a subtype, called "h5n1", killed six people in hong kong in 1997, but did not kill again until 2003, this time in china. until the middle of 2005, it was primarily found in southeast asia but since then has spread to parts of africa and europe. it has killed tens of millions of birds and resulted in the slaughter of hundreds of millions of other birds to limit its spread. so far it is mostly a bird disease and rarely infects humans. the concern about h5n1 is that it is constantly evolving at a very fast rate. it might create a human flu pandemic. governments around the world are spending money to deal with this problem: studying h5n1, creating vaccines, conducting pandemic practice exercises, stockpiling useful flu medication, and many other activities.