The development of the HIV epidemic in Karonga District, Malawi

Trends and measurement of HIV prevalence in northern Malawi

BACKGROUND

Most data on HIV prevalence in Malawi come from antenatal clinic (ANC) surveillance and are, therefore, subject to bias.

OBJECTIVES

HIV prevalence and risk factors were measured using population-based data to assess the accuracy of ANC surveillance and changes in prevalence and risk factors for HIV over time.

METHODS

HIV prevalence was measured in 1988-1993 and 1998-2001 in community controls from case-control studies of mycobacterial disease in Karonga District, Malawi. ANC surveillance studies in the district began in 1999.

RESULTS

Age and area-standardized HIV prevalence in women aged 15-49 years in the community was 3.9% in 1988-1990, 12.5% in 1991-1993 and 13.9% in 1998-2001. For men, HIV prevalence was 3.7%, 9.2% and 11.4% in the same periods. In 1988-1993, HIV positivity was associated with occupations other than farming, with increased schooling and being born outside Karonga District. In 1998-2001, non-farmers were still at higher risk but the other associations were not seen. The age- and area-adjusted HIV prevalence in the ANC in 1999-2001 was 9.2%. The underestimate can be explained largely by marriage and mobility. Reduced fertility in HIV-positive individuals was demonstrated in both ANC and community populations. A previously recommended parity-based adjustment gave an estimated female HIV prevalence of 15.0%.

CONCLUSIONS

HIV prevalence has increased and continues to be higher in non-farmers. The increase is particularly marked in those with no education. ANC surveillance underestimated HIV prevalence in the female population in all but the youngest age group. Although there were differences in sociodemographic factors, a parity-based adjustment gave a reasonable estimate of female HIV prevalence.

Highly divergent HIV type 1 group M sequences evident in Karonga District, Malawi in early 1980s

Six divergent HIV-1 partial env and gag genome sequences have been characterized in five subjects in Malawi, from whom blood spot samples were collected between 1982 and 1989, at the time that the AIDS epidemic there was starting. These sequences could not be classified with any of the recognized subtypes or circulating recombinant forms of HIV-1. They showed no consistent and/or supported associations with other subtypes by either env or gag gene phylogenetic analysis. Their genetic distances from defined subtypes suggest that they may be diverse subsubtype C viruses or, alternatively, that they may have mosaic genomes. Bootscanning analyses are consistent with their being mosaic viruses. These sequences highlight early HIV-1 diversity in a population otherwise dominated by subtype C.

The long-term impact of HIV and orphanhood on the mortality and physical well-being of children in rural Malawi

OBJECTIVE

To assess the influence of maternal HIV status and orphanhood on child mortality and physical well-being.

DESIGN

Retrospective cohort study with > 10 years of follow-up.

METHODS

From population-based surveys in Karonga District, Malawi in the 1980s, 197 individuals were identified as HIV-positive. These individuals and 396 HIV-negative individuals matched for age and sex, and their spouses and offspring, were sought in 1998-2000.

RESULTS

All but 11 of the index individuals were traced, identifying 2520 offspring; of these, 1106 offspring were included in analyses. Among those with HIV-positive mothers, mortality was 27% [95% confidence interval (CI), 17-38] in infants (1-30 days), 46% (95% CI, 34-58) in those under 5 years and 49% (95% CI, 38-61) in those under 10 years. The corresponding figures for those with HIV-negative mothers were 11% (95% CI, 8-13), 16% (95% CI, 13-19) and 17% (95% CI, 14-20). Death of HIV-positive mothers, but not of HIV-negative mothers or of fathers, was associated with increased child mortality. Among survivors who were still resident in the district, neither maternal HIV status nor orphanhood was associated with stunting, being wasted, or reported ill-health.

CONCLUSIONS

Mortality in children under 5 years is much higher in children born to HIV-positive mothers than in those born to HIV-negative mothers. With 10% of pregnant women HIV-positive, we estimate that approximately 18% of under-5 deaths in this population are attributable to HIV. Most of the excess is attributable to vertical transmission of HIV. Our findings suggest that, in terms of physical well-being, the extended family in this society has not discriminated against surviving children whose parents have been ill or have died as a result of HIV/AIDS.

Early evolution of the human immunodeficiency virus type 1 subtype C epidemic in rural Malawi

We have tracked the early years of the evolution of the human immunodeficiency virus type 1 (HIV-1) epidemic in a rural district of central east Africa from the first documented introductions of subtypes A, D, and C to the present predominance of subtype C. The earliest subtype C sequences ever reported are described. Blood samples were collected on filter papers from 1981 to 1984 and from 1987 to 1989 from more than 44,000 individuals living in two areas of Karonga District, Malawi. These samples included HIV-1-positive samples from 200 people. In 1982 to 1984, HIV-1 subtypes A, C, and D were all present, though in small numbers. By 1987 to 1989, 152 (90%) of a total of 168 sequences were subtype C and AC, AD, and DC recombinants had emerged. Four of the subtype C sequences from 1983 to 1984 were closely related and were found at the base of a large cluster of low diversity that by the late 1980s accounted for 40% of C sequences. The other two early C sequences fell into a separate and more diverse cluster. Three other clusters containing sequences from the late 1980s were identified. Each cluster contained at least one sample from a person who had recently arrived in the district. From 18 HIV-1-positive spouse pairs, 12 very closely related pairs of sequences were identified. We conclude that there were multiple introductions of HIV-1 with limited spread, followed by explosive growth of a subtype C cluster, probably arising from a single introduction in or before 1983.

Long-term follow-up of HIV-positive and HIV-negative individuals in rural Malawi

OBJECTIVE

To measure the effect of HIV on survival in rural Africa.

DESIGN

A retrospective cohort study with more than 10 years follow-up.

METHODS

Individuals with known HIV status in the 1980s were identified from previous population surveys in Karonga District, northern Malawi. Follow-up studies were conducted in 1998-2000 to trace 197 HIV-positive and 396 age-sex-matched HIV-negative individuals and their spouses.

RESULTS

Information was obtained on all but 11 index individuals. Half (302) were found and the others were reported to have died (161) or to be alive outside the district (119). Ten year survival was 36% in the HIV-positive cohort and 90% in the initially HIV-negative cohort. The death rate was 93.3 per 1000 person-years in the HIV-positive individuals, and 11.3 in the initially HIV-negative individuals. Survival time since the initial test in HIV-positive individuals decreased with age, but relative survival, compared with HIV-negative individuals, was similar across age groups. The effect of HIV on survival was similar in men and women. Spouses of HIV-positive individuals had four times the mortality rate, and among survivors, four times the HIV prevalence, of spouses of initially HIV-negative individuals.

CONCLUSION

HIV-infected individuals had very high mortality rates, but one-third were still alive at 10 years. This is consistent with median survival from seroconversion being similar to that found in developed countries before antiretroviral therapy. Mortality rates in HIV-positive individuals increased with age, but relative mortality changed little with age.