Since 1999 the number of reports of new diagnoses of infections attributed to heterosexual sex have outnumbered other routes of infection and are now the major source of new infections. By the end of June 2005 there had been a total of 68,712 infected individuals reported in the UK. 36,671 (53%) of these were infected heterosexually.

The majority of the heterosexual HIV infections diagnosed in the UK are acquired abroad by people HIV-infected before moving to the UK, though HIV infection is also contracted heterosexually by individuals from the UK working or travelling abroad.

Of all diagnoses of heterosexually acquired infections made during 2002, 70% are attributed to infection in Africa. However, the numbers of UK diagnoses of infections heterosexually acquired in Asia and in Latin America/Caribbean has risen in the latter part of the 1990s, while those from North America, Europe, and Australasia have increased more slowly, and decreased relative to the total of infections. (see chart).

 (Source: HPA)

Reports received to the end of June 2002 showed that 52% (305) of the total of 590 infections reported as acquired in Asia were associated with Thailand, often affecting individuals visiting that country from the UK for business or tourism. Diagnoses of infections acquired in Latin America/Caribbean increased overall from a cumulative total of 320 at the end of March 2001 to 480 by the end of December 2002.

Bridging communities

During the early years of the epidemic it was thought that groups recognised as being at high risk of HIV infection, such as bisexual men and injecting drug users, would provide a ‘bridge’ for the virus to cross into the general population through heterosexual sex. In the UK this route does not seem to have had a great impact on the spread of HIV. Annually there have been fewer than 90 new diagnoses of infections acquired in this way throughout the last decade, and the number has been going down, not only as a proportion of the total, but in absolute terms. Overall 4.4% (1229/27,902) of heterosexually infected individuals diagnosed by the end June 2005 were categorised as infected through contact with a partner classified as ‘high risk’ (see chart below).

(Source: HPA)

HIV transmission within UK

In addition to the sharp rise in HIV diagnoses in people who have acquired their HIV heterosexually outside the UK, there has also been a rise in the number of new diagnoses of HIV infections acquired heterosexually  in the UK, from a partner also presumed to have been infected heterosexually.

Most of the rise in diagnoses is attributable to infections acquired through heterosexual contact in the UK, with individuals themselves  infected heterosexually outside Europe. Altogether 5.8% of heterosexual infections come into this category, though 6.4% of heterosexual infections in 2004 were of people infected in the UK by partners infected abroad. For 79% of this group (576/731) the partner’s infection was attributed to heterosexual contact in sub-Saharan Africa.

The number of infections recorded where both partners acquired their HIV in the UK has increased only slightly and has decreased as a proportion of those infected. It stood at about 70 infections in 2004, or just 1.7% of the heterosexual total for that year, and totals 798 out of 27,902 heterosexual infections recorded, or under 2.9% of the total.

More women diagnosed than men

More heterosexually acquired infections have been diagnosed in women than in men. By the end of June 2005 the number of heterosexually infected women diagnosed was 16,185 and the number of men was 10,486 (60% women). For the last complete year, 2004, 1412 men and 2452 women (63% women) were diagnosed.

In those infected through contact with members of high-risk groups the number of diagnoses in women is much higher than men. This is because those in the high-risk groups are predominantly male. There are also more females than males among those recorded as heterosexually infected in Africa, and among those infected heterosexually in the UK by a partner infected heterosexually outside Europe. The female predominance overall has been contributed to by an increased uptake of testing as a result of initiatives to improve the rates of maternal antenatal diagnosis. It may also reflect the differing attitudes to health care between men and women.

Increase in heterosexuals receiving care

The annual survey of prevalent diagnosed HIV infections (SOPHID) collects information for every patient seen for HIV-related treatment and care in the previous year. It therefore reflects current prevalence whereas the cumulative reports referred to above also include people who have died and people who may later have left the country. Largely as a result of the increasing numbers of diagnoses of heterosexually acquired HIV, for England and Wales reports to the SOPHID survey of individuals with heterosexually acquired HIV infection receiving care rose from 5357 in 1999 to 15998 in 2003 - a threefold increase.

The focus of the epidemic in the UK is in London and the south-east of England, but the heterosexual epidemic is less concentrated on London than the gay one, possible due to dispersal of asylum seekers. All areas of England and Wales except for London, the north-west and the south-west have more heterosexuals receiving care than gay men (see chart).

