For Australian travellers it is essential that you check out the Department of Foreign Affairs and Trade website or the Smart Traveller site and look up the government's travel warnings, individual country information and even register your trip online (which helps DFAT assist you in cases of emergency).

Also useful is the travel advice sites operated by these governments:

Canada

United Kingdom

New Zealand

United States

For a general overview of health issues around the world then check out the World Health Organisation website