HIV is recognized as a health concern in Pakistan with the number of cases growing. Moderately high drug use and lack of acceptance that non-marital sex is common in the society have allowed the HIV epidemic to take hold in Pakistan, mainly among injecting drug users (IDU), male, female and transvestite sex workers (MSW, FSW and TSW) as well as the repatriated migrant workers. HIV infection can lead to AIDS that may become a major health issue. The National AIDS Programme's latest figures show that by the mid-2000s, the number of HIV cases had increased to approximately 0,102 million. This number was estimated little over 4,000, as the HIV cases reported since 1986. The UN and government estimated the number of HIV/AIDS cases around 97,000 ranging from a lowest estimate of 46,000 to a highest estimate of 210,000. More realistic estimates that are based on actual surveillance figures, however, suggest that this number may be closer to 40,000–45,000. The overall prevalence of HIV infection in adults aged 15 to 49 is 0.1%. (0.05% if one accepts the lower estimates). Officials say that the majority of cases go unreported due to social taboos about sex and victims' fears of discrimination. The other reason for all the cases not being reported is that HIV is a disease either not systematically tested for or reported in the routine surveillance system. Evolving phases of HIV epidemic HIV epidemic evolves in three phases. First phase is low prevalence, when prevalence of the disease is less than 5% in any high-risk group of the country. Second phase is concentrated epidemic when proportion of infected people in any high-risk group rises more than 5%. Third and last phase of epidemic is generalized epidemic when prevalence of HIV infection rises over 1% among blood donor or pregnant women. Like other Asian countries, Pakistan is following a comparable HIV epidemic trend having moved from 'low prevalence, high risk' to 'concentrated' epidemic in the early to mid-2000s. Pakistan's epidemic is primarily concentrated among two of the key population groups driving the epidemic in the country. These are people who inject drugs, with a national prevalence of 27.2% (weighted prevalence of 37.8%); followed by transgender sex workers, standing at 5.2% and then 1.6% among male sex workers. The prevalence in female sex workers still remains low at 0.6%. The geographic trend of key populations is from major urban cities and provincial