This article analyses how the 'securitization' of highly pathogenic avian influenza (H5N1) contributed to the rise of a protracted international virus-sharing dispute between developing and developed countries. As fear about the threat of a possible human H5N1 pandemic spread across the world, many governments scrambled to stockpile anti-viral medications and vaccines, albeit in a context where there was insufficient global supply to meet such a rapid surge in demand. Realizing that they were the likely 'losers' in this international race, some developing countries began to openly question the benefits of maintaining existing forms of international health cooperation, especially the common practice of sharing national virus samples with the rest of the international community. Given that such virus samples were also crucial to the high-level pandemic preparedness efforts of the West, the Indonesian government in particular felt emboldened to use international access to its H5N1 virus samples as a diplomatic 'bargaining chip' for negotiating better access to vaccines and other benefits for developing countries. The securitized global response to H5N1 thus ended up unexpectedly entangling the long-standing international virus-sharing mechanism within a wider set of political disputes, as well as prompting governments to subject existing virus-sharing arrangements to much narrower calculations of national interest. In the years ahead, those risks to international health cooperation must be balanced with the policy attractions of the global health security agenda.