At least 19,435 Iranians have been infected with the HIV virus, with more than 1,000 new cases recorded since December 2008, the ISNA news agency reported on Sunday, quoting the health ministry.
Of those infected, 1,875 are already confirmed as having AIDS, it said.
It said the highest rate of HIV infection, 40.2 per cent, was among the 25 to 34 age group, with most victims being men. Males accounted for 93.3 per cent of all infected cases.
With testing facilities limited and HIV-infected people or those living with AIDS often unwilling to come forward, the health ministry estimates that Iran actually has 80,000 HIV cases -- four times higher than the registered figure.
According to official ministry figures, however, at least 3,236 people have died in Iran after developing full-blown AIDS, although the report did not say when such deaths started being recorded.
The main cause of infection remained intravenous drug use, the report said, with 77.5 per cent of people contracting the virus this way.
Infection through sexual contact accounted for 13.1 per cent, while transmission from mother to baby accounted for 0.