Of the approximately 35 million people living with HIV across the globe, over 1.6 million are Tanzanian.

The human immunodeficiency virus (HIV), a mutation of the simian immunodeficiency virus (SIV), originated in the Democratic Republic of the Congo (DRC) in the late 1950s, though ancestors of the pathogen are suspected to have been present for decades before throughout Central Africa. The rapid transition of colonized populations from rural to urban areas in postwar years led to the emergence of more effective modes of transmission of the virus, such as mass vaccinations and prostitution. Eventually, in 1959, the first certain case of the illness appeared, ushering in one of the most severe threats to human health in history.

The country was one of the worst affected by the crisis when it emerged on a global scale in the 1980s. The first three cases were reported in 1983, and since then the virus has spread to an unprecedented degree, going on to affect the whole nation and leading to the challenging situation now faced by its citizens; a generalized epidemic. Over 6% of the population is HIV positive, that is, 1.6 million people, with hundreds of new cases reported every day. The prevalence of prostitution in some urban locations and around mines and other industrial or agricultural areas, in addition to a rising number of intravenous drug users that is the direct result of Tanzania's ports becoming transit points for Asian narcotics en route to Europe, has allowed the infection to spread extensively across all strata of society, and among young men in particular. Transient workers who move to industrial or mining areas often come into contact with sex workers, allowing the infection to spread as they move around for jobs. In addition, fishermen and port workers, who come in contact with populations from other affected nations, continue the spread of AIDS. Women are vastly more susceptible to contracting the disease, a full 40% more likely than males, a function of gender imbalances within the country. Many younger women marry older males, putting them and their children at risk and perpetuating the disease among new generations. Furthermore, the interaction of populations living in border regions or along the Great Lakes results in higher rates of infection, with one in five people in these regions being HIV positive. In contrast, the citizens of Zanzibar, Tanzania's island province in the Indian Ocean, have an infection rate of just 0.6%.

In response to the crisis, and particularly to the disparity of risk faced by females, the government has initiated numerous campaigns and strategies intended to deal with divergent aspects of the threat. At the highest level, the state is working to combat the spread of AIDS, setting up the Tanzania Commission for AIDS (TANZAID), which is part of the Prime Minister's Office, between 2000 and 2001. This body is legally obligated to spearhead the fight against the disease, coordinating all organizations involved in its eradication. With a vision that aims to provide care and support for those afflicted by the sickness, a key element of the national strategy is to focus on prevention, encouraging low risk behavioral changes and a dynamic plan to reduce HIV passed on during birth. Over 200,000 children in Tanzania live with HIV, while approximately 1.3 million have lost their parents to the epidemic. One-fifth of new HIV infections are passed down from mothers to babies, a problem that is being dealt with through the use of antiretroviral medicines and safer feeding practices for children.

On a broader scale, preventative measures have been adopted by authorities for other social groups in the country. The WHO states that approximately 40% of those in need of treatment are receiving it, but this remains a challenge considering the overall deficiencies of the health system. With only 0.02 doctors for every 1,000 citizens, the country faces an uphill struggle to continue dealing effectively with the burden. Despite the establishment of TANZAID as a coordinating body for policy, the fact that much of the funding directed at controlling the disease comes from external donors means that the government's strategy is frequently undermined, and their focus on preventative measures is not necessarily receiving the support it should. Overall, figures for infection are falling, though sustained funding from the state, along with that of foreign donors, and a more comprehensive integration of this support is needed to guarantee long-term success.