Germany, Poland and Belgium are among the latest European countries to report outbreaks of avian influenza – more commonly known as bird flu. The highly contagious viral disease has led to the culling of hundreds of millions of birds globally. The H5N1 virus, the most prevalent strain of bird flu, was first reported in China in 1996. But the strain currently circulating globally is an extremely dangerous subtype of H5N1, which emerged in Europe in 2020.