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Pandemic Flu

Pandemic Flu. Clinical Assessment, Triage and Treatment. Dr Graham Douglas Consultant Physician Aberdeen Royal Infirmary. Influenza. Clinical Case Definition.

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Pandemic Flu

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  1. Pandemic Flu Clinical Assessment, Triage and Treatment Dr Graham Douglas Consultant Physician Aberdeen Royal Infirmary

  2. Influenza Clinical Case Definition “The presence of fever and new (or in those with chronic lung disease worsening) cough of acute onset in the context of influenza circulating in the community” NB: This definition may need to be modified once the pandemic appears Clinical diagnosis of ‘typical’ influenza is easy during epidemics/pandemics

  3. Influenza • Incubation period: commonly 2-4 days (range 1-7 days) • Fever is the most important symptom - may reach 41oC - peaks within 24 hrs of onset - typically lasts for 3 days (range 1-5 days)

  4. Influenza RANGE OF SYMPTOMS ASSOCIATED WITH UNCOMPLICATED INFLUENZA INFECTION Cough ~ 85% Anorexia ~ 60% Malaise ~ 80% Coryzal (cold) symptoms ~ 60% Chills ~ 70% Myalgia ~ 53% Headache ~ 65% Sore throat ~ 50% Cough & malaise - persist for 1-2 weeks and up to 6 weeks

  5. Influenza ASSESSMENT IN PRIMARY CARE Majority with uncomplicated influenza will make a full recovery Symptomatic management – Rest Fluids Paracetamol Antibiotics rarely useful

  6. Avian Influenza A/H5N1

  7. Influenza ASSESSMENT IN PRIMARY CARE EXAMPLES OF WHAT SHOULD PROMPT PATIENTS TO RECONSULT • Shortness of breath at rest • Painful or difficult breathing • Coughing up bloody sputum • Fever for 4-5 days and not getting better • Starting to feel better then developing high fever • Drowsiness, disorientation or confusion

  8. Influenza There is no validated severity assessment tool developed specifically for Influenza or Influenza-related Pneumonia

  9. Influenza SEVERITY ASSESSMENT CURB – 65 Score Well known and validated for Community Acquired Pneumonia • Confusion • Urea > 7 mmol/l • Respiratory rate >30/mm • Blood pressure (diastolic < 60mmHg) • >65 years of age Score 1 point for each feature

  10. Pandemic InfluenzaAge and mortality

  11. Influenza SEVERITY ASSESSMENT CRB – 65 Also well validated • 0 Likely to be suitable for home treatment • 1 & 2 Consider hospital referral • 3 & 4 Urgent hospital referral Consider hospital referral if there are bilateral lung crackles

  12. Influenza SEVERITY ASSESSMENT IN HOSPITAL CURB -65 score 3 or more = ‘Severe Pneumonia’ CURB -65 score 4 or more Should be considered for HDU/ITU care Other general indications for HDU/ITU: Hypoxia – pO2<8 despite oxygen Progressive CO2 retention Severe acidosis – pH<7.26 Septic shock Bilateral shadowing on CXR

  13. Influenza COMMON COMPLICATIONS RESPIRATORY • Acute Bronchitis • Secondary Bacterial Pneumonia (~20%) Appears 4-5 days after start of ‘flu Microbiology: • 1918 H.influenza, S.pneumoniae, βhaem.strept • 1957 Staph.aureus (>2/3rds) • 1968 S.pneumoniae, Staph.aureus, H.influenzae (48%) (26%) (11%) • Community MRSA uncommon in Europe/concern in US

  14. Influenza COMMON COMPLICATIONS CVS: • ECG changes 80% (Twave inversion; ‘minor’ rhythm disturbances) CHILDREN: • Otis media EXACERBATION OF PRE-EXISTING DISEASE: • COPD • Bronchiectasis • Heart failure • Diabetes mellitus

  15. Influenza UNCOMMON COMPLICATIONS RESPIRATORY: • Primary viral pneumonia - appears common in human cases of H5N1 - rapid respiratory failure; within 48 hours - mortality >40%; within 7 days CVS: • Myocarditis/pericarditis CNS: • Transverse myelitis/Guillain-Barre • Myositis & Myoglobinuria (Influenza is a multi-system disorder)

  16. Influenza ANTIBIOTICS – WHEN? • Previously well adults - Uncomplicated acute bronchitis – NO - Pneumonia (lung crackles/abnormal CXR) - YES • High risk patients/pre-existing disease - Lower respiratory tract features - YES - Pneumonia - YES

  17. Influenza ANTIBIOTICS – WHICH? • Empirical cover - S.pneumoniae, H.influenzae, S.aureus - YES - Legionella ssp, ‘atypical pathogens’ - NO • Co-amoxiclav or Doxycycline ANTIBIOTICS – HOW? • Oral route for non-severe • IV route for severe infection (CURB 65 > 3)

  18. Antiviral Therapyin ‘Ordinary Flu’ • <30h after onset of symptoms - significant effect on reduction of duration of symptoms esp fever (shorten by 1 day) • >30h after onset of symptoms - no significant effect • No known effect on mortality

  19. Neuraminidase inhibitors • Oseltamivir • Oral • Zanamivir • Dry powder inhaler

  20. Pandemic Influenza EFFICACY OF ANTIVIRALS • Oseltamivir active in vitro and in vivo against previous pandemic strains: H2N2 (1957), H3N2 (1968), N1N1 (1977) etc • But only 1 mutation required for full resistance • Rates of development of resistance to oseltamivir in clinical isolates: - Trials in adults: 0.33% - Trials in children: 4-18% • ? Combining neuraminidase inhibitors with M2 ion channel inhibitors (Amantadine & Rimantadine)

  21. Pandemic Influenza POSSIBLE BENEFITS OF ANTIVIRAL USE IN THE PANDEMIC • Reduction of illness duration by an average of 24hr and therefore more rapid mobilisation of essential workers • Reduction in viral secretion & clinical attack rates • Reduction in hospitalisation • Reduction of complications and therefore need for other drugs especially antibiotics

  22. Pandemic Influenza RECOMMENDATIONS FOR ANTIVIRAL THERAPY • Patients to receive antivirals if they have all of - Acute influenza-like illness - Fever >38oC - Within 30hrs of onset • Oseltamivir (Tamiflu) 75ug bd for 5 days - reduce dose in renal failure - adjust dose by body weight in children (liquid) - avoid in children under 1 year • Currently stockpile for 25% population in Scotland • Logistics!

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