Antibiotics: NOT indicated for uncomplicated influenza (viral illness). Only use if secondary bacterial complication (e.g., pneumonia, otitis media) is suspected/confirmed.

Monitoring

  • Monitor for symptom improvement (fever usually lasts 2-5 days, cough/fatigue may persist longer).
  • Monitor for signs of complications (worsening dyspnoea, productive cough, persistent fever).

Complications

  • Secondary bacterial pneumonia (Streptococcus pneumoniae, Staphylococcus aureus, Haemophilus influenzae)
  • Viral pneumonia
  • Exacerbation of underlying chronic conditions (asthma, COPD, HF)
  • Sinusitis
  • Otitis media
  • Myositis, Rhabdomyolysis (rare)
  • Encephalitis, Myocarditis, Pericarditis (rare)
  • Sepsis

Prevention

  • Annual Influenza Vaccination: Most effective prevention method. Recommended especially for high-risk groups and healthcare workers.
  • Hand hygiene.
  • Respiratory etiquette (cover coughs/sneezes).
  • Avoid close contact with sick individuals.
  • Antiviral chemoprophylaxis (Oseltamivir): May be considered for high-risk individuals after close exposure, or for controlling institutional outbreaks (specialist guidance).

Patient education

  • Explain influenza vs common cold.
  • Viral nature - antibiotics not effective.
  • Focus on rest, fluids, symptom relief.
  • How to prevent spread (handwashing, cover cough).
  • When to seek medical attention (red flags, complications).
  • Importance of annual flu vaccination for prevention.
  • Proper use of antivirals if prescribed.

Uganda-specific notes

Influenza surveillance exists but diagnostic testing capacity is limited. Clinical diagnosis based on epidemic patterns is common. Secondary bacterial pneumonia is a significant complication. Vaccination uptake may be low.

References

  • Uganda Clinical Guidelines (UCG) 2023

    Chapter 5, Section 5.2.5

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