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Clinical characteristics of ‘Flu’

Clinical characteristics of ‘Flu’. Dr Dermot H Kennedy Consultant Physician in Infectious Diseases (Retd.) Glasgow. “Influenza A is an unvarying disease due to a varying virus” E. Kilbourne New York 1975. Variation Complicated: - by pandemic virus - by co-infecting bacteria

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Clinical characteristics of ‘Flu’

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  1. Clinical characteristics of ‘Flu’ Dr Dermot H Kennedy Consultant Physician in Infectious Diseases (Retd.) Glasgow

  2. “Influenza A is an unvarying disease due to a varying virus”E. Kilbourne New York 1975 Variation Complicated: - by pandemic virus - by co-infecting bacteria - by risk factors Uncomplicated: - by age - by virus type

  3. THE MENU Clinical features of: • Typical influenza A - milder complications • Serious complications - respiratory - non respiratory • Variation by pandemic outbreak

  4. Clinical Spectrum of Influenza A Incidence / range of systemic features Collated from 10 studies of 520 virologically confirmed adult cases 1937-1992 ( after Nicholson Ch. 19 in ‘Human Influenza’ )

  5. MILDER COMPLICATIONS OF INFLUENZA A - TRACHEOBRONCHITIS - OTITIS MEDIA - SINUSITIS - POST INFLUENZAL ASTHENIA AND DEPRESSION

  6. ‘Typical’ Influenza A: Pandemic Influenza • As across • + young adults • +pregnant women • Age <2 >65yrs • Chronic disease : respiratory, cardiac, renal, diabetes, immunosuppression • ‘at risk’ settings • Risk factor influences presentation / complications Who is at risk of influenza? Peak mortality 1918

  7. SERIOUS COMPLICATIONS OF INFLUENZA A RESPIRATORY: . 2y bacterial pneumonia . 1y viral pneumonitis . Mixed viral and bacterial pneumonia . Exacerbation of COAD, asthma NON RESPIRATORY: . CNS eg encephalopathy, myositis . CARDIAC eg decompensated CCF

  8. The problem : Complications of Influenza A Infection 2y pneumonia due to bacterial suprainfection

  9. 2y BACTERIAL PNEUMONIA • Influenza A accounts for 5→10% of all C.A.P. • Biphasic disease – usually • Pattern different from “CAP norm”, and between pandemics • Pneumococcal pneumonia commonest

  10. pneumococcus H.influenza 2y bacterial pneumonia

  11. A sinister synergy Staphylococcal pneumonia complicating Influenza A

  12. Complications of Influenza A Virus • Often fulminant and fatal • Dyspnoea, wheeze, cyanosis, blood • Diffuse CXR infiltrates (like ARDS) • Pregnant, cardiac, young Iy Pneumonitis due to virus What is role of cytokine storm?

  13. Morbidity Mortality • Global mortality 23-50M • UK mortality 240K • Peak mortality - young adults • Occurred in 3 waves • Globally estimated 750m-Ib. ill Pandemic Influenza 1918/19

  14. “We have always been thankful when (facial) colour remains red …there is ample room for hope of recovery When the colour of the patient’s face is heloitrope or mauvy-blue the prospect is grave indeed…” 1918/19 Spanish ‘flu - Heliotrope cyanosis

  15. Features Avian Influenza H5/N1 - Z genotype traced to geese in Guangdong, China 1996 1997: Hong Kong - 6/18 fatal (33%) 2003/7: Asia - 175/290 fatal (60%) Majority < 25yr old Severe disease in: older, late presentation + pneumonia, leuko/lymphopenia (16%) • Vietnamese cases – encephalopathy + diarrhoea • Multi system involvement and Multi organ damage at Post Mortem

  16. COMPARING PANDEMICS ’18/’19 ’57/’58 ’68 UK MORTALITY 240k 33k 30k E+W AGE YoungElderly Elderly adult (young) (young) ‘notable’ S. pyogenes S. aureus S. aureus BACTERIA + others

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