Research Article: Hepatitis A virus seroprevalence in South Africa – Estimates using routine laboratory data, 2005–2015

Date Published: June 26, 2019

Publisher: Public Library of Science

Author(s): Ahmad Haeri Mazanderani, Nkengafac Villyen Motaze, Kerrigan McCarthy, Melinda Suchard, Nicolette Marie du Plessis, Yury E. Khudyakov.

http://doi.org/10.1371/journal.pone.0216033

Abstract

South Africa is considered highly endemic for hepatitis A virus (HAV) although few seroprevalence studies have been conducted over the past two decades. The World Health Organization recommends integrating HAV vaccination into national childhood immunization schedules where there is transition from high to intermediate endemicity. As a means of gauging age-specific rates of infection, we report HAV seroprevalence rates among specimens tested for HAV serology within South Africa’s public health sector from 2005–2015.

Hepatitis A serology results (Anti-HAV IgM, IgG and total antibody) from 2005–2015 were extracted from South Africa’s National Health Laboratory Service’s Corporate Data Warehouse (NHLS CDW), the central data repository of all laboratory test-sets within the public health sector. Results were extracted according to test-set, result, date of testing, health facility, name, surname, age, and sex. Anti-HAV IgG results were merged with total antibody results to reflect anti-HAV seroprevalence. Testing volume, positivity rates and age-specific anti-HAV seroprevalence rates by year and geographic distribution are described.

A total of 501 083 HAV IgM results were retrieved, of which 16 423 (3.3%) were positive, 484 259 (96.6%) negative and 401 (0.1%) equivocal; and 34 710 HAV total antibody/IgG tests of which 30 675 (88.4%) were positive, 4 020 (11.6%) negative and 15 equivocal. Whereas IgM positivity was highest among the 1–4 year age group (33.5%) and lowest among patients >45 years (<0.5%), total antibody positivity ranged from its lowest level of 52.7% in the 1–4 year age group increasing to levels of >90% only after 25 years of age.

Anti-HAV total antibody testing within the South African public health sector demonstrates seroprevalence rates reach levels >90% only in adulthood, suggesting South Africa could be in transition from high to intermediate endemicity. Prospective studies with geographically representative sampling are required to confirm these findings and evaluate provincial and urban/rural heterogeneity.

Partial Text

Hepatitis A viral (HAV) infection is the leading cause of viral hepatitis globally [1]. It is usually transmitted via the faecal/oral route through ingestion of contaminated food or water. Whereas exposure to HAV during early childhood is predominantly associated with asymptomatic infection, older children and adults often experience symptomatic disease; with increasing severity associated with increasing age.(1) Unlike hepatitis B or C viral infection, HAV disease is usually self-limiting and not associated with chronicity, it is nevertheless associated with considerable economic burden [2].

This was a cross-sectional descriptive study of routine laboratory data from the South African public health sector from 2005 to 2015. All anti-HAV serology results (IgM, IgG and total antibody) were extracted from the National Health Laboratory Service’s Corporate Data Warehouse (NHLS CDW), the central data repository of laboratory results within the public health sector in South Africa. Results were extracted according to test-set, qualitative result, date of testing, health facility, and patient demographic details, including name, surname, age, and sex. Each test episode was assigned a unique numerical identifier generated from the patient demographic details after which patient name and surname were deleted prior to analysis.

From 1 January 2005 to 31 December 2015 a total 523 393 specimens registered for HAV serology were retrieved from the NHLS data warehouse. Of the 520 847 registered specimens that met the inclusion criteria, 501 083 were anti-HAV IgM results (459 992 with a registered age or date of birth) and 34 710 anti-HAV total antibody results (31 160 with a registered age or date of birth). A total of 14 946 specimens had both anti-HAV IgM and total antibody test results.

This study represents the largest description of HAV seroprevalence within South Africa to date. Using routine laboratory data, hepatitis A testing patterns, acute infection and seropositivity rates within the public health sector are described and the level of endemicity gauged.

A number of important limitations exist regarding this study. Data from NHLS CDW was used which reflects testing practices within the South African public health sector only. This analysis may therefore not necessarily reflect the population as a whole as more affluent sectors of South African society would not have been included. Approximately 20% of the South African population engage with the private health sector [15], and this component of the population is likely to have a much lower infection rate as a result of private vaccination practice and better living conditions. When infection does occur within the private sector, it is likely to arise at an older age with a greater proportion of infections associated with symptomatic disease. It is important to note that clinical data, including patient socio-economic status, is not captured within the NHLS CDW thereby precluding a description of these variables and their association with HAV seroprevalence within the South African public health sector.

 

Source:

http://doi.org/10.1371/journal.pone.0216033

 

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