This post is just to note which States are considered to be a party to them and what they mean in general terms.
A blog-friendly reformatted excerpt from the Foreward (highlighting is mine)...
"The purpose and scope of the IHR (2005) are “to prevent, protect against, control and provide a public health response to the international spread of disease in ways that are commensurate with and restricted to public health risks, and which avoid unnecessary interference with international traffic and trade.” The IHR (2005) contain a range of innovations, including:
- (a) a scope not limited to any specific disease or manner of transmission, but covering “illness or medical condition, irrespective of origin or source, that presents or could present significant harm to humans”;
- (b) State Party obligations to develop certain minimum core public health capacities;
- (c) obligations on States Parties to notify WHO of events that may constitute a public health emergency of international concern according to defined criteria;
- (d) provisions authorizing WHO to take into consideration unofficial reports of public health events and to obtain verification from States Parties concerning such events;
- (e) procedures for the determination by the Director-General of a “public health emergency of international concern” and issuance of corresponding temporary recommendations, after taking into account the views of an Emergency Committee;
- (f) protection of the human rights of persons and travellers; and
- (g) the establishment of National IHR Focal Points and WHO IHR Contact Points for urgent communications between States Parties and WHO."
This was taken from the PDF of the IHR2005 
- International Health Regulations 2005