5/07/2013

Influenza A(H5N1) - Multistate (world) - Monitoring human cases (ECDC/CDTR, May 7 2013, edited)

[Source: European Centre for Disease Prevention and Control (ECDC), full PDF document: (LINK). Edited.]

COMMUNICABLE DISEASE THREATS REPORT

Week 18, 28 April-4 May 2013

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Influenza A(H5N1) - Multistate (world) - Monitoring human cases

Opening date: 15 June 2005 Latest update: 2 May 2013

 

Epidemiological summary

The latest WHO update on 26 April 2013 acknowledged six additional laboratory-confirmed human cases with influenza A(H5N1) virus infection from Bangladesh (one), Cambodia (one), Egypt (two) and Viet Nam (two). The two cases from Egypt both died. The investigations into these cases concluded that they were sporadic cases and that the appearance of sporadic cases is expected and likely to occur in the future.

Since the beginning of 2013, Cambodia has reported ten 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 have a direct epidemiological link 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 and so additional sporadic human cases might be expected.

From 2003 through to 26 April 2013, 628 laboratory-confirmed human cases with avian influenza A(H5N1) virus infection have been officially reported to WHO from 15 countries, of which 374 have died.

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ECDC assessment

Hong Kong reported the world's first recorded major outbreak of bird flu among humans in 1997, when six people died. Most human infections are the result of direct contact with infected birds, and countries with large poultry populations in close contact with humans are considered to be most at risk of bird flu outbreaks. ECDC follows the worldwide A(H5N1) situation through epidemic intelligence activities in order to identify significant changes in the epidemiology of the virus. ECDC re-assesses the potential of a changing risk for A(H5N1) to humans on a regular basis. There are currently no indications that from a human health perspective there is any significant change in the epidemiology associated with any clade or strain of the A(H5N1) virus.

This assessment is based on the absence of sustained human-to-human transmission, and on the observation that there is no apparent change in the size of clusters or reports of chains of infection. However, vigilance for avian influenza in domestic poultry and wild birds in Europe remains important.

 

Actions

WHO is now reporting H5N1 cases on a monthly basis. ECDC will continue monthly reporting in the CDTR to coincide with WHO reporting.

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