Accurate estimates of the number of people diagnosed and living with HIV infection within a health jurisdiction provide the basis for planning of clinical service provision. Case reporting of new diagnoses does not account for inwards and outwards migration of people with HIV infection, thereby providing an inaccurate basis for planning.

The Victorian passive surveillance system records all cases of HIV diagnosed in Victoria and distinguishes between new Victorian diagnoses (cases whose first ever HIV diagnosis was in Victoria) and cases previously diagnosed interstate and overseas. In order to gain an understanding of the impact of population movement on the burden of HIV infection in Victoria, we compared the characteristics of people first diagnosed in Victoria with those previously diagnosed elsewhere.

Between 1994 and 2007 there were 3111 HIV notifications in Victoria, including 212 (7%) 'interstate diagnoses' and 124 (4%) 'overseas diagnoses'. The proportion of cases diagnosed outside Victoria increased from 6.4% between 1994 and 2000 to 13.8% between 2001 and 2007. Compared with 'new diagnoses', a larger proportion of 'interstate diagnoses' reported male-to-male sex as their HIV exposure, were Australian-born and diagnosed in Victoria at a general practice specialising in gay men's health. Compared with 'new diagnoses', a larger proportion of 'overseas diagnoses' were female, reported heterosexual contact as their HIV exposure, and were diagnosed in Victoria at a sexual health clinic.

Between 1994 and 2007 more than 10% of Victorian HIV diagnoses were among people previously diagnosed elsewhere. Characteristics of both interstate and overseas diagnoses differed from new diagnoses. Service planning needs to be responsive to the characteristics of people moving to Victoria with previously diagnosed HIV infection.