Issue No. 32 - november 2012
Since 2003, H5N1 has killed or forced the culling of more than 400 million domestic poultry and caused an estimated US$20 billion in economic damage across the globe before it was eliminated from most of the 63 countries infected at its peak in 2006. The H5N1 HPAI virus remains endemic in few countries. The number of outbreaks in domestic poultry and wild bird populations shrank steadily from 2003 to mid-2008, rose progressively from mid-2008 to mid-2012 but has decreased since then (See Figure 2b).
During the reporting period, there were 98 domestic poultry outbreaks reported from six (6) countries/territories (Bangladesh, Cambodia, China (including Hong Kong), Egypt, India, Indonesia), nine (9) confirmed reports of human cases in four countries (Cambodia, China, Egypt, and Indonesia ) and five (5) confirmed wild bird events in China (Hong Kong).
The period April to June generally signals the end of the H5N1 HPAI season when reports of outbreaks decrease globally. As expected, during the second quarter of 2012, there were reductions in the number of countries reporting outbreaks (from 11 to 6; see Figure 3a) as well as the number of outbreaks/cases reported globally (198 to 107 Figure 2a).
In addition, the number of outbreaks recorded during this period represents a five-fold decrease in the number observed during the second quarter of 2011 (508 to 103 ;See Figure 1b; 3). This reduction may be due in part to the lower reporting numbers from Egypt and Indonesia, as well as a lack of reports from countries where the disease has occurred sporadically like Japan and the Republic of Korea as well as Vietnam.
Since 2003, 63 countries/territories have experienced outbreaks of H5N1 HPAI. The last newly infected country was Bhutan in February 2010, two years ago. Effective control measures for outbreaks in poultry have been associated with a reduced incidence of human infections in several countries. Even if the apparent decrease in outbreak numbers in poultry (Figure 1b,Figure 2) during the end of the H5N1 HPAI active periods (April to June) for the last three years (2009 to 2012) has resulted in a reduced risk for human infections in affected countries, the fact that the number of countries reporting H5N1 HPAI has remained constant implies a continued infection risk to humans.
The H5N1 virus has infected 608 people since it first appeared in 2003, killing 359 of them, according to WHO figures. The countries reporting human deaths in during the period include Cambodia, China, Indonesia and Egypt.
Although H5N1 HPAI continues to be a global threat for poultry and humans, most countries rely on passive surveillance based on the reporting of clinical cases in poultry. Clinical signs can be masked by the use of regular vaccination in poultry populations. As a result, outbreaks are underreported. Active surveillance in poultry and wild bird species therefore needs to be maintained by governments in endemic countries and countries at risk globally.
Full document, incl. maps:http://www.fao.org/docrep/016/ap387e/ap387e.pdf