Giuseppe
Emeritus
Swine Origin Influenza A(H3N2), Recent Updates from the World Health Organization
About the situation regarding the most recent sporadic human infections with swine origin influenza virus A(H3N2) in USA, WHO released several updates in different documents:
To note the fact that WHO - despite the reassurance that A(H3N2) of swine origin has some cross reactions with seasonal human influenza viruses A(H3N2) ciruclating in the 1990 decade - it is preparing a seeds for a possible human vaccine development. (IOH)
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Source: World Health Organization, full PDF document: (LINK), full text: (LINK).
Antigenic and genetic characteristics of zoonotic influenza viruses and development of candidate vaccine viruses for pandemic preparedness - September 2011
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Swine-Origin Influenza A(H3N2)
Swine influenza A(H3N2) viruses are enzootic in swine herds of North America and other parts of the world. Characterisation of recent A(H3N2) viruses from swine in North America indicates that their HA genes have evolved from the human virus precursors that circulated in the mid-1990s. Isolation of swine-origin influenza viruses (SOIV) A(H3N2) from humans has been reported infrequently. The United States of America reported eight infections due to A(H3N2) SOIV between January 2005 and 15 February 2011.
A(H3N2) SOIV infections from 16 February 2011 to 19 September 2011
There have been four human infections with A(H3N2) SOIV in the states of Indiana (1) and Pennsylvania (3), United States of America, in this period. The HA and neuraminidase genes of these four viruses were similar to those of swine viruses that circulate in the United States of America. Sequencing data indicated that the matrix genes of these viruses were acquired from an A(H1N1)pdm09 virus, unlike SOIV isolates from previous human cases. Antigenic analysis indicated that these viruses were distinct from currently circulating human A(H3N2) viruses but similar to swine A(H3N2) viruses from previous years as well as to A/Minnesota/11/2010 (H3N2) SOIV (Table 7), from which a candidate vaccine virus is under development.
As the viruses continue to evolve new SOIV candidate vaccine viruses will be developed and announced as they become available. Institutions, companies and others who wish to receive these candidate vaccine viruses should contact WHO at gisrs-whohq@who.int or the institutions listed in announcements published on the WHO website (4).
Table 7. Antigenic properties of a recent A(H3N2) SOIV
[Reference ferret antisera - CA/09 - SD/03 - Perth/09 - Sw/IL/09 - KS/09 - PA/10 - WI/10 - MN/10]
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Source: World Health Organization, full PDF document (LINK), full text: (LINK).
Recommended composition of influenza virus vaccines for use in the 2012 southern hemisphere influenza season - September 2011
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Zoonotic influenza infections caused by avian A(H5N1), avian A(H9N2) and swine A(H3N2) viruses
From 16 February 2011 to 19 September 2011, 45 confirmed human cases of A(H5N1), 24 of which were fatal, were reported by Bangladesh, Cambodia, Egypt and Indonesia, countries in which highly pathogenic avian influenza A(H5N1) is present in poultry. Since December 2003, a total of 564 cases with 330 deaths have been confirmed in 15 countries. To date there has been no evidence of sustained human-to-human transmission.
One human case of influenza A(H9N2) was detected in Bangladesh and four human infections caused by swine A(H3N2) viruses were detected in the United States of America during the same period.
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Source: World Health Organization, full PDF document: (LINK), full text: (LINK).
Influenza at the human-animal interface - Summary and assessment as of 5 September 2011
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Human infections with other animal influenza viruses
The United States of America (USA) reported two human cases of swine influenza A (H3N2) infection, one in Pennsylvania and one in Indiana (3). The virus is similar to one that has been circulating in swine in the USA since 1998 and which has been previously identified in eight human cases, but it contains one gene segment, the M gene, derived from the pandemic influenza A (H1N1) virus. This virus appears to have some antigenic crossreactivity with human seasonal H3N2 viruses circulating in the 1990s. The Indiana case did not have direct exposure to pigs but had contact with a care-giver who did have recent contact. The three cases in Pennsylvania had all recently visited a fair where pigs were present.
Reassortments of the 2009 influenza A (H1N1) virus with other swine influenza A viruses have been reported previously in swine (4). The virus does not appear to have spread widely in humans.
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About the situation regarding the most recent sporadic human infections with swine origin influenza virus A(H3N2) in USA, WHO released several updates in different documents:
- Antigenic and genetic characteristics of zoonotic influenza viruses and development of candidate vaccine viruses for pandemic preparedness - September 2011
- Recommended composition of influenza virus vaccines for use in the 2012 southern hemisphere influenza season - September 2011
- Influenza at the human-animal interface - Summary and assessment as of 5 September 2011
To note the fact that WHO - despite the reassurance that A(H3N2) of swine origin has some cross reactions with seasonal human influenza viruses A(H3N2) ciruclating in the 1990 decade - it is preparing a seeds for a possible human vaccine development. (IOH)
-
-----
-
Source: World Health Organization, full PDF document: (LINK), full text: (LINK).
