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INFLUENZA A (H1N1) - WORLDWIDE (68): SOUTHERN HEMISPHERE
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A ProMED-mail post
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ProMED-mail is a program of the
International Society for Infectious Diseases
<http://www.isid.org>
In this update:
[1] Brazil - new strain discounted
[2] Southern hemisphere activity
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[1] Brazil - new strain discounted
Date: Wed 17 Jun 2009
Source: CIDRAP News [edited]
<http://www.cidrap.umn.edu/cidrap/content/influenza/swineflu/news/jun1709flustrain.html>
The Centers for Disease Control and Prevention (CDC) and other
experts have rejected a report that a new strain of the novel [2009
swine-origin] H1N1 influenza virus has been identified in a Brazilian
patient.
Scientists at Adolfo Lutz Bacteriological Institute in Sao Paolo said
they found the new strain in a local patient who has recovered,
according to a Medical News Today (MNT) report, which was based on
information from the institute and Agence France-Presse [see also
ProMED-mail post: Influenza A (H1N1) - worldwide (66): new strain,
sequence analysis archive number 20090617.2235]. The story said the
scientists found "a number of discrete alterations in nucleotide and
amino acid sequences" in the isolate's hemagglutinin (HA) gene. They
also analyzed the matrix-protein (MP) gene and found no changes.
But CDC spokesman Joe Quimby in Atlanta discounted the report that
the isolate is a new strain. "Our scientists have no knowledge of a
new strain of novel A H1N1 influenza," he said. "It's the same
strain; it's not a new strain," Quimby added. The Brazilian
researchers labeled the isolate A/Sao/Paolo/1454/H1N1. They deposited
the nucleotide sequences for the HA and MP genes in GenBank under
accession numbers GQ247724 and GQ250156, the MNT report said.
Vincent Racaniello, a Columbia University virologist who writes
Virology Blog, also dismissed the claim of a new strain. "Comparison
of the amino acid sequence of the HA protein of A/Sao Paulo/1454/H1N1
with those of other isolates of the current pandemic strain reveals
no alterations in the HA protein which would allow the virus to
infect new hosts," Racaniello wrote in his blog. "The HA protein of
this virus and many other 2009 H1N1 isolates are identical. The few
amino acid differences with other 2009 H1N1 isolates are in areas
that would not be expected to influence antigenicity or host range."
The MNT report said the virus came from a 26-year-old Sao Paolo man
who fell ill shortly after returning from a trip to Mexico. He was
hospitalized on 24 Apr 2009 and later recovered.
[Byline: Robert Roos]
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Communicated by:
ProMED-mail <promed@promedmail.org>
******
[2] Southern hemisphere activity
Date: Thu 18 Jun 2009
Source: Eurosurveillance, Volume 14, Issue 24, 18 Jun 2009 [edited]
<http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19246>
Influenza A (H1N1) virus activity in the Southern Hemisphere -
Lessons to learn for Europe? By: E Depoortere, J Mantero, A Lenglet,
P Kreidl, D Coulombier. At: The European Centre for Disease
Prevention and Control, Stockholm, Sweden
--------------------------------------------
Outside the tropics, influenza infections show seasonal patterns
which depend on the latitude but appear not to be influenced by
longitude. The factors influencing this seasonality are not yet fully
understood, but indoor crowding, lower temperatures, decreased
humidity and reduced levels of sunlight are believed to influence
both transmission and host susceptibility [1]. Seasonal influenza
typically occurs between November and March in the northern
hemisphere, and between April and September in the southern
hemisphere. However, a temporal overlap of influenza activity between
both hemispheres has been described [2]. In tropical regions
influenza occurs year-round; it remains unclear whether tropical
regions serve as reservoir for the epidemics in both hemispheres.
During seasonal epidemics, dominant strains of influenza virus are
described that may vary within a hemisphere and in their impact on
morbidity. During the 2007-08 influenza season for example, the
dominant strain circulating in Europe was seasonal influenza A(H1N1),
whereas in the Americas influenza A(H3N2) was dominant [3,4].
Although they occur in distinct periods of the year, influenza
strains circulating in the 2 hemispheres are not independent of each
other. This is one of the reasons why the production of the seasonal
influenza includes virological information from the circulating
strains in both hemispheres. The recommendations for the composition
of seasonal influenza vaccines are published twice annually by the
World Health Organization before the start of the season in the
respective hemispheres, usually in February and September [5].
Considering the interaction of seasonal influenza activity between
the northern and southern hemisphere, we can expect the virus to
behave similarly in terms of attack rates, clinical spectrum of
illness and risk factors for severity. This gives an opportunity to
countries in the northern hemisphere to learn from experiences in the
southern hemisphere and prepare accordingly.
Current influenza situation in Chile and Australia
Large parts of Chile and Australia are located in the temperate area
of the southern hemisphere, with a defined influenza season and the
majority of cases occurring between May to September. Both countries
have an established seasonal influenza surveillance system [6,7].
