Australia's HIV infection rate has increased 10 per cent in just one year, according to the latest Australia Annual Surveillance Report by Kirby Institute. The rate of newly diagnosed HIV infections in the country is now the largest increase in 20 years.

In 2012, 1,253 Australians were diagnosed with HIV with unprotected sex among men as the most common method of transmission. The report also revealed that the number of new HIV patients has been gradually rising in the last 14 years from only 719 HIV cases in 1999.

The latest HIV figures in Australia will be formally released at the Australasian HIV/AIDS Conference 2013 in Darwin.

The highest number of HIV cases has occurred among gay men who have unprotected sex with other men at 67 per cent, while 25 per cent came from unsafe heterosexual contact. Only 2 per cent came from using contaminated needles for drug use.

Among the newly diagnosed HIV infections from heterosexual contact, 58 per cent of them are people from Southeast Asia and from the Sub-Saharan Africa or those who have sexual partners from these parts of the world.

Since the HIV virus was made known, the report has estimated that between 28,600 to 34,300 Australians have HIV.

According to Professor John de Wit of the National Centre in HIV research, the main contributor to the rise in HIV infections was the possibility of exposure to the virus through "unprotected anal sex."

Professor de Wit is one of the authors of the Annual Report of Trends in Behaviour 2013. The annual report on HIV changing trends will also be released at the Darwin conference on Oct. 21.

In the Annual Report of Trends, the number of gay men engaging in unprotected and casual sex has increased with 40 per cent of gay men admitting to unsafe sex in 2012. Professor de Wit said this trend is more rampant among men diagnosed with HIV and those who were below 25 years of age. Mr de Wit said most gay men may be less than likely to be aware of HIV prevention.

Starting HIV treatment early on may be a major factor in reducing the risk of HIV transmission, according to infectious disease expert Edwina Wright, who is also an Associate Professor at Monash University and Burnett Institute.

Professor Wright said that if a HIV-diagnosed patient will undergo three to six months of treatment, HIV transmission is reduced to 96 per cent. She said there is sufficient evidence to support the idea of early treatment as a cost-effective method with more health benefits to the patient.