Antigenic and genetic characteristics of zoonotic influenza viruses and development of candidate vaccine viruses for pandemic preparedness - September 2011
(...)
Swine-Origin Influenza A(H3N2)
Swine influenza A(H3N2) viruses are enzootic in swine herds of North America and other parts of the world. Characterisation of recent A(H3N2) viruses from swine in North America indicates that their HA genes have evolved from the human virus precursors that circulated in the mid-1990s. Isolation of swine-origin influenza viruses (SOIV) A(H3N2) from humans has been reported infrequently. The United States of America reported eight infections due to A(H3N2) SOIV between January 2005 and 15 February 2011.
A(H3N2) SOIV infections from 16 February 2011 to 19 September 2011
There have been four human infections with A(H3N2) SOIV in the states of Indiana (1) and Pennsylvania (3), United States of America, in this period. The HA and neuraminidase genes of these four viruses were similar to those of swine viruses that circulate in the United States of America. Sequencing data indicated that the matrix genes of these viruses were acquired from an A(H1N1)pdm09 virus, unlike SOIV isolates from previous human cases. Antigenic analysis indicated that these viruses were distinct from currently circulating human A(H3N2) viruses but similar to swine A(H3N2) viruses from previous years as well as to A/Minnesota/11/2010 (H3N2) SOIV (Table 7), from which a candidate vaccine virus is under development.
As the viruses continue to evolve new SOIV candidate vaccine viruses will be developed and announced as they become available. Institutions, companies and others who wish to receive these candidate vaccine viruses should contact WHO at gisrs-whohq@who.int or the institutions listed in announcements published on the WHO website (4).
Table 7. Antigenic properties of a recent A(H3N2) SOIV
[Reference ferret antisera - CA/09 - SD/03 - Perth/09 - Sw/IL/09 - KS/09 - PA/10 - WI/10 - MN/10]
- Reference antigens
- A/California/07/2009 H1N1pdm09 - 2560 - 2560 - <10 - 20 - <10 - 40 - <10 ? <10
- A/South Dakota/03/2008 Human H1N1-SOIV - 2560 - 5120 - 10 - 160 - 160 - 160 - <10 - <10
- A/Perth/16/2009 Seasonal H3N2 - <10 - <10 - 640 - <10 - <10 - <10 - <10 - <10
- A/swine/Illinois/02907/2009 Swine H3N2 - <10 - <10 - <10 - 2560 - 2560 - 320 - 160 - 80
- A/Kansas/13/2009 Human H3N2-SOIV - <10 - <10 - <10 - 1280 - 2560 - 320 - 160 - 80
- A/Pennsylvania/14/2010 Human H3N2-SOIV - <10 - <10 - 10 - 160 - 320 - 1280 - 320 - 640
- A/Wisconsin/12/2010 Human H3N2-SOIV - <10 - <10 - <10 - 160 - 80 - 640 - 1280 ? 640
- A/Minnesota/11/2010 Human H3N2-SOIV - <10 - <10 - <10 - 40 - 40 - 320 - 320 - 1280
- Test antigens
- A/Indiana/08/2011 - 20 - <10 - 10 - 40 - 80 - 1280 - 1280 - 1280
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Source: World Health Organization, full PDF document (LINK), full text: (LINK).
Recommended composition of influenza virus vaccines for use in the 2012 southern hemisphere influenza season - September 2011
(...)
Zoonotic influenza infections caused by avian A(H5N1), avian A(H9N2) and swine A(H3N2) viruses
From 16 February 2011 to 19 September 2011, 45 confirmed human cases of A(H5N1), 24 of which were fatal, were reported by Bangladesh, Cambodia, Egypt and Indonesia, countries in which highly pathogenic avian influenza A(H5N1) is present in poultry. Since December 2003, a total of 564 cases with 330 deaths have been confirmed in 15 countries. To date there has been no evidence of sustained human-to-human transmission.
One human case of influenza A(H9N2) was detected in Bangladesh and four human infections caused by swine A(H3N2) viruses were detected in the United States of America during the same period.
(...)
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Source: World Health Organization, full PDF document: (LINK), full text: (LINK).
Influenza at the human-animal interface - Summary and assessment as of 5 September 2011
(...)
Human infections with other animal influenza viruses
The United States of America (USA) reported two human cases of swine influenza A (H3N2) infection, one in Pennsylvania and one in Indiana (3). The virus is similar to one that has been circulating in swine in the USA since 1998 and which has been previously identified in eight human cases, but it contains one gene segment, the M gene, derived from the pandemic influenza A (H1N1) virus. This virus appears to have some antigenic crossreactivity with human seasonal H3N2 viruses circulating in the 1990s. The Indiana case did not have direct exposure to pigs but had contact with a care-giver who did have recent contact. The three cases in Pennsylvania had all recently visited a fair where pigs were present.
Reassortments of the 2009 influenza A (H1N1) virus with other swine influenza A viruses have been reported previously in swine (4). The virus does not appear to have spread widely in humans.
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