## 1 Introduction  
A supply chain (SC) is \"the network of organizations that are involved, through upstream and downstream linkages, in the different processes and activities that produce value in the form of products and services delivered to the ultimate consumer\" [1]. Because the SC includes different stages, such as procurement, manufacturing, distribution, waste disposal and all the activity associated with transport, storage and information technology (IT) [2], and it is crucial that any connection works well to ensure the efficiency of the chain [3], the management of the SC is clearly a complex task. To describe this activity, the concept of Supply Chain Management (SCM) has been introduced. The definition of SCM seems to be less common across authors than the definition of SC. According to [PERSON] and [PERSON] [4], \"supply chain management deals with the total flow of materials from suppliers through end users...\" and its objective \"is to integrate and manage the sourcing, flow, and control of materials using a total systems perspective across multiple functions and multiple tiers of suppliers\" [5]. In addition to the inherently complex management of the SC, its equilibrium can be undermined by a variety of factors, named \"disturbances\", which range from human errors to fluctuating demand, from the outbreak of war to the outbreak of a pandemic emergency. In December 2019, a virus previously unknown, later named COVID-19 [6], was identified in Wuhan, China and the World Health Organization (WHO) declared it a pandemic on March 11, 2020. Due to the rapid and global spread of the virus, coupled with high mortality rate, first the Chinese government, and then governments worldwide, implemented restrictive measures that impacted on the population and companies. Precautionary measures included social distancing, introduction of personal protective equipment and restrictions on travel and work activities; hence, companies were forced to stop their activities or to quickly adapt to the evolving changes [7]. These measures, especially those related to production facilities and the movement of goods between borders caused delays in deliveries [7; 8], resulting in negative impacts on trade, transportation, production, and all stages that constitute the SC. Due to its unpredictability, devastating impact [9], high uncertainty, and long duration of effects [10], the COVID-19 pandemic has been termed a \"black swan\". It has also led to economic disruptions around the world by interrupting all SCs, both those aimed at selling products and those aimed at delivering services [11], forcing them to deal with a situation which was out of the ordinary. Due to simultaneous disruptions in demand, supply, and logistics infrastructures, with concurrent and/or sequential openings and closures of suppliers, factories, and markets [12], SCs have been exposed to several risks, which have contributed to the instability of the moment. According to [13], SC risk \"should refer to (i) events with small probability but may occur abruptly and (ii) these events bring substantial negative consequences to the system\". As such, risk includes any stage of supply, production and delivery (material flow risk), investments and/or inability to settle payments (financial flow risk), security issues and accuracy of information (information flow risk) [14]. During the COVID-19 pandemic, the risk related to material flow particularly increased, due to blockages and restrictions affecting production and logistics in several countries. Examples are blockages caused by suppliers' production interruptions or reduction in their output due to labor shortages. Transportation-related blockades also severely affected the supply of materials. An example of these situations occurred in Wuhan, in a production center for automobile parts for companies such as Toyota and Volkswagen. It is inevitable that at the early stages of the pandemic, companies that had key suppliers in Wuhan were disadvantaged.