To the end of June 2005, 4,284 injecting drug users have been reported to be HIV–positive in the UK, 69% of them men.

There is relatively little ongoing transmission of HIV among injecting drug users (IDUs) in the UK. In 2004 the proportion of HIV infections attributable to intravenous drug use was less than 2% of the total, and the HPA estimated that in 2003 there were an estimated 1800 injecting drug users living with HIV infection in 2002, of whom around 22% were unaware of their infection.

The fact that only about 3.5% of the HIV-positive population got HIV through injecting drug use in probably the UK’s biggest prevention success. Not only the proportion, but the absolute number, of HIV infections in IDUs consistently declined between the late 1980s and 2000, at the time infections in other groups have increased, and now appears to be holding steady (see chart below).

(Source: HPA)

In comparison 22% of people with HIV in France acquired it through injecting drugs, 30% in the USA, 34% in Ireland and 49% in Portugal, while in the countries of Eastern Europe injecting drug use is (as yet) the predominant mode of acquisition (76% of cases in Russia).

The majority (40%) of all HIV diagnoses among injecting drug users have been in London, and the overwhelming majority of the remainder have been diagnosed in Scotland (29%). Injecting drug users have declined as a proportion of newly diagnosed HIV–positive individuals in Scotland from 77% prior to 1986 to 4% in 2004.

Injecting drug users make up 30% of all diagnosed HIV–positive individuals in Scotland, compared with 3.5% across the rest of the UK.

Twenty-nine per cent of IDUs have been reported as having AIDS. This is the same proportion of AIDS cases and among all people with HIV. But 36% are known to have died as opposed to just 23% of all people with HIV. A large proportion (42%) died without AIDS being reported. This is to be expected, since liver disease due to hepatitis B and hepatitis C and drug overdoses are common among injecting drug users.

Data are available on country of infection for around 30 per cent of all HIV diagnosed injecting drug users; 817 reported a probable country of infection. Thirty two per cent (262/817) gave the UK as their probable country of infection. This was followed by Italy (20%, 162), Spain (13%, 108), Portugal and the Azores (8%, 66) and Ireland (4%, 34). This would indicate that infections acquired abroad, particularly in Southern Europe, are making a significant contribution to HIV infections reported in the UK.

It is difficult to be sure how widely HIV has spread amongst injecting drug users owing to the difficulty in estimating how many people have injected drugs and shared injecting equipment at some time in the past. The issue is further complicated by the fact that UK estimates have tended to be based on surveys of the current UK population, and do not take into account the extent of migration amongst injecting drug users. The likelihood of having injected drugs in the past is greater for migrants from southern European countries.

Nevertheless a number of strong clues exist regarding prevalence. 2.5% of both male and female IV drug users who seek an HIV test have been HIV–positive (see Public Health Laboratory Service Quarterly Tables). Unlinked anonymised seroprevalence studies suggested a prevalence of 4.7% in drug users attending syringe exchanges or drugs agencies in London in 1995 (less than 2% in men under 25, but up to 8% amongst those between 30–34, suggesting that those who were more likely to have been injecting in the mid–1980s were most likely to be infected. The same wasn't true for women; under 24s were the most likely to be infected).

By 1997 the HIV prevalence among male injecting drug users in London had fallen very slightly, to 4% in men and 1.5% in women. Prevalence declined more significantly outside London, to 0.3%. In 1999 prevalence of HIV infection among those who had begun injecting in the UK in the previous 3 years was estimated at 0.1%. This had fallen from 0.3% in the mid 1990s.

HIV has spread much less widely amongst injecting drug users in the UK than in southern European countries. For the large part this is due to the widespread introduction of needle/syringe exchange schemes before HIV had become widely disseminated amongst the drug using population in the UK. The number of cases of HIV infection and AIDS amongst injecting drug users may also be lower than other European countries because less injecting drug use has taken place in the UK and because less needle sharing took place. A Public Health Laboratory study in 1995 estimated that between 50,000 and 77,000 people in England and Wales were currently injecting drugs, with a subset of between 10,000 and 15,000 who risked blood-borne infection by sharing injecting equipment (Heptonstall).

Although prevalence surveys amongst drug users in several British cities have shown stable or even declining prevalence in the past few years, new infections may still be occurring at a significant rate. Apparently declining or stable prevalence could be explained by:

• Seropositive drug users entering methadone treatment and hence no longer being recruited to prevalence studies through syringe exchanges.
• Migration of HIV-positive drug users to other cities, and their replacement in prevalence studies by HIV-negative users.
• Lack of contact between drug users who continue to share and drugs services which are offering treatment, from which prevalence studies have been recruited.

