The novel coronavirus (COVID-19) pandemic is causing devastating demographic, social, and economic damage globally. Understanding current patterns of the pandemic spread and forecasting its long-term trajectory is essential in guiding policies aimed at curtailing the pandemic. This is particularly important in regions with weak economies and fragile health care systems such as West Africa. We formulate and use a deterministic compartmental model to (i) assess the current patterns of COVID-19 spread in West Africa, (ii) evaluate the impact of currently implemented control measures, and (iii) predict the future course of the pandemic with and without currently implemented and additional control measures in West Africa. An analytical expression for the threshold level of control measures (involving a reduction in the effective contact rate) required to curtail the pandemic is computed. Considering currently applied health control measures, numerical simulations of the model using baseline parameter values estimated from West African COVID-19 data project a 67% reduction in the daily number of cases when the epidemic attains its peak. More reduction in the number of cases will be achieved if additional public health control measures that result in a reduction in the effective contact rate are implemented. We found out that disease elimination is difficult when more asymptomatic individuals contribute in transmission or are not identified and isolated in a timely manner. However, maintaining a baseline level of asymptomatic isolation and a low transmission rate will lead to a significant reduction in the number of daily cases when the pandemic peaks. For example, at the baseline level of asymptomatic isolation, at least a 46% reduction in the transmission rate is required for disease elimination. Additionally, disease elimination is possible if asymptomatic individuals are identified and isolated within 5 days (after the incubation period). Combining two or more measures is better for disease control, e.g., if asymptomatic cases are contact traced or identified and isolated in less than 8 days, only about 29% reduction in the disease transmission rate is required for disease elimination. Furthermore, we showed that the currently implemented measures triggered a 33% reduction in the time-dependent effective reproduction number between February 28 and June 26, 2020. We conclude that curtailing the COVID-19 pandemic burden significantly in West Africa requires more control measures than those that have already been implemented, as well as more mass testing and contact tracing in order to identify and isolate asymptomatic individuals early.

新型冠状病毒 (COVID-19) 大流行正在全球范围内造成毁灭性的人口、社会和经济损失。了解当前流行病的传播模式并预测其长期轨迹对于指导旨在遏制该流行病的政策至关重要。这对于西非等经济疲软、医疗保健系统脆弱的地区尤其重要。我们制定并使用确定性分区模型来 (i) 评估 COVID-19 在西非的当前传播模式，(ii) 评估当前实施的控制措施的影响，以及 (iii) 预测大流行的未来进程西非目前没有实施额外的控制措施。计算遏制大流行所需的控制措施阈值水平（包括有效接触率的降低）的分析表达式。考虑到目前采用的健康控制措施，使用根据西非 COVID-19 数据估计的基线参数值对模型进行数值模拟，预计当疫情达到顶峰时，每日病例数将减少 67%。如果采取额外的公共卫生控制措施，降低有效接触率，将进一步减少病例数量。我们发现，当更多无症状个体参与传播或未及时识别和隔离时，消除疾病就很困难。然而，维持无症状隔离的基线水平和低传播率将导致疫情高峰时每日病例数大幅减少。 例如，在无症状隔离的基线水平上，传播率至少需要降低46%才能消除疾病。此外，如果在 5 天内（潜伏期后）识别并隔离无症状个体，则有可能消除疾病。将两种或多种措施结合起来对疾病控制效果更好，例如，如果在8天内追踪或识别并隔离无症状病例，只需将疾病传播率降低约29%即可消除疾病。此外，我们发现，目前实施的措施导致 2020 年 2 月 28 日至 6 月 26 日期间随时间变化的有效繁殖数减少了 33%。我们的结论是，要显着减少西非的 COVID-19 大流行负担，需要采取比采取更多控制措施那些已经实施的措施，以及更多的大规模检测和接触者追踪，以便及早识别和隔离无症状个体。