At any given time, there are approximately ten million people imprisoned worldwide (two million of them in the USA alone). Prison populations come largely from the most marginalised groups in society, people in poor health and with chronic untreated conditions, the vulnerable and those who have engaged in activities with high risk of HIV exposure, such as injecting drugs and sex work. At some point, the vast majority are released into the wider community.

The situation is exacerbated by high rates of tuberculosis (often multi-drug resistant), sexually transmitted infections and hepatitis B and C. According to the World Health Organization’s European Office in 2002 TB prevalence in prisons in the Russian Federation was 9.8%, syphilis incidence 1.2%, and 20-40% of all prisoners were living with hepatitis C.

Evidence of high HIV prevalence in prison is widely available. Globally, most prisoners are men, but women prisoners are also at risk of HIV. In Brazil, Canada, UK and the United States, women prisoners are more likely to be HIV-positive, largely because a high proportion is incarcerated for drug use and sex work.

A large proportion of prisoners are drug users. In Europe this can range from 30% (Italy) to 70% (Portugal). According to the UN Office on Drugs and Crime, (UNODC), in the Russian Federation in some prisons up to half of all inmates are injecting drug users, while in Kazakhstan the proportion is close to two-thirds.

In many countries detention centres are breeding grounds for HIV infection. Overcrowding, homosexual relations, gang violence, lack of protection for the weakest inmates, and corrupt prison management create an environment that increases vulnerability to HIV transmission through unsafe sexual practices, sharing of injecting equipment or crude substitutes, tattooing, violence and rape.

According to data from the Canadian HIV/AIDS legal Network, prisons are overcrowded in over 100 countries, with prisons housing four to five times the numbers of inmates originally planned. As a consequence, around the world the percentage of people with HIV/AIDS in prisons is significantly higher than in the community.

When it comes to data on the prevalence of HIV among prisoners and prevention and treatment programmes within prisons, information is highly variable. Within Europe, surveillance of HIV-positive prisoners and approaches to harm reduction varies widely, and in the USA approaches differ from state to state.

For the rest of the world, in particular the developing world, any data is at a premium. The Canadian HIV/AIDS Legal Network, at the 2004 Bangkok conference, reported that a survey of international information on HIV in prisons and HIV among indigenous intravenous drug user (IDU) populations produced only 29 countries with any information.

The Conference Summary commented: “The risk of HIV in prison has similarly not been the subject of intensive investigation by prevention researchers in developing countries. The triple stigmatisation of incarceration, drug injecting and HIV or hepatitis C infection have all but guaranteed a low priority to programming in this area.”

Internationally the terminology in surveying prisons is problematic; prisons, juvenile prisons, prisons for mentally ill offenders, pre-trial and remand centres, police detention centres – all may be included or discounted by national authorities. Prison populations are dynamic with occupation rates varying in terms of overall incarceration rates and length of imprisonment.

However, the accumulation of data must be a priority, according to UNAIDS.

Forcing the issue is the growing realisation that prisons are not just repositories of blood-borne viruses but have been the springboard for fuelling the epidemic of HIV/AIDS TB and Hepatitis. “Prisons are HIV factories,' said Elizabeth Pisani of Family Health International, an AIDS prevention group in Jakarta. ``We are introducing a population that we know to be infected with the virus into an environment where people shoot up drugs and have anal sex.' (Associated Press, 1 December 2004)