Influenza pandemics are recurring events that can potentially lead to millions of human fatalities (Fauci, 2006). Since 1996, lineages of influenza A subtype H5N1 have spread from their origin in China to other regions in Asia, Russia, India, Pakistan, the Middle East, Africa, and Europe (Chen et al., 2006; WHO, 2008). Between 2003 and September 2008, there have been 387 documented cases of human infection by H5N1, with a mortality rate of 63.3% (WHO, 2008). To date, most cases of human infection have been the result of direct transmission from birds (Writing Committee of WHO, 2005). In contrast, some groups have reported evidence of limited human-human transmission (Ungchusak et al., 2005;Hien et al., 2008). The spread of H5N1 to humans and the high mortality rate of those infected have led to concerns that, should H5N1 become widely transmissible among human, it may start the next influenza pandemic (Guan et al., 2004;Cinti, 2005;Longini et al., 2005;Webster et al., 2006). In preparation for such an event, businesses, governments, and health organizations have made stockpiling of antiviral drugs an important component of pandemic preparedness. At the same time, resistance to a class of antiviral drug, adamantanes, has evolved in other influenza A populations as well as in several lineages of H5N1 (