Of those heterosexually infected, 8248 (51%) lived in the London region - compared with 8831 (57%) gay men - and a further 11% elsewhere in the south east.

Of those seen for HIV-related care in 2003 and who were resident in London, 47% were white, 37% were black African and 16% other ethnic groups such as Afro-Caribbeans, South Asians and Orientals. Outside London 57% were white, 34% black African and only 9% from other ethnic groups.

Only those who have their infection recognised early in the course of disease can benefit fully from interventions that can improve their prognosis.

Results from the UAPMP survey of genitourinary clinic attendees in 2003 found that the prevalence of HIV infection among heterosexual GUM clinic attendees was 1.53% in London, compared with 20.2% among gay men, and 0.42% outside London (excluding Scotland), compared with 3.5% in gay men.

Since the UAPMP does not record the ethnicity of the people whose anonymous samples are surveyed, this reflects HIV prevalence in the sexually-active heterosexual population generally. Prevalence among vulnerable groups like African is higher. A survey in 2001 found that among heterosexuals born in sub-Saharan Africa and attending London GUM clinics in 2000/2001, one in 21 men (4.75%) and one in 13 women (7.7%) was HIV-positive, compared to one in 428 men (0.23%) and one in 573 women (0.17%) born in the UK.

Of the heterosexuals with HIV infection, 50% had not had their infection diagnosed previously, with a slightly higher proportion of women than men undiagnosed. This is more than double the proportion of gay men turning up with undiagnosed infections (24%).

Of these previously undiagnosed GUM clinic attendees, 41% went away from their STI checkup without their HIV infection being diagnosed, compared with 27.5% of gay men.

Thus while gay male GUM clinic attendees are 15 times more likely to have HIV than heterosexual attendees, they are ‘only’ 7.5 times more likely to have undiagnosed infections, and ‘only’ five times more likely to have infections that remain undiagnosed after a GUM clinic visit.

Subtype B gets less common

The HPA reports of where infection was acquired are subject to some uncertainty since it is often the patient or clinician’s best guess as to where they were infected that gets recorded on the monitoring form.

One independent indicator that heterosexuals in the UK are acquiring HIV that at least originated in Africa is that the proportion infected with HIV subtype B – the most common in the developed world - has fallen significantly in recent years, according to data presented to the HPA’s annual scientific conference in 2002.

Gary Murphy told delegates that between 1997 and 1999, the proportion of subtype B new HIV infections amongst heterosexuals fell to less than 5% of the total, while the number of heterosexuals found to be recently infected with non-B subtypes increased, in particular HIV subtype A (found, more than anywhere else, in Kenya), subtype C (found throughout eastern and southern Africa) and subtype AG (a ‘cross’ between A and a virus found in central west Africa).

Dr Murphy said it was not possible to determine if the infections had happened in the UK, but researchers suspected that the overwhelming number of heterosexual infections were acquired outside the UK, particularly in sub-Saharan Africa.

Whilst the number of new subtype B infections fell overall amongst heterosexuals regardless of sex, they remained disproportionately concentrated amongst men.

Some researchers believe that the fact that heterosexual men are somewhat more likely than women to be infected with subtype B is evidence of covert homosexual behaviour not admitted at the time of HIV testing.

Pregnant women

The UAPMP of pregnant women found that in 2003 0.45% of all pregnant women in London had HIV (one in 222), and 0.07% outside London (one in 1429).

It was estimated that 88% of pregnant women in London and 95% outside London had their HIV infections diagnosed prior to giving birth – a huge improvement from the last time this was reported in this manual, in the year 2000, when 82% in inner London, 65% in outer London, and 56% in the rest of England and Wales had had their infection diagnosed prior to giving birth. The Government set a target of 90% uptake of HIV testing by the end of 2002.

(Source: Tookey, see references below))

In 2003, the prevalence of HIV was highest in inner London with 0.56% (one in 179 women) who gave birth to live-born infants in this area being infected with HIV. In the same time period in outer London, 0.36% (one in 277 women) gave birth to live-born infants. This was a substantial rise since 2000. Within London, the prevalence varied considerably according to maternal health authority of residence and was highest in Lambeth Southwark and Lewisham. I

Outside London, the prevalence of HIV infection among women giving birth to live-born infants has remained lower than the rate for the population as a whole.

