PNGs HIV epidemic is predominately driven through heterosexual transmission. That said, other modes of transmission observed include vertical transmission and male-to-male sex. A few sporadic cases of HIV have been diagnosed whereby the mode of transmission has been reported as tattooing and injecting drug use. The data on those who have been diagnosed with HIV as a result of injecting drug use is sparse. It is unclear for example if such people are indeed ethnic Papua New Guineans or if in the case of expatriates the virus was contracted via injecting drug use practices outside of PNG. There have been other anecdotal, but unverified, reports of injecting drug use occurring in PNG and concern has been raised over this being a possible route of transmission that with the potential of contributing to the epidemic.