LOS ANGELES, Sept 7: A US porn actor has tested positive for the virus that causes AIDS, the third such case reported in less than three weeks, leading a Los Angeles-based trade group for adult filmmakers to call a fresh nationwide moratorium on Friday on productions. The infections follow a vote last year by Los Angeles County residents to require porn actors to wear condoms when having sex on set, a measure that proponents of the requirement complain is largely going unenforced in the county. (agencies)