The incidence of avian influenza infections in humans has increased over the past decade (Table 3) . Initially, cases of avian influenza (H7N7) in humans occurred in association with poultry outbreaks, manifesting as self-limiting conjunctivitis [30, [50] [51] [52] [53] . Then, in 1997, a large scale HPAI H5N1 outbreak occurred among poultry in Hong Kong, with 18 documented human cases [29, 31, 54, 55] . Two subsequent poultry outbreaks in Hong Kong in 1999 and 2003 with HPAI H5N1 occurred without human cases until 2003 when two members of a family in Hong Kong contracted HPAI H5N1 [56] . In December of 2003, HPAI H5N1 surfaced in poultry in Korea and China, and from 2003 to 2006 the outbreak stretched worldwide in the largest outbreak in poultry history. Human cases of HPAI H5N1 followed the poultry outbreak, with a total of 256 cases and 151 fatalities thus far [57] . Other limited outbreaks have occurred, causing variable human disease (Table 3 ) [52, 58] . However, HPAI H5N1 remains the largest and most significant poultry and human avian influenza outbreak.