ABSTRACT
In this paper, we aim to build and study a stochastic SEIRS model with vaccination in which we consider two types of infected: undetected and confirmed. The latter are hospitalized and receive treatment. We also derive the Hamilton Jacobi Bellman (HJB) equation by using dynamic programming tools, and we study it from theoretical and numerical points of view. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.
ABSTRACT
This paper provides an early assessment of the effects of the COVID-19 outbreak and of subsequent response measures on milk production, collection, processing, marketing and consumption in Africa. The researchers focus on the period surrounding the first wave of the outbreak (from February to June 2020), during which the number of cases surged and many steps were taken to curb the epidemic. The paper is based on reports from four countries covered by the Africa-Milk Research Project: Burkina Faso, Kenya, Madagascar and Senegal. Data was collected primarily from nine dairy processors located in those countries. Major conclusions of the study are: (1) Dairy farmers were negatively affected by COVID-19 measures when the health crisis coincided with the peak of the milk production season, and when governments did not take steps to support milk production. (2) Small and informal milk collectors were also affected by traffic restrictions as they could not obtain traffic permits. (3) Milk powder importation remained unaffected during the outbreak. (4) Dairy processors (particularly small ones) faced many challenges restricting their operation. Travel restrictions led to temporary interruptions of milk supply, and because of employee protection and safety measures, processing costs increased. (5) Many small retailers were affected by bans on public transport and reduced their purchases of artisanal dairy products;meanwhile, spoilage of dairy products increased during long curfews coupled with poor storage conditions. Supermarkets were able to increase their market share during the pandemic thanks to their connections with industrial dairy processors and wholesalers. (6) A majority of consumers decreased their consumption of dairy products due to a decrease of purchasing power. In some cases, an increase in consumption occurred (due to Ramadan month and dry season high temperatures) and consumption shifted towards long-life dairy products. (7) Overall, the consequences of the health crisis affected more small and informal dairy supply chains than the larger ones, which are more formal, better organised and finally more resilient to face this kind of global crisis.