The World Health Organization (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.
www.who.int

AIDS Organisations Worldwide provides contact details and service profiles of HIV/AIDS and relevant organisations throughout the world.
www.aidsmap.com

The Joint United Nations Program on HIV/AIDS (UNAIDS) is a leading advocate for global action on HIV/AIDS. It leads, strengthens and supports an expanded response aimed at preventing transmission of HIV, providing care and support, reducing the vulnerability of individuals and communities to HIV/AIDS, and alleviating the impact of the epidemic. The site contains information about specific countries and links to many HIV/AIDS related sites.
www.unaids.org

The Centers for Disease Control and Prevention is a federal agency of the United States. It provides health information, monitors the spread of dangerous and life-threatening diseases and responds to public health emergencies and natural disasters.
www.cdc.gov

The World Hepatitis Alliance provides global leadership to help eliminate viral hepatitis as a public health threat by 2030. It works with governments, members and partners to elevate the voices of people living with viral hepatitis, to raise the profile of viral hepatitis and to help establish comprehensive hepatitis prevention and treatment strategies.
http://www.worldhepatitisalliance.org/