Estimates of the prevalence of HIV in pregnant women have also been made for health authorities in the UK not covered by the UA programme. These estimates have been derived using available data from the dried blood spot programme and the survey of prevalent HIV infections diagnosed (SOPHID).

National targets that involve the offer and recommendation of an HIV test to all pregnant women throughout England were set in 1999. It was intended that by increasing the uptake of antenatal HIV testing to 90%, and by increasing the proportion of HIV infections diagnosed prior to delivery to 80%, an 80% reduction in the proportion of children acquiring HIV infection from their mothers should have been achieved by December 2002. These targets have now been met outside London and are almost met in London, though were not met by 2002.

In 2004, of the 600 women known to be HIV-positive during pregnancy, 552 were already diagnosed before the current pregnancy, and 48 diagnosed during antenatal care.

Children

Since the beginning of the epidemic up till June 2005, 6255 children have been reported to have been born in the UK to HIV-infected mothers, of whom 1362 (20.5%) became infected with HIV before or during birth, or as infants. Another 1404 have yet to have their HIV serostatus determined, but as these are all children born recently, most will prove to be uninfected.

Source: HPA. See http://www.hpa.org.uk/infections/topics_az/hiv_and_sti/hiv/epidemiology/epidemiology.htm#mtoc

The transmission rate has improved over time. In 2003, assuming the same transmission rate, of 819 babies born to mothers with HIV, about 170 babies would have acquired HIV in the absence of prevention methods. In fact, only 35 (4.2%) did. It is estimated that HIV infection could have been prevented in half of these 35 infected babies if every pregnant women with HIV had her infection detected before delivery. Of the HIV-positive women giving birth in England in 2001, 70% lived in London and 77% were born in sub-Saharan Africa.

The proportion of diagnoses of HIV that are due to mother-to-child transmission has stayed remarkably constant over time, varying from 1.8% to 3.7% of the total since 1992, despite the proportion of HIV diagnoses that are among women increasing during that time from 18% of the total to 42%. This reflects both increased detection of HIV infection in pregnant women before delivery, and improvements in the use of antiretroviral therapy and delivery methods to prevent mother-to-child infection.

Of infected children, 833 (61%) were born in London whereas of those known to be uninfected, only 56% did. Of the 1362 children with HIV, 255 (19%) are known to have died.

About 10% of children in the UK and Ireland born to HIV-infected women were born abroad, so the sum total of of children reported was 6604, of whom 1387 (21%) were known to have HIV, with another 21% undetermined. Of these, 55% were reported from London, 28% from the rest of England and 11% from the Republic of Ireland.

By the end of 2003 it was known that about 150 of these children were under five years old, 280 were aged 5-8, 250 aged 9-12, and 130 were 13-15. Another 75 teenagers aged 16-19 had acquired HIV when they were born, so altogether there are 205 young people who have reached the age of adolescence, having lived with HIV throughout their childhood.

Another 360 teenagers aged 15-19 have acquired HIV through sexual transmission or injecting drug use.

By 2002, about 70% of children were taking antiretrovirals. Mortality rates declined by 80% and progression to AIDS by 50% between 1997 and 2002.

References

Ades AE, Walker J, Botting B, Parker S, Cubitt D, Jones R. Effect of the worldwide epidemic on HIV prevalence in the United Kingdom: record linkage in anonymous neonatal seroprevalence surveys. AIDS 13: 2437-2443, 1999. 

HPA. AIDS and HIV infection in the United Kingdom: monthly report. HIV infection in women giving birth in the UK – trends in prevalence and proportions diagnosed to the end of June 2000. Commun Dis Rep CDR Wkly [serial online] 2001 [cited 11 April 2002]; 11 (8): HIV/STI. Available from http://www.phls.org.uk/publications/cdr/archive/hivarchive.html

Duong T, Ades AE, Gibb D, Tookey P, Masters J. Vertical transmission for HIV in the British Isles: estimates based on surveillance data. BMJ  319: 1227-1229, 1999.

Expert Group on Antenatal HIV Targets. Targets aimed at reducing the number of children born with HIV: report from an Expert Group. London: Department of Health, July 1999.

Tookey P. Obstetric and paediatric HIV surveillance data from the UK and Ireland: Data to the end of June 2005. Institute of Child Health, July 2005. Powepoint presentation at: http://hpa.org.uk/infections/topics_az/hiv_and_sti/hiv/epidemiology/files/NSHPC_slide_set_July_2005.ppt