It sounds like a bizarre story, but it was published in this month's issue of AIDS Research and Human Retroviruses. In their paper, the authors say the 22-year-old Brazilian woman had shared nail tools (including cuticle scissors) with a manicurist cousin about 10 years earlier. That cousin was later diagnosed as HIV-positive. But, at the time, the family didn't know about the cousin's status. Now, lab tests for this 22-year-old with no reported symptoms and no history of any other traditionally risky behaviors (e.g., having unprotected sex) have showed signs of a longstanding HIV infection.
So, with no other infection possibilities, the authors conclude that the patient contracted HIV from those nail tools 10 years ago, in a similar manner as one might contract the infection from a shared needle. But, the researchers say this is a very rare event; if you bring your own tools or your salon has a no-sharing policy, you aren't in danger. So, get your mani on — with proper hygiene, of course.