The 2009-2010 A(H1N1v) pandemic Situation report Europe and forward look to the autumn Zsuzsanna...
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Transcript of The 2009-2010 A(H1N1v) pandemic Situation report Europe and forward look to the autumn Zsuzsanna...
The 2009-2010 A(H1N1v) pandemic
Situation report Europe and forward look to the autumnZsuzsanna Jakab, DirectorEuropean Centre for Disease Prevention and Control
Swedish Presidency Workshop, Jönköping, 2-3 July 2009
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Pandemics of influenza
H7
H5
H9*
1980
1997
Recorded new avian influenzas
1996 2002
1999
2003
1955 1965 1975 1985 1995 2005
H1N1
H2N2
1889Russianinfluenz
aH2N2
H2N2
1957Asian
influenzaH2N2
H3N2
1968Hong Konginfluenza
H3N2
H3N8
1900Old Hong
Kong influenza
H3N8
1918Spanishinfluenza
H1N1
1915 1925 1955 1965 1975 1985 1995 20051895 1905 2010 2015
2009Novel
influenzaH1N1v
Recorded human pandemic influenza(early sub-types inferred)
Reproduced and adapted (2009) with permission of Dr Masato Tashiro, Director, Center for Influenza Virus Research, National Institute of Infectious Diseases (NIID), Japan.
Animated slide: Press space bar
H1N1
H1N1v
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Situation report Europe,as of 1 July 2009
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Cumulative distribution of confirmed cases of A(H1N1)v by day of reporting, as of 29 June 2009, log scale
1
10
100
1 000
10 000
100 000
26/04/09 03/05/09 10/05/09 17/05/09 24/05/09 31/05/09 07/06/09 14/06/09 21/06/09 28/06/09
France
Germany
Spain
UK
Num
ber
of
case
s, logari
thm
ic
scale
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Selected European countries
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The situation could be a lot worse for Europe! (Situation circa summer 2009) A pandemic strain emerging in the
Americas Immediate virus sharing so rapid
diagnostic and vaccines Based on A(H1N1)v currently not that
pathogenic Some seeming residual immunity in a
major large risk group No known pathogenicity markers Initially susceptible to oseltamivir Good data and information coming out of
North America Arriving in Europe in the summer Milder presentation initially
A pandemic emerging in SE Asia
Delayed virus sharing
Based on a more pathogenic strain, e.g. A(H5N1)
No residual immunity
Heightened pathogenicity
Inbuilt antiviral resistance
Minimal data until transmission reached Europe
Arriving in the late autumn or winter
Severe presentation immediately
Contrast with what might have happened — and might still happen!
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But no room for complacency (Situation and information: late May 2009) Pandemics take some time to get going (1918 and
1968). Some pandemic viruses have ‘turned nasty’ (1918
and 1968). Is the ‘mildness’ and the lack of older patients
because older people are resistant or because the virus is not transmitting much among them?
There will be victims and deaths — as in the US — in risk groups (young children, pregnant women and especially people with other underlying illnesses).
As the virus spreads south, will it exchange genes with seasonal viruses that are resistant: A(H1N1)-H247Y, more pathogenic A(H3N2), or even highly pathogenic A(H5N1)?
An inappropriate and excessive response to the pandemic could be worse than the pandemic itself.
7
So far in Europe
A mild disease in most people Easy to miss in surveillance Some severely ill and starting to see deaths – mostly
in people with other underlying conditions Few cases in people over 60 years Spreading efficiently Out-breaks in schools (or easier to see in schools?)
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Initial experience in North America 2009 – the default position
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Emerging themes in North America, early June 2009 (1) Early epidemic about 1 million infected ( = 0.3% of
population) – compared to minimum 25% expected attack rate Infection rate for probable and confirmed cases highest in
5−24 year age group. Hospitalisation rate highest in 0−4 year age group, followed
by 5−24 year age group. – Pregnant women, some of whom have delivered prematurely,
have received particular attention but data inadequate to determine if they are at greater risk from H1N1v than from seasonal influenza as already established.
Most deaths in 25−64 year age group; most with known risks for severe disease.
