As for your aunt, for starters, despite the fact that she
uses injection drugs, statistically the chances are that she is not infected with HIV. Even if, as a worst case scenario, she does have HIV, acquisition of HIV through oral exposures, including oral sex is virtually non-existent and there are NO instances in which HIV has been transmitted on an inanimate object such as a toothbrush. The virus is just not very tough and does not live long in the environment.