Investigators in the Cameroon have found an association between overnight travel from home and being HIV-positive. The study, published in the January 1st edition of the Journal of Acquired Immune Deficiency Syndromes, also found that geographic mobility in men was associated with a higher number of one-off sexual encounters and a greater number of sexual partners. However, investigators failed to find as distinct an association between travel and HIV-status in women. The study confirms that the link between mobility and HIV infection is not confined to rural populations, and that it is a critical feature of urban HIV epidemics too.
Throughout history, travel has been associated with epidemic disease. Trade and migration is thought to be one of the reasons explaining the waves of bubonic plague which swept across Europe and Asia in the middle ages and early modern period, and the movement of armies in the early 16th century has been suggested as an explanation for the rapid spread of syphilis across Europe.
HIV has taken advantage of human geographic mobility, and a little over 20 years after the virus was first recognised it is now present in every region of the world with an estimated 42 million people living with the infection.
Studies have already looked at the relationship between the spread of HIV and rural migration and travel in Africa. However, the role of travel from urban centres and the spread of HIV in Africa had not been explored, accordingly, investigators set out to investigate the relationship between geographic mobility, sexual behaviour and HIV infection in Yaounde, the administrative capital of Cameroon. The study was conducted in 1997, at which time the HIV prevalence amongst pregnant women was 5.5%, and 37% amongst sex workers.
A total of 896 men and 1,100 women were included in the study. During a home visit, they were tested for HIV and other sexually transmitted infections, and were asked the number of times they had traveled away from home in the past year. Individuals were also interviewed about their sexual behaviour, including how many sexual partners they had had in the last twelve months, if they had had sex with a person other than their spouse, if they had paid for sex, and if they had used condoms. Demographic data were also gathered, including age, marital status, and education and employment details.
Travel away from home was divided into three categories: no travel; less than 31 days travel; and, over 31 days travel. Investigators compared the sexual behaviour of individuals in these categories.
The median age for men was 26 years, and 25 years for women. The overwhelming majority of men (68%) and women (85%) had received only a primary education. A clear majority of men (54%) were in employment, as were 30% of women.
Geographic mobility characterised both men and women, with a little under 73% of men and almost 68% of women reporting at least one overnight trip in the previous year. The median number of trips for men was three and for women two, although over a fifth of men and a little over 12% of women reported over ten overnight trips.
Individuals traveling were more likely to have been born outside Yaounde and to have received a post-primary education.
Univariate analysis showed that amongst men, the prevalence of HIV infection increased with travel. The prevalence was 1.4% amongst men declaring no travel, 3.4% for men traveling for less than 31 days, and 7.6% for men with over 31 days travel. This association remained significant after multivariate analysis controlling for age and other demographic factors and sexual behaviour.
For women, however, the pattern was less clear, with similar levels of HIV infection recorded for both mobile and non-mobile women (6.9% versus 9.8%, p>0.1).
Travel was also linked to distinct patterns of sexual behaviour. Unmarried men reporting over 31 days of travel were more likely to report more than one sexual partner in the last 12 months than men reporting no travel (62.5% versus 30%, odds ratio 3.3, 95% CI: 2.0 – 5.40). A similar trend was noted when the analysis was restricted to married men. Further, men were more likely to report sex with a person other than their spouse the greater their duration of travel: 35% of men with no travel reported a non-spousal partner versus 57.6% of men away form home for under 31 nights, and 63.5% of men away for 31 nights or more (odds ratio 3.3 and 3.9). What’s more, married men traveling for more than 31 nights had more one-off sexual encounters than men reporting no travel (19% versus 6%). Investigators were able to find no significant difference between the three groups in respect of condom use or paying for sex.
Different patterns emerged for women. Fewer unmarried women than men reported more than one sexual partner (21.7% versus 49.1%). However, as with men, women who traveled away from home for more than 31 days were more likely to report multiple sexual partners (odds ratio 2.7, 95% CI: 1.45 – 4.9). Travel did not appear to alter the sexual behaviour of married women, however, with married women traveling 31 days or more reporting no more sexual partners than married women who did not travel at all. Like men, there was no difference between the three travel categories as regards condom use and the exchange of money for sex.
"The present study" state the investigators, "provides evidence that mobility may be an important feature of the HIV epidemic in the Cameroon. Not only was the duration spent away from town strongly associated with HIV infection for men, but also more risky sexual behavior for mobile individuals was associated with the duration of absence."
The association between mobility, risky sexual behaviour and HIV infection amongst married men meant that married women were at greater risk of acquiring HIV from their husbands.
The investigators conclude, "researchers often focus on mobile rural persons as bridge populations in the spread of the virus [HIV] from urban to rural areas. Our findings suggest that, equally in town, the HIV epidemic can be continuously refueled by extraurban mobility. Mobile urban people also contribute to the spread of virus at both ends of the migratory scale."
Further information on this website
Low incidence of nevirapine resistance seen in Cameroon women given drug for MTCT - news story
Lydie N et al. Mobility, sexual behavior, and HIV infection in an urban population in Cameroon. JAIDS 35: 67 – 74, 2004.