Molecular characterization of an outbreak-involved Bacillus anthracis strain confirms the spillover of anthrax from West Africa.

BACKGROUND: Anthrax, a zoonotic disease caused by the spore-forming bacterium Bacillus anthracis, remains a major global public health concern, especially in countries with limited resources. Sierra Leone, a West African country historically plagued by anthrax, has almost been out of report on this disease in recent decades. In this study, we described a large-scale anthrax outbreak affecting both animals and humans and attempted to characterize the pathogen using molecular techniques. METHODS: The causative agent of the animal outbreak in Port Loko District, Sierra Leone, between March and May 2022 was identified using the nanopore sequencing technique. A nationwide active surveillance was implemented from May 2022 to June 2023 to monitor the occurrence of anthrax-specific symptoms in humans. Suspected cases were subsequently verified using quantitative polymerase chain reaction. Full-genome sequencing was accomplished by combining long-read and short-read sequencing methods. Subsequent phylogenetic analysis was performed based on the full-chromosome single nucleotide polymorphisms. RESULTS: The outbreak in Port Loko District, Sierra Leone, led to the death of 233 animals between March 26th and May 16th, 2022. We ruled out the initial suspicion of Anaplasma species and successfully identified B. anthracis as the causative agent of the outbreak. As a result of the government's prompt response, out of the 49 suspected human cases identified during the one-year active surveillance, only 6 human cases tested positive, all within the first month after the official declaration of the outbreak. The phylogenetic analysis indicated that the BaSL2022 isolate responsible for the outbreak was positioned in the A.Br.153 clade within the TransEuroAsian group of B. anthracis. CONCLUSIONS: We successfully identified a large-scale anthrax outbreak in Sierra Leone. The causative isolate of B. anthracis, BaSL2022, phylogenetically bridged other lineages in A.Br.153 clade and neighboring genetic groups, A.Br.144 and A.Br.148, eventually confirming the spillover of anthrax from West Africa. Given the wide dissemination of B. anthracis spores, it is highly advisable to effectively monitor the potential reoccurrence of anthrax outbreaks and to launch campaigns to improve public awareness regarding anthrax in Sierra Leone.

Cost Analysis of Health Facility Electronic Integrated Disease Surveillance and Response in One District in Sierra Leone.

Global health security depends on effective surveillance systems to prevent, detect, and respond to disease threats. Real-time surveillance initiatives aim to develop electronic systems to improve reporting and analysis of disease data. Sierra Leone, with the support of Global Health Security Agenda partners, developed an electronic Integrated Disease Surveillance and Response (eIDSR) system capable of mobile reporting from health facilities. We estimated the economic costs associated with rollout of health facility eIDSR in the Western Area Rural district in Sierra Leone and projected annual direct operational costs. Cost scenarios with increased transport costs, decreased use of partner personnel, and altered cellular data costs were modeled. Cost data associated with activities were retrospectively collected and were assessed across rollout phases. Costs were organized into cost categories: personnel, office operating, transport, and capital. We estimated costs by category and phase and calculated per health facility and per capita costs. The total economic cost to roll out eIDSR to the Western Area Rural district over the 14-week period was US$64,342, a per health facility cost of $1,021. Equipment for eIDSR was the primary cost driver (45.5%), followed by personnel (35.2%). Direct rollout costs were $38,059, or 59.2% of total economic costs. The projected annual direct operational costs were $14,091, or $224 per health facility. Although eIDSR equipment costs are a large portion of total costs, annual direct operational costs are projected to be minimal once the system is implemented. Our findings can be used to make decisions about establishing and maintaining electronic, real-time surveillance in Sierra Leone and other low-resource settings.