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
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
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.