Highly pathogenic avian influenza H5N1 was detected in China in the 1990s, but strongly re-emerged in 2003. It continues to spread.
While the virus strain was first identified in Scotland in 1959, the “Asian lineage” HPAI H5N1 strain now present in Asia is very different to what was first identified more than 55 years ago, and its ability to mutate makes its true threat difficult to measure.
The U.S. may have experienced difficulties with avian influenza over recent months and has been the focus of attention. For much of Asia, the virus has been a constant concern for a decade, resulting in the death and destruction of millions of farmed birds and a significant number of human deaths.
Several countries are considered to be endemic for the HPAI H5N1, and while some may have reported only limited outbreaks, migratory birds and poorly regulated trade mean that, to a varying degree, the threat is ever present.
For some countries, the disease has significantly changed how poultry is sold, due the risk to human health, and resulted in a reconsideration of broader biosecurity measures. However, a failure to apply good biosecurity measures, or to carry out thorough monitoring in more difficult-to-reach areas, are thought to be behind the virus’s continuing circulation in some of the countries listed above.