Time to control of anthrax outbreaks in Africa, 2014-2023: A systematic review and meta-analysis

Anthrax is a notifiable zoonotic disease targeted for control in Africa, however, outbreaks due to anthrax are still frequent and large. Surveillance systems should monitor and detect anthrax outbreaks early for prompt response. This systematic review and meta-analysis aimed to determine anthrax outbreaks epidemiological investigations gaps and time to control in Africa, Jan 2014-Dec 2023. We searched MEDLINE, PubMed, Scopus, Embase, Google Scholar, and Web of Science databases using PICO framework for studies on anthrax investigations. Using Covidence, we screened and extracted studies, analysed descriptive data using Microsoft Excel and quantitative data using RStudio version 4.3.1. We calculated heterogeneity and confidence intervals around pooled effect and performed risk of bias assessment. Ten of 1,639 studies met eligibility criteria and were included. Pooled median duration to control was 40.5 (IQR 80.8) days and estimated duration of outbreak end was 59.2 days (95% CI: 7.4-111.0), far beyond two incubation periods of anthrax (14 days). Median time to alert was 5 days (95% CI:0-490). A third (30%) didn't investigate animal anthrax. No study reported use of all levels of case definitions, and no study translated case investigation forms into local languages. A third (30%) of studies omitted time component of descriptive epidemiology and 22% of studies used cross-sectional study design. All studies used epidemiologists for case investigations, with 90% employing field epidemiologists, only one study used a social worker. Only 20% of studies used government funds; majority (80%) instituted public health actions. Risk of bias was at 0-20%. Median duration to control was greater than two anthrax incubation periods indicating delayed response. Several epidemiological gaps including delayed outbreak verification, focus on human anthrax and neglect of zoonotic aspects, and inappropriate working case definitions were highlighted. Timely and comprehensive epidemiological investigations, with a One Health approach to anthrax outbreak control is recommended. Systematic Review Registration: The protocol that guided this review was registered on PROSPERO: CRD42024498034.