[Source: World Health Organization, full PDF document: (LINK). Edited.]
Influenza at the human-animal interface - Summary and assessment as of 4 June 2012
Human infections with avian influenza A(H5N1) virus and associated animal health events
From 2003 through 04 June 2012, 605 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries, of which 357 died. Since January 2012, 27 human cases of influenza A(H5N1) virus infection have been reported to the WHO.
Between 7 May and 4 June 2012, 2 new human cases have been reported from Cambodia (1) and China(1)
According to FAO, H5N1 viruses are thought to be circulating endemically in poultry in China, Egypt, Indonesia, Viet Nam, Bangladesh and India. In Cambodia, sporadic reintroduction into poultry populations is thought to occur1. The epidemiologic curve of recent human cases (Figure 1) follows the same pattern seen in previous years, with larger numbers of cases in the winter months, decreasing towards summer in the northern hemisphere. This curve follows the seasonal curve of outbreaks in birds.
The 2 new cases were sporadic cases. No further cases linked to the confirmed cases were reported.
Both had exposure history (see Table 1). The H5N1 virus isolated from the specimen of the case in China belongs to the clade 18.104.22.168, which clusters with the viruses recently isolated from wild birds in China, Hong Kong Special Administrative Region (SAR), and from the human case detected in December 2010.
Clade 22.214.171.124 is the predominant clade currently circulating in birds in the region2. No further virological information regarding the Cambodian case is yet available to WHO.
Table 1: laboratory-confirmed human cases of avian influenza A(H5N1) virus infection (5 March -2 April 2012)
[Country – Province – Age (y) – Sex - Date of onset - Date of Hospitalisation – Oseltamivir treatment Start date - Date of death - Exposure to]
- Cambodia – Kampong Speu Province – 10 – F – 20/05/2012 (28/03/2012) - 25/05/2012 – NA – (30/03/2012) - 27/05/2012 - Sick/ dead poultry
- China - Hong Kong SAR* – 2 – M - 23/05/2012 - 28/05/2012 – NA - Live animal market in Guangdong
NA: not applicable or not available
*Case travelled from Guangdong province to Hong Kong SAR seeking health care
Overall public health risk assessment:
A decrease in reported events in poultry is expected for this time of year. Two sporadic cases reported this month in countries with known influenza A(H5N1) circulation in poultry are within the expected range. These sporadic cases do not appear to have features that would raise concern regarding onward sustained human to human transmission.
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 (www.oie.int/animal-health-in-the-world/web-portal-onavian-influenza/ ), FAO (www.fao.org/avianflu/en/index.html ), and OFFLU (http://www.offlu.net/index.html ).
- 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: www.oie.int/animal-health-in-the-world/web-portal-on-avian-influenza/
- Food and Agriculture Organization of the UN (FAO) webpage: Avian Influenza: 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
(1) Approaches to Controlling, Preventing and Eliminating H5N1 Highly Pathogenic Avian Influenza in Endemic Countries. Rome, United Nations Food and Agriculture Organization, 2011
(2) Antigenic and genetic characteristics of zoonotic influenza viruses and development of candidate vaccine viruses for pandemic preparedness Feb 2012 http://www.who.int/influenza/vaccines/virus/characteristics_virus_vaccines/en/index.html