Source: Data from European Centre for Disease Prevention and Control. Note: 7 days moving average.
The onset of the COVID-19 pandemic in 2020 can be represented as four major waves, all of which are illustrative of the diffusion cycle of a pandemic.
- First wave (supply shocks). Credible evidence underlines that the COVID-19 pandemic emerged in Wuhan, China, in late 2019. By early 2020, it has diffused throughout the city and spread across several major Chinese cities. It also started to be recognized as a threat to global health, particularly after national shutdowns measures were initiated in late January, with cities such as Wuhan completely quarantined. This had substantial impacts on Chinese manufacturing capabilities and the related supply chains. By late February, it was looking like the situation was improving as lockdown measures were lifted and manufacturing activities gradually resumed. During this period (late February to mid-March 2020), even if it was realized afterward that the coronavirus was undertaking a phase of translocation from China to Europe and the United States (which in the next wave became the most impacted regions). The United States and many other countries instituted travel bans on China in early February. Still, bans between the United States and Europe were implemented in mid-March after it was realized that Europe (particularly Italy and Spain) was becoming the main source of translocation. The lack of testing capabilities undermined the realization that a pandemic was quickly unfolding, with its scale and extent not yet apparent. Adjacent countries to China, namely South Korea, Taiwan, Hong Kong, SAR, and Japan, reported a surge in cases and quickly implemented quarantine measures. Outbreaks were reported on several cruise ships that called Chinese ports (or had a large number of Chinese passengers), such as the Diamond Princess (712 cases reported out of a manifest of 3,700 passengers and crew, including 13 deaths). This resulted in the shutdown of the global cruise industry by mid-march, as global air travel collapsed.
- Second wave (demand shocks). By early March 2020, a surge in the number of cases was reported in Italy and Spain, quickly followed by the United States. It became apparent that during the “stealth phase”, the coronavirus had translocated in almost all advanced economies and that the virus was now diffusing among local populations. The source of contamination could no longer be traced to an external event such as traveling abroad, as was the case for most early infections. On March 11, 2020, COVID-19 was officially declared a pandemic. Lockdowns were instituted with the bulk of the population ordered to remain home, creating a surge in unemployment, the collapse of travel and tourism, and most aspects of manufacturing and retailing. The demand for non-essential goods, including energy, declined substantially. Demand surges for groceries, personal items, home furniture, and medical equipment stressed the related supply chains through demand shocks. From mid-April 2020, the number of reported cases in advanced economies gradually declined, partly attributed to lockdown and quarantine measures. With the decline of reported new cases, several economies began to resume normal economic activities. However, the pandemic shifted to previously relatively unimpacted areas, likely because of the lack of testing. Russia, Brazil, and India experienced by early May 2020 a surge of reported cases, in line with what happened in Europe and the United States in early March 2020. Due to the lack of testing and reporting, little is known about the extent of the pandemic in many parts of Sub-Saharan Africa and South Asia.
- Third wave (adaption). From June 2020, most advanced economies were back to operations under social distancing measures. Several major developing economies were at their peak level of diffusion. For instance, in early July 2020, Latin American countries, including Brazil, surpassed the United States in the number of reported cases. Further, the United States saw a significant second wave of infections in part because of social unrest placed millions in close proximity and inappropriate social distancing once activities were reopened. Demand patterns began to shift as demand deferred during the lockdowns resumed and stimulus packages were implemented.
- Fourth wave (resurgence). By the summer of 2020, while the social and economic adaptation to the pandemic was underway, the pandemic continued its diffusion, with reported cases rising. Global supply chains resumed, and traffic along shipping lanes and ports picked up. This process continued in the later part of 2020 and was the precursor to the supply chain crisis that unfolded in 2021 and 2022.