Chile documents significant levels of influenza activity every 2 to 4
years, while Australia has reported a general increase in both
influenza-like illness and influenza laboratory notifications in
recent years.
In the past weeks, corresponding with the start of the influenza
season in the southern hemisphere, both countries experienced a steep
increase in reported cases of influenza A(H1N1) virus. Chile reported
its 1st cases in mid-May 2009: small clusters (consisting of between
2 and 6 cases) in different schools as well as 3 cases having
travelled back from the Dominican Republic. By the end of May 2009,
11 of the 15 administrative regions in the country had reported cases
[8]. On 12 Jun 2009, the total number of cases was 2335, including 2
deaths; the majority (66 percent) of infections occurred in persons
5-19 years of age, and 2 percent were considered severe, requiring
hospitalisation [9]. In Australia, the 1st case of A(H1N1)v was
confirmed on 8 May 2009, 3 weeks later all 8 jurisdictions of
Australia reported laboratory confirmed cases. By 16 Jun 2009,
Australia reported 1965 cases country-wide, of which 62 percent were
from Victoria [10].
Chile and Australia responded to the 1st cases of influenza A(H1N1)v
by implementing a "containment" strategy. Following the rapidly
evolving epidemiological situation, Chile changed to a "mitigation"
strategy by the end of May 2009 (2 weeks after the 1st case report).
Australia changed its strategy initially in the most affected state
of Victoria, where a modified "sustain" phase was implemented
[11,12]. On 17 Jun 2009, the country started moving into a new
"protect" phase, taking into account the less severe clinical
characteristics of the current pandemic [13]. This change in strategy
impacted among others the laboratory testing strategies, focusing
mainly on the early detection and adequate treatment of (potentially)
severe cases.
What lessons can we learn from the present situation in Chile and Australia?
As with seasonal influenza in the past years, the influenza A(H1N1)
virus situation in the winter period in the southern hemisphere is
likely to reveal what can be expected in the winter in the northern
hemisphere. Even if the season in the southern hemisphere has only
started and there are only limited data on the influenza A(H1N1)
virus situation available, some early conclusions can be drawn
already. However, it will be even more important for the northern
hemisphere countries, including those in Europe, to continue
monitoring the situation in the coming weeks closely, to gain further
knowledge on populations most affected, risk factors for developing
severe illness, changes in the virus' virulence, transmissibility,
and susceptibility to anti-viral drugs, as well as the impact of
pharmaceutical and non-pharmaceutical public health measures.
The current trend in the number of cases reported in Australia and
Chile, which are rapidly increasing and coinciding with the influenza
season, is different from what is being observed in Europe, where
progression still seems to be slower and/or delayed. In Europe,
influenza activity can be expected to remain on a low level during
the northern summer months, whereas a steep increase, as seen
currently in Australia and Chile, might be observed at the start of
the influenza season in Europe around September 2009. Both Chile and
Australia rapidly moved from containment to mitigation or sustaining
strategies.
The approach of the European Member States over the past few weeks
has been to implement intense containment measures, including active
case finding and tracing of contacts, isolation of cases and
contacts, and antiviral treatment and prophylaxis. These measures
were pertinent in reaction to the 1st appearance of the new virus in
Europe. However, it is unclear if these efforts will still be
sustainable in the coming winter season when the virus is likely to
be widely circulating on the continent. It can be expected that
countries will implement different measures depending on the national
epidemiological and virological situation.
What additional information is needed to be able to respond adequately?
Studies on the effectiveness of non-pharmaceutical public health
measures from the southern hemisphere will be important, even though
caution is recommended when comparing to countries with different
healthcare systems, population density and social structures. In
addition, the behaviour of other seasonal influenza viruses in terms
of co-circulation and predominance of one strain versus the other
will be closely monitored. In Chile, in week 21, 90 percent of the
circulating influenza virus detected was due to influenza A(H1N1)
virus, and in week 22 in the United States, the proportion was 89
percent [14,15]. The predominance of the pandemic strain over other
influenza strains is a phenomenon that has been observed in previous
pandemics [16]. If this will also become true for other southern
countries, the same can be expected in the northern hemisphere, and
public health measures, including vaccination and treatment, will
need to be adapted accordingly.
Since its detection in April this year [2009], a lot of information
on the epidemiology and virology of the new [2009 swine-origin]
influenza A(H1N1) virus has become available, mainly from Mexico and
the United States. However, this information reflected the initial
spread of the virus, which may not be representative for the coming
winter season. Hence, monitoring the situation in the southern winter
period will help to better anticipate, and therefore prepare, for the
northern winter and its influenza season. However, some of the
findings might need careful interpretation and cannot necessarily be
generalised for Europe. International efforts should aim at
supporting countries in the southern hemisphere in their response to
the pandemic, resulting in a mutual benefit: Additional resources for
the south, allowing in-depth and targeted investigations, and
increased epidemiological understanding for the north, allowing
better preparedness for the expected winter peak.
