Cluttering e-mail inboxes again last fall was an urban hoax stirred up back in 2000: HIV-infected needles attached to the underside of gas pumps prick unsuspecting customers. Besides the fact that the reports had been debunked on, the Internet’s leading urban-legend investigator, the CDC took the rare step of issuing a statement reminding the public that discarded needles pose an extremely low risk of HIV -- even in hospital settings.