Fewer than 400 new HIV cases were reported last year, 9 per cent down from the number in 2008, but doctors warned people to remain on guard.
A total of 396 new cases of HIV infection were reported last year to the Department of Health, down from the record high of 435 in 2008 and 414 in 2007.
Dr Wong Ka-hing, the department's HIV/Aids consultant, said that although the number of new cases was slightly lower than in recent years, Hongkongers should not be complacent.
'We are unable to draw any significant conclusion just because of a decrease in one year,' he said. 'Hongkongers still needed to be alert, such as by having safer sex using condoms.'
In line with recent worldwide trends, transmission through homosexual and bisexual contact was increasing faster than heterosexual cases.
Some 38 per cent of last year's cases were transmitted homosexually, 2.8 per cent via bisexual contact and 26.8 per cent heterosexually.
Most cases involved men aged between 30 and 39. About 70 per cent of homosexual men got the virus in Hong Kong, while the comparable figure for heterosexual men was about 30 per cent.