Apparently stable prevalence may also be explained by increasing levels of HIV testing amongst injecting drug users, which leads them to access drugs services and hence be more likely to be recruited to prevalence studies. This would cancel out the effect of injectors moving to other locations or dropping out of the drug using population.

However, the 1997 Anonymised Seroprevalence report noted that of 292 injecting drug users who had reported starting to inject in the past three years, only one had HIV infection. In comparison, almost 10% were already infected with hepatitis B.

The Unlinked Anonymous Prevalence Monitoring Programme survey of injecting drug users provides prevalence data for hepatitis B and C as well as HIV. Prevalence data are available for those injecting drug users who began injecting in the three years before the date of the survey which they were included in. Many of those who have been injecting for less than three years (so called new injectors) will have been aged under 25 at the time of the survey, however, many young injectors will have been injecting for more than three years and other individuals started injecting later in life.

HIV–positivity amongst injecting drug users is highest in London, Edinburgh and Dundee. Outside these cities very low levels of infection have been found.

In Edinburgh, prevalence amongst current injecting drug users was around 20% in a 1992 survey, although a 1989 study amongst current injectors attending a general practitioner in the worst affected district of Edinburgh showed seroprevalence of 64%. The rate of new infections is thought to be very low due to a decline in syringe and needle sharing and the decline in injecting amongst HIV–positive drug users, many of whom are now receiving methadone treatment or have ceased drug use altogether.

In 1995 the Communicable Disease Surveillance Centre reported that nearly one in five people injecting drugs and attending specialist agencies in London and the South–East reported recent sharing of injecting equipment, and that sharing was more common amongst younger drugs users and amongst women. A similar rate was found in 1997, and when the definition of sharing was expanded to include the sharing of spoons, filters and water, the proportion increased to 57%. These findings have particular relevance for hepatitis C prevention, which is much more easily transmitted by these practices than HIV.

Injecting drug use has been raised as a particular problem in prisons, but preliminary UK studies suggest that there has been little spread of HIV through needle-sharing in prison in comparison with other European countries. Nevertheless, research in the UK indicates that around a third of drug users inject whilst in prison, that a majority of injectors report sharing needles in prison and that between half and three quarters of injectors report have been in custody whilst dependent on drugs or shortly after ceasing drug use.

Twenty-five per cent of injecting drug users in a 1992 anonymised study of a Scottish jail were HIV–positive, although only 4.5% of all prisoners in the jail were infected. A screening exercise at Glenochil prison identified at least 13 inmates who are believed to have been infected from the same source through sharing needles whilst imprisoned, and it is estimated that between 22 and 43 inmates had been infected altogether.

Two recent surveys suggested that in London undocumented HIV infection among drug users could be on the increase. A survey of 27,932 drug users given unlinked anonymous HIV saliva tests found that HIV prevalence specifically in London was 5%, four times the national average and 13 times the prevalence outside London.

Annual incidence among new drug users was estimated to be 2.5% – comparable with that in gay men – though this fell to 0.8% after the first year as people became more informed about HIV risks and better at cleaning ‘works’. Drug users recruited in community settings (streets, needle exchanges etc) had six times the HIV prevalence of drug users using established agencies, suggesting a population of newer users underserved by standard programmes.

Another survey of 428 drug users mainly in London found an HIV prevalence of 4%, a hepatitis C prevalence of 44%, and found that 24% of individuals at baseline saying that they had shared needles and syringes and 54% reporting the sharing of drug use paraphernalia.

References

Donoghoe M et al: HIV testing and unreported positivity among injecting drug users with no treatment experience, AIDS 7: 1105-1111, 1993.

Heptonstall J et al: How many people in England and Wales risk infection from injecting drug use? Communicable Disease Report 5: 40-44, 1995

HIV and AIDS in injecting drug users in the United Kingdom. Communicable Disease Report 9: 35, 1999.

HIV and AIDS in injecting drug users in the United Kingdom. CDR Weekly 10: 34, 2000.

Hope V et al. HIV prevalence among injecting drug users in England and Wales 1990 to 2003: evidence for increased transmission in recent years. AIDS 19(11): 1207-1214. 2005.

Judd A et al. Incidence of hepatitis C virus and HIV among new injecting drug users in London: prospective cohort study. BMJ, November 13^th, 2004.

Scottish Affairs Committee (1994): Drug Abuse In Scotland, First Report: Volume 1, HMSO, 1994.

Turnbull P et al: Drug Use In Prison, AVERT, 1994.