National estimates of HIV trends in generalized epidemics
rely on HIV prevalence data from antenatal clinic (ANC) surveillance. We
investigate whether HIV prevalence trends in ANC data reflect trends in men and
women in the general population during the scale-up of antiretroviral therapy
(ART) in Manicaland, Zimbabwe.
Trends in HIV prevalence in local ANC attendees and adults
aged 15-49 years in towns, agricultural estates, and villages were compared
using five rounds of parallel ANC (N = 1200) and general-population surveys (N
= 10 000) and multivariable log-linear regression. Changes in the age pattern
of HIV prevalence and the age distribution of ANC attendees were compared with
those in the general population. Age-specific pregnancy prevalence rates were
compared by HIV infection and ART status.
Cumulatively, from 1998-2000 to 2009-2011, HIV prevalence
fell by 60.0% in ANC surveillance data
and by 34.3% (30.8-37.7%) in the general population. Most of the difference
arose following the introduction of ART (2006-2011). The estates and villages
reflected this overall pattern but HIV prevalence in the towns was lower at
local ANCs than in the general population, largely because of attendance by
pregnant women from outlying (lower prevalence) areas. The ageing of people
living with HIV in the general population (52.4% aged >35 years, 2009-2011)
was under-represented in the ANC data (12.6%) because of lower fertility in
older and HIV-infected women.
After the introduction of ART in Manicaland, HIV prevalence
declined more steeply in ANC surveillance data than in the general population.
Models used for HIV estimates must reflect this change in bias.
- 1aDepartment of Infectious Disease Epidemiology, Imperial College London School of Public Health, London, United Kingdom bBiomedical Research and Training Institute cAIDS and TB Unit, Zimbabwe Ministry of Health and Child Welfare, Harare, Zimbabwe.
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