Transcript Avian Flu and the threat of an H5N1 Influenza A pandemic

Hot Topic Meeting by:
Royal College of Physicians of Edinburgh & The
Scottish Executive Health Department
Pandemic Flu
Planning Scotland’s Health Response
5th June 2007
Queen Mother Conference Centre
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
- by risk factors
Uncomplicated:
- by age
- by virus type
THE MENU
Clinical features of:
• Typical influenza A
- milder complications
• Serious complications
- respiratory
- non respiratory
• Variation by pandemic outbreak
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’
)
MILDER COMPLICATIONS OF
INFLUENZA A
- TRACHEOBRONCHITIS
- OTITIS MEDIA
- SINUSITIS
- POST INFLUENZAL ASTHENIA AND
DEPRESSION
Who is at risk of influenza?
‘Typical’ Influenza A:
Pandemic Influenza
• As across
• + young adults
• +pregnant women
Peak mortality 1918
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•
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•
Age <2 >65yrs
Chronic disease : respiratory, cardiac,
renal, diabetes, immunosuppression
‘at risk’ settings
Risk factor influences presentation /
complications
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
Complications of Influenza A
Infection
2y pneumonia due to bacterial suprainfection
The problem :
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
2y bacterial pneumonia
pneumococcus
H.influenza
Staphylococcal pneumonia
complicating Influenza A
A sinister synergy
Complications of Influenza A Virus
Iy Pneumonitis due to virus
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What is role of cytokine storm?
Often fulminant and fatal
Dyspnoea, wheeze, cyanosis,
blood
Diffuse CXR infiltrates (like
ARDS)
Pregnant, cardiac, young
Pandemic Influenza 1918/19
Morbidity
Mortality
• Global mortality 23-50M
• Occurred in 3 waves
• Globally estimated 750m-Ib. ill • UK mortality 240K
• Peak mortality - young adults
1918/19
Spanish ‘flu - Heliotrope cyanosis
“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…”
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
COMPARING PANDEMICS
UK MORTALITY
’18/’19
240k
’57/’58
33k
’68
30k
AGE
Young
Elderly
Elderly
adult
(young)
(young)
S. pyogenes
S. aureus
S. aureus
E+W
‘notable’
BACTERIA
+ others
Hot Topic Meeting by:
Royal College of Physicians of Edinburgh & The
Scottish Executive Health Department
Pandemic Flu
Planning Scotland’s Health Response
5th June 2007
Queen Mother Conference Centre