– Morbid obesity a risk but may be indicator for pulmonary risk. Adults, especially 60 years and old, may have some degree of
preexisting cross-reactive antibody to the novel H1N1 flu virus.
Transmission persisting in several regions of the U.S. Expected to run on throughout the summer and then
accelerate.
10
Emerging themes in North America, end June 2009 (2) Containment impossible with multiple introductions and R0
1.4 to 1.6. Focus on counting laboratory-confirmed cases changing to
seasonal surveillance methods.– Outpatient influenza-like illness, virological surveillance
(including susceptibility), pneumonia and influenza mortality, pediatric mortality and geographic spread.
Serological experiments and epidemiology suggest 2008–2009 seasonal A(H1N1) vaccine does not provide protection.
Preparing for the autumn and winter when virus is expected to return.
Communication difficulty — a pandemic may be 'mild' yet cause deaths
– 25% of U.S. stockpile deployed to states (includes medication and equipment)
– determining who to give vaccine, if and when to begin using vaccine
– school closures being analysed to determine effectiveness
11
Forward look for Europe
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Idealised curve for planningReality is never so smooth and simple
Single wave profile showing proportion of new clinical cases, consultations, hospitalisations or deaths by week. Based on London, 2nd wave 1918.
0%
5%
10%
15%
20%
25%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Week
Pro
port
ion
of
tota
l ca
ses,
con
sult
ati
on
s, h
osp
italis
ati
on
s or
de
ath
s
Source: Department of Health, UK
Initiation Acceleration Peak Declining
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One possible European scenario — summer and autumn 2009
In reality, the initiation phase can be prolonged, especially in the summer months. What cannot be determined is when acceleration takes place.
0%
5%
10%
15%
20%
25%
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar
Month
Pro
port
ion
of
tota
l ca
ses,
con
sult
ati
on
s, h
osp
italis
ati
on
s or
death
s
Initiation Acceleration Peak Declining
Apr
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One possible European scenario — summer 2009
July
August
October
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August
September
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Some of the 'known unknowns' inthe 20th century pandemics Three pandemics (1918, 1957, 1968) Each quite different in shape and
waves Some differences in effective
reproductive number Different groups affected Different levels of severity including
case fatality ratio Imply different approaches to
mitigation
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1918/1919 pandemic: A(H1N1) influenza deaths, England and Wales
1918/19: ‘Influenza deaths’, England and Wales. The pandemic affected young adults, the very young and older age groups.
0
2,000
4,000
6,000
8,000
10,000
12,000
14,000
16,000
18,000
27
29
31
33
35
37 39
41
43
45
47
49
51 2 4 6 8 10
12
14
16
18
1918 1919Week no. and year
Death
s in
Engla
nd a
nd W
ale
s
Ro = 2-3 (US) Mills, Robins, Lipsitch (Nature 2004)Ro = 1.5-2 (UK) Gani et al (EID 2005)Ro = 1.5-1.8 (UK) Hall et al (Epidemiol. Infect. 2006)Ro = 1.5-3.7 (Geneva) Chowell et al (Vaccine 2006)
Courtesy of the Health Protection Agency, UK
Transmissibility: estimated Basic Reproductive Number (Ro)
17
1957/1958 pandemic: A(H2N2) — especially transmitted among children
Ro = 1.8 (UK) Vynnycky, Edmunds (Epidemiol. Infect.2007)Ro = 1.65 (UK) Gani et al (EID 2005)Ro = 1.5 (UK) Hall et al (Epidemiol. Infect. 2006)Ro = 1.68 Longini et al (Am J Epidem 2004)
0
200
400
600
800
1,0006 13
20
27 3 10
17
24
31 7 14
21
28 5 12
19
26 2 9 16
23
30 7 14
21
28 4 11
18
25 1 8 15
22
July August September October November December January February
Week number and month during the winter of 1957/58
Reco
rded d
eath
s in
Engla
nd a
nd W
ale
s fr
om
influenza
1957/58: ‘Influenza deaths’, England and Wales
Courtesy of the Health Protection Agency, UK
Transmissibility: estimated Basic Reproductive Number (Ro)
18
So what can we expect in our countries?
