Volume 5 No 22; 06 June 2011
On 5 June 1981, five young 'homosexual' men in Los Angeles were reported to have Pneumocystis carinii pneumonia and case histories suggesting a 'cellular-immune dysfunction related to a common exposure' . These men were the first reported cases of acquired immunodeficiency syndrome (AIDS). Ten days later, the first UK case of as reported in a young man with haemophilia followed by further reports of AIDS among homosexual men. These first reports, prompted the creation of the UK's AIDS surveillance scheme in 1982 to monitor Kaposi's sarcoma and opportunistic infections. Once the virus that causes AIDS (known today as the human immunodeficiency virus - HIV) was identified and a diagnostic antibody test developed in 1984, surveillance was extended to include laboratory diagnoses of HIV.
Thirty years on, highly effective treatment where it is widely available, has transformed HIV infection from a fatal to a chronic manageable infection. Today, people diagnosed and treated in the early phase of HIV infection can expect a normal life span with much fewer side effects compared to the earlier drug regimens. The ongoing high rates of HIV diagnoses and fewer deaths from AIDS has resulted in a steady rise in the number of people living with diagnosed HIV. In 2012, it is estimated that the number of people living with HIV in the UK (diagnosed and undiagnosed) will reach 100,000 (assuming a steady increase of 4,000 additional individuals seen for care and a constant in the proportion undiagnosed [26%]). If the estimated 3,800 UK-acquired HIV cases in 2010 had been prevented, over £32 million annually or £1.2 billion over a lifetime in costs would have been saved and the impact of HIV on the most affected communities substantially reduced.
To date, there have been over 115,000 people diagnosed with HIV in the UK, of whom over 27,000 have developed AIDS and almost 20,000 have died. The development of a HIV test in 1984 led to the first peak in HIV diagnoses in 1985 (2,935). This was accompanied by a rapid rise in AIDS cases and deaths in the late 1980s through to the early 1990s (Figure 1). AIDS diagnoses peaked in 1994 (1,872), and deaths in 1995 (1,723) with both then declining. The availability of highly active antiretrovial therapy (HAART) was responsible for this rapid decline in AIDS diagnoses and deaths and the relatively low but constant numbers since the late 1990s. In the initial years of the epidemic, diagnoses were predominately among persons who acquired their infection through the acquisition of blood or tissue products, injecting drug use (IDU) and sex between men. In later years, while men who have sex with men (MSM) remain the major risk group, heterosexually acquired infections have also become of increasing public health importance.
There have been major advances in the management of HIV since the infection was first recognised 30 years ago, transforming the condition from a death sentence to a manageable chronic illness where highly effective treatment is available. However, the benefits of treatments rely on the early diagnosis of the infection. In 2010, over half of all people reported with HIV infection in the UK were diagnosed with a CD4 count of less than 350, below the recommended threshold for beginning HIV treatment. Furthermore, over a quarter of those infected with the virus remain unaware of their infection and risk transmitting the virus to their sexual partners. These data have been the driving force behind policies to expand HIV testing in high prevalence areas and the need to intensify prevention efforts to reduce UK acquired infections.
Figure 1: Annual new HIV and AIDS diagnoses and deaths: UK, 1981-2010
Infections acquired through sex between men
MSM have remained the group most disproportionately affected by and at risk of HIV infection through the three decades. A cumulative total of over 51,500 HIV new diagnoses have been reported in this group. Over 2,000 diagnoses had already been reported by 1985 and despite the plateau in the late 80s and 90s, where, on average, 1,620 cases were reported annually, numbers have since risen year on year (figure 2). After an almost doubling in the last decade, 2010 saw the largest ever annual number of new HIV diagnoses among MSM (3,080) (2). HIV prevalence remained high at approximately 5% (4-6%) among MSM each year since 2002 with a prevalence rate of 9% (7-11) in London.
Figure 2: Annual New HIV diagnoses among men who have sex with men: UK, 1981-2010
A combination of surveillance systems and techniques suggest that the upward trend in new HIV diagnoses seen in recent years among MSM is likely due to a rise in HIV transmission. Testing with Recent Infection Testing Algorithm (RITA) suggests that a quarter of MSM newly diagnosed in 2010 probably acquired their infection 4-5 months prior to diagnosis with higher recent rates in younger ages (32% in those aged from 15 to 24 years). Additionally, median age and CD4 count at diagnosis among MSM have remained steady since 2001 (overall: 35 years and 398 cells/mm3, respectively). A final piece of evidence comes from HIV incidence estimates from the multiparameter evidence synthesis (MPES) based model, which suggests an increase in HIV incidence in MSM from 0.5% (credible intervals 0.1%-0.8%) in 2002 to 0.9% (0.5%-1.3%) in 2007 .
