A new approach developed by scientists at the Health Protection Agency indicates that around 31% of African heterosexuals diagnosed with HIV in the UK may have acquired their infection in the UK, as opposed to the 10% indicated by current methods. Moreover, UK infections among African people appear to have been rising in recent years.
The new method, analysing CD4 cell counts and the year a person arrived in the UK, is described in the September 24 issue of AIDS.
The question of where HIV-positive African people in the UK acquired their infection is important for the UK’s HIV prevention policy. If there is good evidence of new infections occurring in the UK, then HIV prevention work with African communities in the UK is more important than if the vast majority of HIV-positive Africans had HIV before they arrived in the country.
When analysing data on new HIV diagnoses, the HPA’s current method for assigning the most likely country of infection relies on information given by the patient to the clinician or health adviser at the time of diagnosis. But individuals may not always be completely frank about their sexual behaviour. Their sexual history may be complex, spanning a number of years and countries, making it difficult to pinpoint when an infection is most likely to have occurred.
In 2009, closer examination of the medical and sexual histories of 263 African adults recently diagnosed with HIV in London suggested that between 25% and 35% could have been infected in the UK.
Now, Brian Rice and colleagues have developed a technique which uses a person’s CD4 cell count at the time of diagnosis in order to estimate the year in which they are likely to have been infected, and compares that to the year in which they arrived in the UK.
Their analysis looked at adults diagnosed between 2004 and 2010 in England, Wales or Northern Ireland who were born abroad and thought to have been infected through heterosexual contact. This therefore included people of all ethnicities, although 85% were black African.
Of 18,911 adults who met this criteria, there were both CD4 and year of arrival data available for 10,612 people.
Using the standard method, based on sexual histories and clinician reporting, 11.3% of heterosexual adults (of all ethnicities) acquired HIV in the UK. But using the new method, the estimate rose to 32.5% (range of estimates: 22% to 44%).
Now looking only at black African heterosexual adults, according to the standard method, 9.7% acquired HIV in the UK. The estimate from the new method was that 31.2% had done so (range of estimates: 21% to 43%).
The proportion of UK infections has risen in more recent years – among black Africans it has gone up from 24% in 2004 to 43% in 2010. The proportion of UK infections is higher in older people than in younger people.
The authors note that one limitation of their approach is that it is unable to account for individuals who were born abroad, are currently living in the UK and who acquire HIV while travelling overseas, perhaps to their country of birth.
Moreover, the Health Protection Agency has not yet decided whether this method of analysis will be used in future to inform their routinely published surveillance statistics.
But the authors conclude: “We have applied a new method to assign likely place of HIV infection that relies on the provision of objective, routinely collected surveillance data to identify communities most at risk of acquiring HIV heterosexually while living in the UK.”
They say that the method could be used in other countries with large numbers of diagnoses in migrant populations.
Finally, “Our findings highlight the need for improved targeted prevention efforts to reduce the transmission of HIV among black-African communities living in the UK.”
Previous research, conducted with different populations, has suggested that risky behaviours and HIV infections can sometimes become more common when people move to another country. For example, studies have been conducted with African and Caribbean migrants to the Netherlands, Central and Eastern European gay migrants to the UK and Mexican migrants to the United States.
Rice BD et al. A new method to assign country of HIV infection among heterosexuals born abroad and diagnosed with HIV. AIDS 26: 1961-1966, 2012.