Intense and Mild First Epidemic Wave of Coronavirus Disease, The Gambia.

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic is evolving differently in Africa than in other regions. Africa has lower SARS-CoV-2 transmission rates and milder clinical manifestations. Detailed SARS-CoV-2 epidemiologic data are needed in Africa. We used publicly available data to calculate SARS-CoV-2 infections per 1,000 persons in The Gambia. We evaluated transmission rates among 1,366 employees of the Medical Research Council Unit The Gambia (MRCG), where systematic surveillance of symptomatic cases and contact tracing were implemented. By September 30, 2020, The Gambia had identified 3,579 SARS-CoV-2 cases, including 115 deaths; 67% of cases were identified in August. Among infections, MRCG staff accounted for 191 cases; all were asymptomatic or mild. The cumulative incidence rate among nonclinical MRCG staff was 124 infections/1,000 persons, which is >80-fold higher than estimates of diagnosed cases among the population. Systematic surveillance and seroepidemiologic surveys are needed to clarify the extent of SARS-CoV-2 transmission in Africa

Anchor Model-Based Hybrid Hierarchical Federated Learning with Overlap SGD

Federated learning (FL) is a distributed machine learning framework where multiple clients collaboratively train a model without sharing their data. Despite advancements, traditional FL methods encounter challenges including communication overhead, extended latency, and slow convergence. To address these issues, this paper introduces Anchor-HHFL, a novel approach that combines the strengths of synchronous and asynchronous FL. Anchor-HHFL employs multi-tier edge servers which conduct partial model aggregation and reduce the frequency of communication with the central server. Anchor-HHFL implements a novel divergence control method through hierarchical pullback. It orchestrates the sequence of each client\u27s stochastic gradient descent (SGD) updates to pull the locally trained models towards an anchor model, ensuring alignment and minimizing divergence. Simultaneously, a secondary process collects client models without disrupting their ongoing local computations and transmits them to edge servers, thereby overlapping computation with communication, substantially enhancing the training speed. Additionally, to effectively handle asynchronous updates across clusters, Anchor-HHFL uses a heuristic weight assignment for global aggregation, weighting clients\u27 updates based on the degree of their divergence from the global model. Extensive experiments on MNIST and CIFAR-10 datasets demonstrate Anchor-HHFL\u27s superiority, achieving up to $3 \times$ faster convergence and higher test accuracy compared to the baselines

Increased disease due to Haemophilus influenzae type b: population-based surveillance in eastern Gambia, 2008-2013.

BACKGROUND: In 1997, The Gambia became the first African country to introduce conjugate Haemophilus influenzae type b (Hib) vaccine with good disease control through to 2010. METHODS: Culture-based surveillance for invasive bacterial disease in eastern Gambia, specifically the Basse Health and Demographic Surveillance System (BHDSS) area, was conducted from 12 May 2008 and in Fuladu West district from 12 September 2011 until 31 December 2013. In 2011, Hib serology was measured in 5-34-year-olds. RESULTS: In all, 16,735 of 17,932 (93%) eligible patients were investigated. We detected 57 cases of invasive H. influenzae disease; 24 (42%) were type b. No cases of Hib disease were detected in the BHDSS area in 2008-2009; 1 was detected in 2010, 2 in 2011, 4 in 2012 and 7 in 2013. In 2013, the incidence of Hib disease in those aged 2-11 and 2-59 months in the BHDSS area was 88 [95% confidence interval (CI): 29-207] and 22 (95% CI: 9-45) cases per 10⁵ person-years, respectively. In 2013, disease incidence in Fuladu West among those aged 0-59 months was 26 (95% CI: 7-67) cases per 10⁵ person-years. Nine of 24 Hib cases were vaccine failures (2 HIV positive) and 9 were too young to have been vaccinated. The proportion of children aged 5-6 years (n = 223) with anti-Hib IgG ≥1.0 μg/mL was 67%; the antibody nadir was in 9-14-year-olds (n = 58) with 55% above threshold. CONCLUSIONS: Hib disease in eastern Gambia has increased in recent years. Surveillance in developing countries should remain alert to detect such changes