Establishment of Outbreak Thresholds for Hepatitis A in South Africa Using Laboratory Surveillance, 2017–2020

Nishi Prabdial-Sing,Villyen Motaze,Kerrigan McCarthy,Melinda Suchard,Jack Manamela

doi:10.3390/v13122470

Abstract

As South Africa transitions from endemic to intermediate endemicity, hepatitis A surveillance needs strengthening to monitor trends in disease incidence and to identify outbreaks. We used passive laboratory-based surveillance data from the National Health Laboratory Services to calculate national hepatitis A incidence and to establish thresholds for outbreaks. Incidence was calculated by age and geographic location. The static threshold used two or three standard deviations (SDs) above the mean hepatitis A incidence in 2017–2019, and a cumulative summation (CuSum2) threshold used three SDs above the mean of the preceding seven months. These thresholds were applied to hepatitis A data for 2020. From 2017 to 2020, the mean incidence of hepatitis A IgM was 4.06/100,000 and ranged from 4.23 to 4.85/100,000 per year. Hepatitis A incidence was highest in the Western Cape province (WCP) (7.00–10.92/100,000 per year). The highest incidence was in the 1–9-year-olds. The incidence of hepatitis A in 2020 exceeded the static threshold in two districts of the WCP: Cape Winelands in January and Overberg district in August. The provincial incidence did not exceed the static and CuSum2 thresholds. District-level analysis using either threshold was sensitive enough to monitor trends and to alert district health authorities, allowing early outbreak responses.

Highlights

Worldwide, 1.4 million people are affected with the hepatitis A virus (HAV) annually [1]
During the period 2017–2020, we identified 493,212 specimens submitted to National Health Laboratory Service (NHLS) laboratories for hepatitis A immunoglobulin M (IgM) testing, of which 13,914 were duplicates or had missing data, and were deleted from the analyses
The provincial incidence rate/100,000 population was highest in the Western Cape, and the Western Cape province had a relatively low testing rate/100,000 over the years, compared to the other provinces

Summary

Introduction

1.4 million people are affected with the hepatitis A virus (HAV) annually [1]. HAV causes acute disease of the liver, with clinical presentations ranging from asymptomatic to mild and occasionally severe. HAV is an enteric virus that is commonly spread through infected food and/or water. Hepatitis A prevalence is endemic in low- and middle-income countries, where clean sanitation and drinking water are lacking. Hepatitis A infection usually has a long incubation period of around 28 days (range 15–50 days) [2]. Serologic testing for hepatitis A immunoglobulin M (IgM) is required to confirm the diagnosis of an acute infection. Hepatitis A IgM can be detected 5–10 days before the onset of symptoms and can persist for up to 6 months [2]

Methods

Results

Conclusion