Before 1983, medical professionals in Tanzania took Acquired Immunodeficiency Syndrome (AIDS) as a disease occurring in America and Europe . Very little attention was focused on this disease. In October 1983, some doctors working in Bukoba hospital, Kagera Region, started to see patients presenting with prolonged diarrhoea accompanied by severe loss of body weight, thinning of body muscles, chronic fever, oropharyngeal candiadosis and genital ulcers. The first 3 patients with AIDS were reported from Ndolange Hospital in the Kagera region in November 1983. The clinical features of these patients were clearly similar to those reported in Rwanda and Zaire. Soon after this alarm, more and more cases were reported from this region and by late 1985 these cases were serologically confirmed by the enzyme- linked immunosorbent assay (ELISA) and Western blot tests.

Initial observation of AIDS cases as reported in Kagera pointed out that the early cases were among adults of both sexes who were involved in cross-border trade, the war, commercial sex workers and truck drivers. This population group indeed, accelerated HIV transmission to other parts of the country; starting with urban centres and then on to the rural areas. The disease was nicknamed "Juliana" after the label on clothes fashionable at that time among prosperous businessmen and women, imported from a neighboring country.

Although between 1983 and 1987 Kagera region continued to report increased numbers of AIDS patients more than any other region, by 1986 all regions of Tanzania Mainland had reported AIDS cases to the Ministry of Health

There may be underreporting of cases because of inadequate clinical and laboratory diagnostic services throughout the country. It is also likely that multiple reporting of cases may be occurring, weak AIDS case surveillance system and the possibility of patients attending for treatment in different hospitals in the country. Most cases of AIDS have been reported from the age groups of 0-5 years and 15- 45 years with both sexes equally represented. In general, AIDS and HIV infection is more prevalent in urban areas. In a large community based sero survey in Kagera region, the HIV infection prevalence rates ranged from less than 0.5% per cent of the total population in Karagwe, Ngara and Biharamulo to over 30% per cent of adults in Bukoba town.

Between 5% percent and 10% percent cent of blood donated for transfusion and screened for HIV in Iringa, Mbeya and Dar es Salaam in 1988 had HIV antibody. Moreover, between 5% per cent and 23.7% per cent of antenatal clinic attendees screened for HIV at Mwanza, Bukoba and Dar es Salaam had HIV antibody. The epidemic of AIDS and HIV infection in Tanzania is associated solely with HIV-1, although elsewhere in the world infections due to HIV-2 also occur. According to analysis of the genetic diversity of HIV-1 in samples from Dar es Salaam and Kagera (Lyamuya et al, 1998) and from Mbeya (Hoelscher et al, 1998) three viral subtypes are common in Tanzania : HIV-1 subtype A, C and D.

It can be argued that the mobility of people and social disruption caused by the war between Uganda and Tanzania that ended in 1979 were a conducive environment for the introduction of the human Immune-deficiency Virus (HIV) and a fertile ground for its spread. Furthermore, after the war, serious economic recession gripped the country.

As the epidemic continued to unfold in an exponential manner, it became clear that the epidemic required urgent control measures, including studies aimed at assessing the extent of HIV-1 infection in the population. The first sero-survey (an epidemiological study involving serological testing using enzyme-linked immunosorbent assay (ELISA) was conducted among groups of patients and healthy individuals in Arusha, Dar es Salaam, Kagera, Mwanza regions on mainland Tanzania between 1985 and 1987. The study showed that HIV-1 prevalence rates among pregnant women in these regions were quite substantial, ranging from 0.7% in Arusha region to 16.0% in the Kagera region. Furthermore, the results of this study demonstrated that even as early as 1987, the HIV epidemic had already found its way among population groups considered to be a low risk of HIV infection.

The high HIV infection rates implicitly suggested the need for urgent control measures that should be coordinated through a National AIDS Control Programme (NACP) which was established in 1988 to co-ordinate all HIV/AIDS activities in the country. Also it acted as a link between the government actors and non-government actors (NGOs) in the fight against HIV and AIDS.

Since the establishment of the National AIDS Control Programme (NACP), the progression of the epidemic has been monitored through unlinked, anonymous testing of blood from pregnant women attending ante-natal clinics for the first time in selected sentinel sites.

Current epidemiological data:

A total of 13,285 AIDS cases were reported to the NACP from 21 regions during the year 2005. This resulted into a cumulative total of 205,773 reported cases since 1983 when the first AIDS cases were in Tanzania. In 2003, Tanzania Mainland was estimated to have about 1,840,000 people living with HIV (860,000 males and 980,000 females ) (HIV/AIDS/STI Surveilance Report no. 19). A total of 16,430 AIDS cases were reported to the NACP from 21 regions during the year 2004. This resulted into a cumulative total of 192,532 reported cases since 1983 when the first AIDS cases were in Tanzania. In 2005, Tanzania Mainland was estimated to have about 1,1,770,383 people were living with HIV. of these 656,180 are from urban and 1,114,203 are from rural areas (HIV/AIDS/STI Surveilance Report no. 19).

Modes of Transmission:

In Tanzania , HIV is mainly transmitted through heterosexual intercourse or from mother to child.