Risks factors for HIV infection are common to other diseases. There are numerous HIV co-infections, but several of these, including tuberculosis, hepatitis B and hepatitis C, contribute importantly to morbidity and mortality globally. In addition, certain sexually transmitted infections (STIs) are common in HIV-infected individuals. Of these STIs, there is a global focus on the joint elimination of HIV and syphilis. The website provides resources on diagnostics for each of these co-infections.