But
HIV prevalence in populations is not related in any simple way to the average
number of sexual partners people have. Differences in HIV prevalence between
countries or ethnic groups in the same country cannot be explained this way.
One
survey, for instance, found that men in Thailand and in Rio de Janeiro actually
had a higher average number of lifetime sexual partners than men in four
African countries (Tanzania, Kenya, Lesotho and Zambia), and women had low
numbers of partners in any country, with very few having more than five a year.1
Similarly,
Daniel Halperin2,3
compared three mid-1990s surveys of men in Thailand,
the US and Uganda. He found that the
proportion of men who said they had had more than ten lifetime sex partners was
over 60% in Thailand, over 40% in the USA, and just over 20% in Uganda; yet HIV
prevalence among men in those countries was respectively 2.2, 1 and 18% at
the time the surveys were conducted.
Why,
then, have the countries of Africa and especially southern Africa, an area with
2% of the global population but a third of the world’s HIV-positive people,
ended up with HIV prevalence an order of magnitude greater than any other
countries in the world?
Attempts
to explain southern Africa’s HIV prevalence
struggle to find anything unique about the area. Condoms in Africa
have historically been used in a minority of sexual encounters4
but, except as a result of campaigns targeted at sex workers and their clients,
this is also the case throughout much of the world.5
Surveys have found very high levels of sexually transmitted infections (STIs)
amongst African men and women, but untreated and especially asymptomatic STIs
are almost as common in other countries.6
Differences
in the proportion of men who are circumcised may explain some of the
differences between, for instance, southern and western Africa
or between ethnic groups in single countries.7
It does not explain why countries outside Africa where circumcision is
uncommon, such as Thailand or southern Europe, have not seen generalised
epidemics along African lines, given that some risk behaviours (for instance,
the proportion of men who pay for sex) are actually higher in those countries.
There
is one pattern of sexual behaviour, however, that is much more common in Africa
- and especially in southern Africa - than
anywhere else in the world. Martina Morris of the University
of Washington compared relationship
patterns in countries ranging from South Africa
to Uganda to patterns in Thailand and the US and found that having more than
one regular partner at the same time was common in African countries.8
For
instance, she found that Ugandan men reported fewer lifetime sexual partners
than Thai men, but while the Thais usually combined one primary relationship
with one-off encounters with sex workers, Ugandan men often had two or
sometimes three long-term sexual relationships. In some groups, this has been
codified into overt polygamy, but the pattern was more often that a man would
have a wife but would also have a long-standing girlfriend, separated either
geographically (for instance a wife in the home village and a girlfriend in the
city, or vice versa) and temporally (for instance, a girlfriend during work
hours and a wife at weekends).
In
a number of cultures it has been common for wealthier men to keep both a wife
and a mistress, but this has only ever applied to a minority of the population.
Men who cannot afford two women might visit sex workers, but one-off or
occasional casual sex encounters do not have the same potential for spreading
HIV. The length of concurrency in Africa (where
concurrent relationships overlapping for more than a year are common) is one
difference with other cultures. The other, crucial difference is that, while in
other cultures only men would tend to have long-term, concurrent relationships,
research suggests that in certain African countries a significant minority of
women do so too.
Carael,
bringing together a number of studies1
found that 13% of men in Kenya,
22% in Lusaka, Zambia,
36% in Ivory Coast and 55%
of men in Lesotho
had long-term, concurrent sexual relationships with at least two women. The
highest proportion of men operating the same lifestyle anywhere else surveyed
was in Rio de Janeiro, where 7% had concurrent
relationships, but in four Asian locations– Thailand,
Singapore, Sri Lanka and Manila
in the Philippines
– no more than 4% of men had concurrent relationships.
Women
had a fairly accurate idea of whether their men were ‘seeing someone else’ in
some places. When asked, the proportion of women in Thailand,
Manila and Lusaka
who were asked if their man had another long-term relationship agreed with the
actual total to within a few per cent. Women in Ivory
Coast, Tanzania
and Kenya thought their men
were less faithful than they actually were - while women in Lesotho underestimated the scale of
unfaithfulness going on. But in no case did the women over- or underestimate
‘concurrency’ in their men by more than 25%.
However,
in order for concurrent relationships to amplify HIV transmission in
heterosexual epidemics, women have to be involved in them too; otherwise a
chain of infection, from man to woman to man and so on, cannot be sustained.
The proportion of women who had concurrent, long-term partnerships with more
than one man was lower than the proportion of men who had them. But it was
still about an order of magnitude higher in African countries than in other
countries. Eleven per cent of women in Lusaka, Zambia, 9% in Tanzania,
and no less than 39% in Lesotho
had long-term relationships with two or more men, compared with 3% in Manila, 1% in Sri Lanka
and less than 1% in Rio and the other Asian
countries surveyed.
The degree to which women had concurrent
relationships was greatly underestimated by their male partners; in all but one
of the countries surveyed, the proportion of women involved in long-term
concurrent relationships was more than double the proportion of men who thought
their woman was involved in one.