The SARS epidemic that broke out in late 2002 in China's Guangdong Province highlighted the difficulties of reliance on state-provided information when states have incentives to conceal discrediting information about public health threats. Using SARS and the International Health Regulations (IHR) as a starting point, this article examines negotiated information orders in global public health governance and the irregularities in the supply of data that underlie them. Negotiated information orders within and among the organizations in a field (here, e.g., the World Health Organization, member states, government agencies, and international non-governmental organizations) spell out relationships among different categories of knowledge and non-knowledge - what is known, acknowledged to be known, and available for use in decision making versus what might be known but cannot be acknowledged or officially used. Through information leveraging, technically sufficient information then becomes socially sufficient information. Thus it is especially information initially categorized as non-knowledge - including suppressed data, rumour, unverified evidence, and unofficial information - that creates pressure for the renegotiation of information orders. The argument and evidence of the article also address broader issues about how international law and global norms are realigned, how global norms change, and how social groups manage risk.