Establishment of outbreak thresholds for Hepatitis A in South Africa using laboratory surveillance, 2017–2020

Prabdial-Sing, Nishi ; Motaze, Nkengafac Villyen ; Manamela, Jack ; McCarthy, Kerrigan ; Suchard, Melinda (2021)

CITATION: Prabdial-Sing, N. et al. 2021. Establishment of outbreak thresholds for Hepatitis A in South Africa using laboratory surveillance, 2017–2020. Viruses, 13:2470, doi:10.3390/v13122470.

The original publication is available at https://www.mdpi.com

Article

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.

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