Dissecting the early COVID-19 cases in Wuhan

Source: Science Magazine

Some key questions lie at the heart of investigations into the origin of the COVID-19 pandemic, including what is known about the earliest COVID-19 cases in Wuhan, China, and what can be learned from them? Despite assertions to the contrary (1), it is now clear that live mammals susceptible to coronaviruses, including raccoon dogs (Nyctereutes procyonoides), were sold at Huanan Market and three other live-animal markets in Wuhan before the pandemic (2, 3). Severe acute respiratory syndrome–related coronaviruses (SARSr-CoVs) were found in raccoon dogs during the SARS outbreak, which was facilitated by animal-to-human contact in live-animal markets in China. However, because of the early public health focus on Huanan Market, it remains unclear whether the apparent preponderance of hospitalized COVID-19 cases associated with this market was truly reflective of the initial outbreak. Answering these questions requires resolving several crucial events that took place in December 2019 and early January 2020.

On 30 December 2019, the Wuhan Municipal Health Commission (WHC) issued two emergency notices for internal circulation to local hospitals alerting them to patients with unexplained pneumonia—several of whom worked at Huanan Market—and laying out a treatment and response plan (see fig. S1). The first official public report was WHC’s announcement the next day that they had carried out case searches and retrospective investigations related to Huanan Market and found 27 patients. Forty-one of the first known patients formed the basis of an influential study that reported that 66%—i.e., not all early cases—had a link to Huanan Market (4). They had been transferred between 29 December and 2 January from other hospitals to Jinyintan Hospital, Wuhan’s premier infectious disease center. Notably, individuals were enrolled according to clinical presentation, not epidemiologic information, such as connections to Huanan Market (4).

China’s Viral Pneumonia of Unknown Etiology (VPUE) mechanism was set up in the wake of SARS to be an early warning reporting system for detecting unknown viral diseases and is overseen by the China Center for Disease Control and Prevention (CCDC) (5). PUE cases are supposed to be rapidly reported by clinicians to the national notifiable disease reporting system through an internet-based platform. Evidently, that did not happen in Wuhan in December. The system appears to have been in active use only from 3 January. Although it favored cases having a connection to Huanan Market (6–8), the VPUE mechanism could not have improperly inflated the proportion of Huanan Market–linked cases in December (1). Moreover, reporting began only after the 41 patients were transferred from other hospitals to Jinyintan Hospital. Nevertheless, it is possible that a disproportionate number of cases linked to Huanan Market were transferred to Jinyintan Hospital because of public health officials’ early focus there.



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