Published Date: 2012-10-11
Date: Mon 1 Oct 2012
Source: WHO, Programmes and Projects [edited]
http://www.who.int/influenza/human_animal_interface/HAI_Risk_Assessment/en/index.html
A. Human infection with avian influenza A(H5N1) virus and associated animal health events:
-----------------------------------------------------
From
2003 through 1 Oct 2012, 608 laboratory-confirmed human cases with
avian influenza A(H5N1) virus infection have been officially reported to
WHO from 15 countries, of which 359 died. Since January 2012, 30 human
cases of influenza A(H5N1) virus infection have been reported to WHO.
Since the last update [10 Sep 2012], no new laboratory-confirmed human
cases with influenza A(H5N1) virus infection have been reported to WHO.
Public health risk assessment for avian influenza A(H5N1) viruses: The
public health risk for the virus remains unchanged.
B. Human infection with other non-human influenza viruses
---------------------------------------------------------
A(H3N2) variant virus infection
-------------------------------
The
United States of America (USA) reported few additional human cases of
influenza A(H3N2)v, and no additional deaths. The large majority of
cases have been associated with swine exposure, though instances of
likely human-to-human transmission have been identified. No sustained
human-to-human transmission has been reported.
Limited
serological studies [1-4] indicate that adults may have some
pre-existing immunity to this virus but children do not. Seasonal
vaccines do not provide cross protection against A (H3N2)v infection.
WHO has identified several candidate vaccine viruses specific for
A(H3N2)v that could be used to produce an (H3N2)v vaccine if needed [5].
Overall public health risk assessment for influenza A(H3N2)v viruses:
Further
human cases and small clusters may be expected as this virus is
circulating in the swine population in the USA and people may continue
to be exposed, especially through the autumn. Close monitoring of the
situation is warranted as schools have started again and changing
weather conditions may favor influenza transmission.
A(H1N1) variant virus infections
--------------------------------
As
a result of enhanced surveillance around the agricultural fairs, a case
of human infection with H1N1 variant influenza virus was detected and
reported from the USA [6]. The case occurred in August 2012 in a
previously healthy woman. She was not hospitalized and recovered from
her illness. The person had direct contact with swine at a State Fair.
No further cases were identified. This is the 2nd case of infection with
this H1N1v virus in the USA; the previous case occurred in 2011.
Canada
also reported a case of human infection with influenza A(H1N1)v in an
adult male with underlying risk factors. He developed symptoms at the
end of August [2012] and was hospitalized with pneumonia in September.
He had occupational exposure to swine. No additional cases have been
reported.
The influenza A(H1N1)v viruses isolated from
patients in the USA and Canada have an haemagglutinin similar to human
seasonal influenza viruses circulating very recently in people, which
might suggest some existing population immunity except in young
children. Current seasonal vaccines would provide cross protection
against these viruses. Available data indicates that the virus would be
susceptible to antivirals (neuraminidase inhibitors; oseltamivir and
zanamivir).
Overall public health risk assessment for influenza A(H1N1)v viruses:
Further
human cases and small clusters of human infection with these viruses
may be expected as they are circulating in swine populations. No
human-to-human transmission with this virus has been reported. It is
expected that the human populations are largely protected by existing
immunity except for young children and by the seasonal influenza
vaccine.
Because influenza viruses evolve constantly and
change characteristics and behavior unpredictably, WHO continues to
stress the importance of global monitoring of variant influenza viruses
and recommends to all Member States to strengthen routine surveillance
activities.
All human infections with non-human influenza
viruses as such are reportable to WHO under IHR (2005). More
information on influenza at the human-animal interface is available from
WHO (http://www.who.int/influenza/human_animal_interface/en/); additional information on influenza in animals is available from OIE (http://www.oie.int/animal-health-in-the-world/web-portal-on-avian-influenza/) and FAO (http://www.fao.org/avianflu/en/index.html), and OFFLU (http://www.offlu.net).
References
----------
1.
CDC. Antibodies cross-reactive to influenza A(H3N2) variant virus and
impact of 2010-11 seasonal influenza vaccine on cross-reactive
antibodies -- United States. MMWR 2012; 61(14): 237-41; [available at http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6114a1.htm].
2.
Skowronski, et al. Cross-reactive antibody to swine influenza
A(H3N2)subtype virus in children and adults before and after
immunisation with 2010/11 trivalent inactivated influenza vaccine in
Canada, August to November 2010. Euro Surveillance 2012; 17(4);
available at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20066.
3.
Waalen et al. Age-dependent prevalence of antibodies cross-reactive to
the influenza A(H3N2) variant virus in sera collected in Norway in 2011;
Euro Surveillance 2012; 17(19); available at http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=20170.
4.
Danuta Skowronski, et al. Cross-reactive and vaccine-induced antibody
to emerging swine influenza A(H3N2)v, JID 2012; available at http://jid.oxfordjournals.org/content/early/2012/08/07/infdis.jis500.full.pdf+html.
5. WHO. Candidate vaccine viruses for variant influenza A(H3N2); available at http://www.who.int/influenza/vaccines/virus/candidates_reagents/variant_a_h3n2/en/index.html.
6. CDC. H1N2 variant virus detected in Minnesota; available at http://www.cdc.gov/flu/spotlights/h1n2v-cases-mn.htm.
Relevant links
--------------
- WHO table: cumulative number of confirmed human cases of avian influenza A/(H5N1) reported to WHO: http://www.who.int/influenza/human_animal_interface/EN_GIP_LatestCumulativeNumberH5N1cases.pdf
- WHO table: H5N1 avian influenza: timeline of major events http://www.who.int/influenza/human_animal_interface/avian_influenza/H5N1_avian_influenza_update.pdf
- WHO archive: avian influenza situation updates: http://www.who.int/influenza/human_animal_interface/avian_influenza/archive/en/index.html
- World Organisation of Animal Health (OIE) webpage: web portal on avian influenza: http://www.oie.int/animal-health-in-the-world/web-portal-on-avian-influenza/
- Food and Agriculture Organization of the UN (FAO) webpage: avian influenza: http://www.fao.org/avianflu/en/index.html
- Updated unified nomenclature system for the highly pathogenic H5N1 avian influenza viruses: http://www.who.int/influenza/gisrs_laboratory/h5n1_nomenclature/en/index.html
--
communicated by:
ProMED-mail rapporteur Marianne Hopp
[This
document includes an epidemiological curve of avian influenza H5N1
cases in humans by country and month of onset, and a useful map of avian
influenza H5N1 cases in humans for 2012. Readers are recommended to
view these illustrations, which can be accessed, via the source URL
above. - Mod.CP]
[all editing is mine]
http://www.promedmail.org/direct.php?id=20121011.1337739
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