The United Kingdom's Health Protection Agency reported Monday that the number of people in the country living with HIV climbed by 20% in 2002, with nearly 50,000 Britons now infected with the virus. HPA officials say as many as one-third of those who are HIV-positive are unaware that they are infected. Newly diagnosed HIV cases in 2002 were estimated at about 6,400, about 32% of which occurred in the U.K., and the rest coming primarily from immigrants infected in their countries of origin. Of the infections occurring in the United Kingdom, four-fifths were reported among gay and bisexual men. Other sexually transmitted diseases also are on the rise in the U.K., particularly among men who have sex with men, the HPA reported. Gonorrhea cases among gay men doubled in 2002, while new syphilis cases among gay men rose from 52 in 2001 to 607 in 2002. HPA is calling for sexual health clinics to offer gay and bisexual men annual HIV tests and screenings for other STDs to help stem the spread of the diseases.