From Creatures Wikia
The male norn looks healthy enough, but is NIV positive. Watch him and you will see him infect other norns with the virus. There is rumour that Norn Immuno-deficiency Virus (NIV) does not cause Acquired Immuno-deficiency Syndrome (AIDS). This is false. The virus is spread sexually and does cause AIDS . The norns will not typically die from the NIV itself but from other pathogens in their. NIV norns have an altered genome that is essentally Andrew Carroll's excellent Circulatory Norns genome with a extra genes added to make them susceptible to NIV. The NIV attacks the Killer T cells and other parts of the immune system. The other norns in the pack are a NIV positive female and a monogamous NIV negative couple.
Unfortunately standard norns are obligatorily promiscuous and do not have condoms or anti-retrovirals.