14 Mar 2013

Influenza at the human-animal interface - Summary and assessment as of 12 March 2013 (WHO, edited)

[Source: World Health Organization, full PDF document: (LINK). Edited.]

Influenza at the human-animal interface - Summary and assessment as of 12 March 2013

 

Human infection with avian influenza A(H5N1) viruses and associated animal health events

From 2003 through 12 March 2013, 622 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries, of which 371 died.

Since the last update on 15 February 2013, 2 new fatal laboratory-confirmed human cases with influenza A(H5N1) virus infection were reported to WHO from Cambodia.

China reported 2 deaths in the human cases previously reported (http://www.who.int/influenza/human_animal_interface/HAI_Risk_Assessment/en/index.html ).

Since the beginning of 2013, Cambodia reported nine human cases with influenza A(H5N1) virus infection including eight fatal cases. These cases come from five provinces all located in southern Cambodia. These cases do not seem to be linked epidemiologically, and most had contact with sick poultry in their villages.

The clade 1.1 viruses that have been isolated from cases are very similar to those isolated from poultry in the region.

Investigations around these cases did not detect additional cases.

This evidence suggests sporadic infections from exposure to infected poultry or contaminated environments, rather than human-to-human transmission.

It has been suggested that the A(H5N1) virus is circulating endemically in poultry in Cambodia(1) , as such, additional sporadic human cases might be expected.

 

Table 1: laboratory-confirmed human cases of avian influenza A(H5N1) virus infection (13 February- 12 March 2013)

[Country - Province - Age (y) - Sex - Date of onset - Date of Hospitalisation - Oseltamivir treatment Start date - Date of death - Exposure to]

  • Cambodia - Kampot - 20 months - M - 6/2/2013 - 18/2/2013 - NA - 19/2/2013 - Sick or dead poultry
  • Cambogia - Kampong Cham - 35 - M - 8/2/2013 - 13/2/2013 - 13/2/2013 - 25/2/2013 -  Sick or dead poultry

(...)

 

Public health risk assessment of avian influenza A(H5N1) viruses:

Any time influenza viruses are circulating in poultry, sporadic infections or small clusters of human cases are possible especially in people exposed to infected poultry kept in households or contaminated environments.

However, currently, this A(H5N1) virus does not appear to transmit easily among people and therefore the risk of community level spread of this virus remains low.

Therefore, the public health risk associated with this virus remains unchanged.

 

Human infection with other non-seasonal influenza viruses

No new human case of influenza A(H3N2)v virus infection were reported from the United States of America (USA) or elsewhere.

 

Overall public health risk assessment of the non-seasonal influenza viruses:

Further human cases and small clusters of infections with influenza A(H3N2)v virus may be expected as this virus is circulating in the swine population in the USA.

Continued close monitoring of the situation and the virus is warranted.

Sporadic human cases and small clusters of infections with other influenza viruses might also be expected from the USA and anywhere these viruses are circulating in animal populations to which humans are exposed.

 

Animal outbreaks with high pathogenic avian influenza viruses with potential public health impact

Overall, official reports of animal influenza outbreaks have increased over the past months (http://www.oie.int/wahis_2/public/wahid.php/Diseaseinformation/WI ).

This seasonal pattern is expected with the onset of winter in the northern hemisphere.

Due to the constant evolving nature of influenza viruses, WHO continues to stress the importance of global monitoring of influenza viruses in animals and people and recommends all Member States to strengthen routine influenza surveillance.

All human infections with non-seasonal influenza viruses are reportable to WHO under IHR (2005).

 

Relevant Links:

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1 Sorn, S., et al. Dynamic of H5N1 virus in Cambodia and emergence of a novel endemic sub-clade. Infect. Genet. Evol. (2012), http://dx.doi.org/10.1016/j.meegid.2012.05.013 http://www.sciencedirect.com/science/article/pii/S1567134812002158

 

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