Published Date: 2009-05-11 18:00:06
Subject: PRO/AH/EDR> Influenza A (H1N1) - worldwide (23)
Archive Number: 20090511.1764
INFLUENZA A (H1N1) - WORLDWIDE (23)
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In this update:
[1] Outbreak analysis
[2] UK perspective
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[1] Outbreak analysis
Date: Mon 11 May 2009
Source: Science Express [edited]
<http://www.sciencemag.org/cgi/content/abstract/1176062>
Pandemic Potential of a Strain of Influenza A (H1N1): Early Findings By:
Christophe Fraser 1, Christl A. Donnelly 1, Simon Cauchemez 1, William P.
Hanage 1, Maria D. Van Kerkhove 1, T. Deirdre Hollingsworth 1, Jamie
Griffin 1, Rebecca F. Baggaley 1, Helen E. Jenkins 1, Emily J. Lyons 1,
Thibaut Jombart 1, Wes R. Hinsley 1, Nicholas C. Grassly 1, Francois
Balloux 1, Azra C. Ghani 1, Neil M. Ferguson 1*, Andrew Rambaut 2, Oliver
G. Pybus 3, Hugo Lopez-Gatell 4, Celia M Apluche-Aranda 5, Ietza Bojorquez
Chapela 4, Ethel Palacios Zavala 4, Dulce Ma. Espejo Guevara 6, Francesco
Checchi 7, Erika Garcia 7, Stephane Hugonnet 7, Cathy Roth 7. The WHO Rapid
Pandemic Assessment Collaboration (All authors are members of this
collaboration. Correspondence to Neil M. Ferguson
<neil.ferguson@imperial.ac.uk >). 1 MRC Centre for Outbreak Analysis &
Modelling, Department of Infectious Disease Epidemiology, Imperial College
London, Faculty of Medicine, Norfolk Place, London W2 1PG, UK. 2 Institute
of Evolutionary Biology, University of Edinburgh, Ashworth Laboratories
Edinburgh EH9 3JT, UK. 3 Department of Zoology, University of Oxford, South
Parks Road, Oxford OX1 3PS, UK. 4 Directorate General of Epidemiology, FCO.
De P. Miranda 177 5th Floor, Mexico City, 01480, Mexico. 5 National
Institute of Epidemiological Diagnosis and Reference, Prolongacion Carpio
No. 470 (3 piso), Col Santo Tomas, Mexico City, C.P. 11340, Mexico. 6
Secretaria de Salud - Servicios de Salud de Veracruz Soconusco No. 36
Colonia Aguacatal C.P. 910 Xalapa, Veracruz, Mexico State. 7 World Health
Organization, 20 Av. Appia, 1211 Geneva, Switzerland.
A novel influenza A (H1N1) virus has spread rapidly across the globe.
Judging its pandemic potential is difficult with limited data but
nevertheless is essential to inform appropriate health responses. By
analyzing the outbreak in Mexico, early data on international spread, and
viral genetic diversity, we make an early assessment of transmissibility
and severity. Our estimates suggest that 23 000 (range 6000-32 000)
individuals had been infected in Mexico by late April 2009, giving an
estimated case fatality ratio (CFR) of 0.4 per cent (range 0.3 to 1.5 per
cent) based on confirmed and suspect deaths reported up to that time. In a
community outbreak in the small community of La Gloria, Veracruz, no deaths
were attributed to infection, giving an upper 95 per cent bound on CFR of
0.6 per cent. Thus, while substantial uncertainty remains, clinical
severity appears less than that seen in 1918 but comparable with that seen
in 1957. Clinical attack rates in children in La Gloria were twice those in
adults (less than 15 years of age: 61 per cent, 15: 29 per cent). Three
different epidemiological analyses gave R0 estimates in the range 1.4-1.6,
while a genetic analysis gave a central estimate of 1.2. This range of
values is consistent with 14 to 73 generations of human-to-human
transmission having occurred in Mexico to late April 2009. Transmissibility
is therefore substantially higher than seasonal flu and comparable with
lower estimates of R0 obtained from previous influenza pandemics.
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[2] UK perspective
Date: Mon 11 May 2009
Source: BBC-News [edited]
<http://news.bbc.co.uk/1/hi/health/8044299.stm>
Ten new cases of swine flu have been confirmed in England, taking the total
number in the UK to 65, the Health Protection Agency has said. Another 7
adults and 3 children have been diagnosed with the virus. The news comes as
a UK analysis concludes that the World Health Organization was right to
raise the alert over a potential global flu pandemic. It says the latest
outbreak is likely to be comparable to the pandemics of the 20th century.
