World Health Organisation
The WHO is the directing and coordinating authority for health within the United Nations system. It is responsible for providing leadership on global health matters, shaping the health research agenda, setting norms and standards, articulating evidence-based policy options, providing technical support to countries and monitoring and assessing health trends.
For the purposes of this site the list of key diseases is of especial importance as it provides useful clear information about major diseases, causes, where they are found and precautions, the link here is
According to the site, the infectious diseases described in this chapter have been selected on the basis of the following criteria:
diseases that have a sufficiently high global or regional prevalence to constitute a significant risk for travellers;
diseases that are severe and life-threatening, even though the risk of exposure may be low for most travellers;
diseases for which the perceived risk may be much greater than the real risk, and which may therefore cause anxiety to travellers;
diseases that involve a public health risk due to transmission of infection to others by the infected traveller.
Information about available vaccines and indications for their use by travellers is also provided in a separate Chapter.