We have shown a marked shift from the usually observed pattern of socio-economic determinants of child mortality, in a population with high HIV prevalence and declining background levels of child mortality. In Karonga District in the 1990s we observed lower under-5 mortality in those whose fathers were traders or salaried workers compared to subsistence farmers or casual labourers, and lower mortality in those whose mothers had higher levels of education 
. In the current study, factors such as higher maternal education, improved housing, and source of income, were not strong predictors of lower child mortality when mortality from all causes was considered.
Under-5 mortality in this population was 85 per 1000 births, lower than the national average estimate from the 2004 DHS (133 per 1000),
but comparable with levels recorded in 2004 in neighbouring Tanzania (83 per 1000 births).
Adult HIV prevalence has been around 12% since 2000 in Malawi 
and in 2005 only 7% of HIV-infected mothers were estimated to have received ARV prophylaxis for the prevention of mother-to-child transmission.
Although the HIV epidemic is likely to have a severe impact on child mortality in Malawi, overall levels of mortality have steadily declined.
This can only be explained by a large decline in non-HIV related mortality, and with declining levels of background mortality, the relative impact of HIV is likely to increase.
The comparative analysis of risk factors for AIDS- and non-AIDS mortality revealed that the absent or weak associations of socio-economic factors with child mortality from all causes were explained by the differential distribution of AIDS and non-AIDS deaths in the population. Almost all AIDS deaths in children in this population are likely to have been caused by transmission of HIV from mother to child and the distribution of paediatric AIDS deaths is therefore likely to mirror the distribution of HIV infection in women of reproductive age. It is possible that women of higher socio-economic status are more likely to be HIV tested, and knowledge of the mother's HIV status may have influenced classification of the death, but only about one third of the AIDS deaths in those under 5 years were in those whose mothers were known to be HIV-infected.
In contrast to the 2004 Malawi DHS, in which children of mothers with secondary school education had approximately 40% lower infant mortality and 60% lower under 5 mortality,
maternal education in the study population was only weakly associated with all cause mortality in infants or children. Infants and children of mothers with secondary education had the highest rates of AIDS mortality and the lowest rates of non-AIDS mortality, but both trends were weak. Trends with paternal education were also weak, and differed in infants and children. In both age groups there were high death rates in those with unknown maternal education, reflecting high mortality among maternal orphans (not shown).
Measurement of economic status at the household level in this study included ownership of household assets and dwelling construction, adapted to the local setting. Such indicators have shown close association with school enrolment and moderate correspondence with the traditional wealth indicators of household expenditure in India, Indonesia, Pakistan and Nepal,
and with HIV prevalence in sub-Saharan Africa.
In the current study, among 1–4 year olds, while there was no association of overall mortality with dwelling characteristics, there was a trend towards lower mortality with increasing asset value (p
0.03). Separation into AIDS and non-AIDS mortality showed a clearer pattern, with high AIDS mortality in those with higher scoring dwellings, and high non-AIDS mortality in those with lower scoring dwellings and few assets.
For 1–4 year olds the pattern of deaths by household income source reflects the distribution of HIV in the population, with AIDS deaths dominating in households with employment, and non-AIDS deaths among those relying on subsistence farming. Higher HIV prevalence in wealthier adults (using quintiles derived from an asset-based wealth index) has been shown in DHS+ surveys from 8 countries in sub Saharan Africa, including in Malawi. 
There are no clear patterns for association with the household level measures for infants either overall or when divided into AIDS and non-AIDS mortality. This may reflect the greater difficulty of accurate assignment of cause of death as AIDS or non-AIDS in this age group. The sensitivity and specificity of verbal autopsy for the classification of infant and child AIDS deaths are poor,  
although better when, as here, the autopsy interview is carried out soon after death. 
The resulting misclassification is likely to have weakened the estimated effects of factors that had differential associations with AIDS and non-AIDS mortality. It is also possible that better-off HIV positive children are more likely to survive beyond infancy, reducing the association between socio-economic status and AIDS deaths in the infant age group, and magnifying it in the 1–4 year olds from the deferred deaths.
There was evidence that registration of births and deaths was near complete, from the re-census, from scheduled follow-ups of births after 1 year and from the distribution of ages at death. This makes it unlikely that child deaths were selectively missed (e.g. from poorer households and in remote areas). Parental and household characteristics were obtained by linking to other individuals in the study population. 95% of the mothers and 85% of the fathers of children below 5 years of age whose parents were not known to have died at baseline were among the population under surveillance, resulting in a high degree of completeness of information on parents. Asset score and main source of income were determined by interview, while dwelling construction was determined by direct observation by the field staff.
It is possible that other factors led to the lack of association between socio-economic status and child mortality. Differential migration could affect the trend if, for example, better off individuals stay in the district because of sickly children, but migration could affect all socio-economic levels.
The finding of the expected trends of higher non-AIDS mortality in children of households with few assets, poor dwelling construction, and relying on subsistence farming, suggests that the socio-economic indicators are measuring what they are supposed to measure. The lack of association with overall mortality is explained by the different trends in AIDS deaths. AIDS mortality was much higher in children from higher socio-economic status households, mirroring the distribution of HIV infection in the adult population. The usual and unwelcome gap in survival between the poor and the less poor has been lost, but because the less poor have been disproportionately affected by HIV, rather than because of relative improvement in the survival of the poorest.
Since HIV infection is associated with relative wealth in many parts of sub-Saharan Africa, 
a change in the distribution of child mortality is likely in other settings. The extent to which it is apparent will depend on the relative contribution of AIDS and non-AIDS deaths, so it is most likely in settings and age groups in which background mortality rates are low.
It is probably a temporary phenomenon. A shift in the distribution of HIV in the population towards the poorer individuals has been predicted, 
and a shift from the most educated groups earlier in the epidemic, to the less educated later, has been seen in several sub-Saharan African populations.
The survival gap is likely to return, and uneven access to antiretrovirals is likely to exacerbate the divide.