Incarcerating drug offenders and users in Australian prisons helps the spread of hepatitis C and hepatitis B, Professor Kate Dolan from the UNSW says.

A leading expert on drug dependency warns that the imprisonment of drug users could lead to an explosion of hepatitis in Australia.

Reducing imprisonment rates among people who inject drugs will be crucial to preventing the spread of hepatitis over the next 15 years, says Professor Kate Dolan from the National Drug and Alcohol Research Centre at UNSW.

She says while Australia has successfully contained HIV in prisons compared with other regions across the world, the rate of hepatitis C and hepatitis B in the country's prisons is worryingly high.

Hepatitis C infection levels in Australian prisons range from 22 per cent to 31 per cent, which are much higher than in Western Europe where it ranges from 12 per cent to 19 per cent, says Prof Dolan.

Transmission rates of Hep C in Australian prisons are also much higher than in Scotland, the US and Spain.

Rates of hepatitis B in Australian prisons are also higher, ranging from 11 per cent to 28 per cent, compared with 5 to 30 per cent in western Europe.

Prof Dolan, who will speak at the 21st international AIDS Conference in Durban, South Africa, next week, argues against the mass incarcerations of drug users, which is an "expensive, ineffective and inhumane approach" to drug dependency.

It had become a serious public health issue as an estimated 100,000 people went through the prison system each year.

Prisons could act as an incubator of HIV and hepatitis and with the high level of mobility of prisoners infection transmission in prison was a major public health concern.

A wealth of evidence from around the world suggested Australia needed to consider alternatives to prison sentences, said Professor Dolan.

Mathematical modelling, published in the medical journal The Lancet, suggested reducing the imprisonment of people who injected drugs would significantly control infections in prisons and the wider community.

The authors of the Lancet study also warn that women and girls are among the fastest-growing group imprisoned for drug offences.