World Health Organization, Influenza Update, United Kingdom (regarding severe cases virus isolates antigenicity and genetics), Dec. 20 2010 (extract)

[Giuseppe]

Source: World Health Organization, full text: http://www.who.int/csr/disease/influenza/2010_12_17_GIP_surveillance/en/index.html

Influenza update - 17 December 2010

(...)

In the United Kingdom, the winter influenza epidemic is under way, particularly across England.

Since mid to late November 2010 there have reports of increasing numbers of community outbreaks of influenza (due to both influenza H1N1 (2009) and B viruses), increasing proportions of sentinel respiratory specimens testing positive for influenza (56% in England during the second week of December; of which 67% were H1N1 (2009) and 33% were influenza B viruses), and increasing numbers of severe influenza cases requiring intensive care.

Available data indicate that the currently circulating strain of the H1N1 (2009) virus in the UK is epidemiologically and virologically similar to that observed last year during the influenza H1N1 2009 pandemic.

All influenza viruses characterized to date have been found to be similar to the strains currently included in the seasonal influenza trivalent vaccine. (see below in Virologic Surveillance for details on the characterization of the virus)

It is too early to tell what the overall impact of the current epidemic will be in the UK in comparison to the 2009 season.

(...)

Outbreaks of influenza A H1N1 (2009) and influenza B viruses in the United Kingdom.

A number of severe and fatal cases of influenza A H1N1 (2009) and influenza B have recently been reported by the United Kingdom.

* Influenza A H1N1 (2009) viruses characterised to date, in samples from the community, hospitalised patients and fatal cases in the United Kingdom, are antigenically homogeneous and similar to the vaccine virus A/California/7/2009.

* Genetically these H1N1 (2009) viruses have several amino acid substitutions relative to the vaccine virus but these do not affect the antigenicity of the virus and have also been seen in viruses from other parts of the world.

* The B viruses analysed in the United Kingdom to date are B/Victoria/2/87 lineage viruses and are antigenetically and genetically closely related to the B/Brisbane/60/2008 vaccine virus.

(...)

-
-----