Some features from the ECDC risk assessment
19
It will vary from place to place – and local can be more intense than national
In reality, larger countries can experience a series of shorter but steeper local epidemics.
0%
5%
10%
15%
20%
25%
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Week
Pro
port
ion
of
tota
l ca
ses,
con
sult
ati
on
s, h
osp
italis
ati
on
s or
de
ath
s
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0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
1918 NewYork State
1918Leicester
1918Warringtonand Wigan
1957 SELondon
1968Kansas City
clin
ical
atta
ck r
ate
(%)
Numbers affected in seasonal influenza epidemics and pandemics (overall clinical attack rate in previous pandemics)
Seasonalinfluenza
21
Seasonal influenza compared to pandemic — proportions of types of cases
Asymptomatic
Clinicalsymptoms
Deaths
Requiring hospitalisation
Seasonal influenza Pandemic
Asymptomatic
ClinicalsymptomsDeaths
Requiring hospitalisation
There will be pressure on the primary and secondary health services – especially paediatric and intensive care.
22
Good news
Older people spared Sensitive to antivirals No pathogenicity markers
But influenza is promiscuous – will it pick up any ‘bad’ genes on its winter holiday in the south – primary oseltamivir resistance from seasonal flu or even pathogenicity genes from ‘bird flu’ A(H5N1).
23
Measuring the severity of a pandemic
24
There is an expectation that pandemics should be graded by severity But there are difficulties: Severity varies from country to country. It can change over time. Some relevant information is not available initially. Key health information includes medical and
scientific information:– epidemiological, clinical and virological
characteristics There are also social and societal aspects:
– vulnerability of populations;– capacity for response;– available health care;– communication; and– the level of advance planning.
25
WHO: A(H1N1)v — a ‘moderate’ pandemic
26
What is meant by 'moderate' and 'severe'? Not a simple scale What most people experience. Attributable risks? For most
people it’s a mild self-limiting disease. Death ratio. Expectation of an infected person dying (the Case
Fatality Ratio): < 0.5% of reported cases. Hospitalisation rate: Rates for children aged 0-23 months, 2-4
years, and 5-17 years were 1.1, 0.3, and 0.3 per 10,000, respectively. Rates for adults aged 18-49 years, 50-64 years, and >= 65 years were 0.1, 0.1, and 0.2 per 10,000, respectively.1
Pathogenicity markers and animal studies. No markers but ferret data indicate somewhat more severe than seasonal flu.
Number of people falling ill with respiratory illnesses at one time — 'winter pressures'. Pressure on the health services' ability to deal with these — very related to preparedness and robustness. Watch UK, Australia, Argentina, Chile, New Zealand.
Critical service functioning. Peak prevalence of people off ill or caring for others. Watch Australia, Chile, New Zealand.
1 http://www.cdc.gov/flu/weekly/: 2008-2009 Influenza Season Week 24 ending June 20, 2009
27
What is meant by 'moderate' and 'severe'? Not a simple scale Certain groups spared: older people. Certain individual dying unexpectedly, e.g.
children, pregnant women, young healthy adults. Public and media perception: low perception of
risk at present
Conclusion Not easy to come up with a single measure of
severity. May be better to state or agree what
interventions/countermeasures are useful and justifiable (and what are not).
http://www.who.int/csr/disease/swineflu/assess/disease_swineflu_assess_20090511/en/index.html and http://www.who.int/wer/2009/wer8422.pdf
28
Surveillance in a pandemic – future look
This will be crucial to detect– Changes in the behaviour of the virus– Discover who is really at risk
Will have to stop asking for numbers very soon Reliance on sentinel work – the previous EISS system
through TESSy Reporting of severe disease especially important for
informing the antiviral and vaccine priorities Special workshop 14-15 July in Stockholm
29
Conclusions
This pandemic will run through the rest of 2009-2010.
The first wave will probably start earlier than we might like.
While this looks like a ‘moderate’ pandemic - there will be surprises.
Europe is better prepared than many other regions and a lot better prepared than we were in 2005.
Final preparations will be very worthwhile. ECDC will be there to work with the
Commission, EMEA and WHO to give every support to Member States.
Thank you!