References:
[1] Nguyen-Van-Tam B-J. Epidemiology of Influenza. In: KG Nicholson
RW, AJ Hay, ed. Textbook of Influenza. Malden: Blackwell Science
1998:181-206.
[2] Finkelman BS, Viboud C, Koelle K, Ferrari MJ, Bharti N, Grenfell
BT. Global patterns in seasonal activity of influenza A/H3N2, A/H1N1,
and B from 1997 to 2005: viral coexistence and latitudinal gradients.
PloS One. 2007;2(12):e1296.
[3] Centers for Disease Control and Prevention (CDC). Influenza
Activity - United States and worldwide, 2007-08 season. MMWR Morb
Mortal Wkly Rep. 2008;57(25):692-7.
[4] Lackenby A, Hungnes O, Dudman SG, Meijer A, Paget WJ, Hay AJ, et
al. Emergence of resistance to oseltamivir among influenza A(H1N1)
viruses in Europe. Euro Surveill. 2008;13(5):pii=8026. Available from:
<http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=8026>.
[5] World Health Organization (WHO). Recommendations for Influenza
Vaccine Composition. Northern hemisphere, 2007-2008. Available from:
<http://www.who.int/csr/disease/influenza/vaccinerecommendations1/en/>.
[6] Australian Government. Department of Health and Ageing.
Communicable Diseases Intelligence (CDI). Surveillance systems
reported in CDI, 2008. CDI. 2008;32(1).
[7] Chile Ministry of Health. Vigilancia de Influenza: Informe
situacion 2008. [Surveillance of influenza: situation report 2008].
[In Spanish]. [Accessed 17 Jun 2009]. Available from:
<http://epi.minsal.cl/epi/html/bolets/reportes/Influenza/InfluenzaAnual2008.pdf>.
[8] Chile Ministry of Health. Informes diarios de prensa sobre
Influenza A (H1N1) en Chile, Mayo-Junio 2009 [Daily situation
updates, 26 Apr 2009 May-5 Jun 2009]. [In Spanish]. [Accessed 17 Jun
2009]. Available from:
<http://www.pandemia.cl/>.
[9] Chile Ministry of Health. Informe situacion de infeccion por
nueva influenza A(H1N1) en Chile al 11 de Junio de 2009. [Situation
report for the new influenza A (H1N1) in Chile on 11 Jun 2009]. [In
Spanish]. [Accessed 17 Jun 2009]. Available from:
<http://www.pandemia.cl/pagnew/prensa/REPORTE_12_06_09.pdf>.
[10] Australian Government, Department of Health and Ageing. National
tally of confirmed cases of H1N1 influenza 09, as at 5 pm, 6 Jun
2009. [Accessed 17 Jun 2009]. Available from:
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/3C952C84F7A3AE5BCA2575CE006F0F48/$File/H1N1%20Influenza%2009%2012pm%2010%20June.pdf>.
[11] Australian Government. Department of Health and Ageing. Previous
advice from the Chief Medical Officer. 9 Jun 2009. [Cited 12 Jun
2009]. Available from:
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/prev-adv-cmo>.
[12] Chile Ministry of Health. Guia clinica para el manejo de casos
Nueva Influenza Humana A (H1N1) (IHA H1N1). Etapa de Mitigacion.
Fecha: 09-06-09.
[Clinical guideline for case management: New Human Influenza A (H1N1)
(IHA H1N1): Mitigation phase. 9 Jun 2009.]. [In Spanish]. [Accessed
17 Jun 2009]. Available from:
<http://www.pandemia.cl/pagnew/profsalud/Guia_clinica_Manejo_de_caso.pdf>.
[13] Australian Government. Department of Health and Ageing. New
pandemic phase "protect." [Accessed 17 Jun 2009]. Available from:
<http://www.healthemergency.gov.au/internet/healthemergency/publishing.nsf/Content/news-170609>.
[14] Centers for Disease Control and Prevention (CDC). 2008-2009
Influenza Season Week 22 ending Jun\ 6, 2009. CDC 12 Jun 2009.
Available from:
<http://www.cdc.gov/flu/weekly/>.
[15] Chile Ministry of Health. Nueva Influenza A-H1N1: Proximo lunes
comienza etapa de mitigacion [New influenza A(H1N1): the mitigation
phase starts next Monday]. [In Spanish]. 27 May 2009. Available from:
<http://www.redsalud.gov.cl/noticias/noticias.php?id_n=445&show=5-2009>.
[16] Taubenberger JK Morens DM. 1918 influenza: the mother of all
pandemics. Emerg Infect Dis. 2006; 12(1):15-22.
--
Communicated by:
ProMED-mail <promed@promedmail.org>
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Influenza A (H1N1) - worldwide (53): case counts 20090531.2025
Influenza A (H1N1) - worldwide (52): seasonal vaccine 20090530.2010
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