Infections acquired through heterosexual transmission
Infections acquired heterosexually were infrequent during the early part of the epidemic, but rapidly increased from 1999 and peaked in 2004 at 4,880 diagnoses. A cumulative total of over 53,000 diagnoses have been reported among people infected heterosexually, with the large majority of infections diagnosed among those born abroad (mostly in sub-Saharan Africa) and who probably acquired their infection in their country of origin. However, since 2003, there has been a sharp decline in diagnoses in this group and in contrast, diagnoses among heterosexuals who most likely acquired their infection in the UK have risen in recent years (from 210 in 1999 to 1,150 in 2010) (figure 3).
Figure 3: Annual new HIV diagnoses acquired heterosexually: UK, 1981-2010
Infections acquired through injecting drug use (IDU)
Transmission of HIV through injecting drug use (IDU) was recognised worldwide early in the epidemic. A cumulative total of 5,500 people who most likely acquired their infection though IDU have been diagnosed with HIV in the UK to date. There is no doubt that the magnitude of the epidemic through IDU would have been more significant had it not been for the successful introduction of needle exchange programmes (NEP) in 1985. Following an initial rapid rise, new diagnoses cases in this group reached an annual peak in 1986 (415) and began to fall substantially thereafter and have remained steady (figure 4). Over half of diagnoses among persons who acquired their infection through IDU in recent years, were born abroad and acquired their infection prior to residing in the UK. The sustained availability of NEP has meant that HIV prevalence remains below 1-2% in this population . This is in striking contrast with countries, particularly within Eastern Europe, which have not implemented harm reduction interventions and are witnessing prevalence rates of over 50% among IDU and 1% in the general population driven primarily by uncontrolled IDU.
Infections acquired through mother to child transmission
Mother to child transmission of HIV is relatively uncommon in the UK with 1,983 new diagnoses to date. The implementation of routine antenatal testing for HIV in 2000 has promoted the early diagnosis of HIV in HIV positive pregnant women and the subsequent availability of prophylactic treatment has reduced the risk of mother to child transmission (figure 4). Unlinked anonymous serosurveillance data indicated that 0.2% of pregnant women were infected with HIV in 2009. The slight increase observed between 2002 and 2006 is largely due to mothers born abroad and gave birth in a country with a high prevalence of HIV.
Infections acquired through blood and tissue products
By 1985, 1,071 diagnoses had been reported among persons who acquired HIV through blood/tissue products, accounting from more than half of all infections ever reported in this group. The large majority were among people with haemophilia (1,039) . That same year in October, with the availability of diagnostic tests to identify HIV, the Blood Transfusion Service began screening all blood donations. This led to an immediate impact on infections acquired through this route with a drop of diagnoses from 790 in 1985 to 171 in the following year (figure 4). Since 1987, there have been, in total, 722 diagnoses in this group and179 of these were among individuals with haemophilia, the vast majority of these later diagnoses of infections acquired prior to 1985. Since 2002 all infections acquired through receipt of blood/tissue products were acquired outside of the UK.
Figure 4: Annual new HIV diagnoses by prevention group: UK, 1981-2010
1. CDC. Pneumocystis pneumonia – Los Angeles. MMWR 1981;30:250-2. Available at http://www.cdc.gov/hiv/resources/reports/mmwr/1981.htm.
2. Largest ever annual number of new HIV diagnoses in MSM: UK data for 2010. Health Protection Report 2011; 5(12), infection reports. Available at http://www.hpa.org.uk/hpr/archives/2011/hpr1211.pdf
3. Presanis AM De Angelis D, Goubar A, GIll ON, Ades AE.. Bayesian evidence synthesis for a transmission dynamic model for HIV among men who have sex with men. Biostatistics 2011, Epub ahead of print http://biostatistics.oxfordjournals.org/content/early/2011/05/04/biostatistics.kxr006.long
4. Health Protection Agency. Shooting up. Infections among injecting drug users in the UK 2009. An update: November 2010. London: HPA, 2010. Available at http://www.hpa.org.uk/Publications/InfectiousDiseases/BloodBorneInfections/