The study, led by Professor Neil Ferguson, of Imperial College, London, is
published in the leading journal Science [see preceding report]. It finds
that -- as suspected -- the virus is more infectious than normal. Seasonal
flu normally infects one in 10 of the population. So far, swine flu has
infected 1/3rd of the people that have come into contact with it in Mexico.
However, Professor Ferguson admitted it was difficult to quantify the
impact on human health at this stage. His study suggests that swine flu
could kill between 4 in every 1000 infected people and 14 in every 1000.
Professor Ferguson said: "The World Health Organization was correct in its
judgment that this is a virus that should not be ignored, but these figures
suggest at this stage it is not going to be catastrophic."
Of the new cases in England, 4 are in eastern England, and 3 are in the
north west. Three more are in London, including a pupil at Hampton School
in south west London. The school has been closed for a week from Monday [11
May 2009] as a precaution. Four other schools in England have reopened.
Hampton School, which is an independent boys' secondary, shut its doors
after a Year 7 pupil fell ill after traveling overseas. The school said the
boy was recovering well at home, and GCSE and A level exams, the bulk of
which commence this week, would continue as planned. It is offering
antiviral drugs to all children in Year 7, any staff who had close contact
with the pupil, and any other children who shared school coach journeys
with him. These include some girls from the nearby Lady Eleanor Holles
School in Hampton.
A Department of Health spokesman said on Monday [11 May 2009] that all
infections in the UK so far had been "mild". Thanks to early diagnosis and
treatment with antivirals, the spread of the virus is being limited and
symptoms reduced. "But it is right to prepare for the possibility of a
global pandemic. The UK's arrangements are continuing to ensure that we are
well-placed to deal with this new infection." The 2 cases in London are
both connected with Alleyn's School in Dulwich, which was closed on 4 May
2009 after 5 pupils were confirmed with the virus. NHS London said the 2
latest cases were a 12 year old pupil and a parent. Despite the
development, the school reopened on Monday [11 May 2009], and the Health
Protection Agency stressed that because of the time taken to diagnose swine
flu, all 10 newly-confirmed patients may already have recovered and may be
symptom-free. NHS East of England said the 4 cases in its area included a
man from North Weald, Essex who had close contact with an already confirmed
case and a child from Canvey Island, also in Essex, who recently visited
Mexico. Another case involved a man from Lowestoft, Suffolk, who recently
visited Florida, and the 4th was a woman from the Huntingdonshire district
in Cambridgeshire. Investigations are continuing into the origin of her
infection. In the north west, 2 of those infected are adults who have
returned from abroad, and the 3rd adult is a case of close contact.
Meanwhile, holiday companies Thomson and First Choice said they were
cancelling all flights to the Mexican resorts of Cancun and Cozumel up to
and including 18 May 2009. They also said that their last holiday makers
still in Mexico would be returning home on Monday [11 May 2009].
--
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See Also
Influenza A (H1N1) - worldwide (22): case counts 20090511.1759Influenza A (H1N1) - worldwide (21) 20090510.1749
Influenza A (H1N1) - worldwide (20): case counts 20090510.1741
Influenza A (H1N1) - worldwide (19) 20090509.1733
Influenza A (H1N1) - worldwide (18): case counts 20090509.1728
Influenza A (H1N1) - worldwide (17) 20090508.1722
Influenza A (H1N1) - worldwide (16): case counts 20090507.1715
Influenza A (H1N1) - worldwide (15) 20090507.1709
Influenza A (H1N1) - worldwide (14): case counts 20090507.1702
Influenza A (H1N1) - worldwide (13) 20090506.1695
Influenza A (H1N1) - worldwide (12): case counts 20090505.1681
Influenza A (H1N1) - worldwide (11): coincident H3N2 variation 20090505.1679
Influenza A (H1N1) - worldwide (10): case counts 20090504.1675
Influenza A (H1N1) - worldwide (09) 20090504.1673
Influenza A (H1N1) - worldwide (08): case counts 20090503.1660
Influenza A (H1N1) - worldwide (07) 20090503.1658
Influenza A (H1N1) - worldwide (06): case counts 20090502.1654
Influenza A (H1N1) - worldwide (05) 20090503.1657
Influenza A (H1N1) - worldwide (04): case counts 20090501.1648
Influenza A (H1N1) - worldwide (03) 20090501.1646
Influenza A (H1N1) - worldwide (02): case counts 20090430.1638
Influenza A (H1N1) - worldwide 20090430.1636
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