An early epidemiological report
from Wuhan, China on the outbreak of coronavirus-related pneumonia provided important details about the transmission of SARS-CoV-2 and suggested the means to confine its spread. This is according to health experts including Anthony Fauci, MD, director of the National Institutes of Allergy and Infectious Diseases (NIAID) and Robert Redfield, MD, director of the US Centers for Disease Control and Prevention, in recently published commentary
that accompanied the report.
The analysis of data from the first 425 patients with laboratory confirmed coronavirus-infected pneumonia in Wuhan, China was conducted by Qun Li, M Med, Chinese Center for Disease Control and Prevention, Bejing, China, and colleagues. They were able to gather information on demographic characteristics, exposure history, and illness timelines for the patients who were identified through January 22nd.
"On the basis of this information, there is evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019," Li and colleagues wrote.
The researchers had determined that the mean incubation period was 5.2 days, with the 95th percentile of the distribution at 12.5 days. They found that in its early stages, the epidemic doubled in size every 7.4 days. With a mean serial interval of 7.5 days, they estimated that the basic reproductive number from each infected individual was to 2.2 other persons.
In commentary, written contemporaneously with the report and preceding progression to full pandemic, Fauci and Redfield, with Clifford Lane, MD, a deputy director at NIAID, acknowledged the difficulty the researchers met in trying to analyze the event as it unfolded.
"Although this information is critical in informing the appropriate response to this outbreak, as the authors point out, the study faces the limitation associated with reporting in real time the evolution of an emerging pathogen in its earliest stages," Fauci, Lane and Redfield pointed out.
They noted that estimations of mortality were drawn from the case definitions requiring diagnosis of pneumonia. The report, then, also left the extrapolation of transmission by asymptomatic or minimally symptomatic cases to be elucidated. Fauci and colleagues pointed to other findings at the time, including high titers of virus in the oropharynx early in the course of disease, that were potential indicators of increased infectivity during periods of minimal symptoms—and which have subsequently been confirmed in the pandemic experience.
In noting that the epidemiologists determined a mean interval of 9.1 to 12.5 days between the onset of illness and hospitalization, Fauci and colleagues suggested this delay in the progression to serious disease could reflect important aspects about the pathogenesis, and provide "a unique window of opportunity for intervention."
"Every outbreak provides an opportunity to gain important information, some of which is associated with a limited window of opportunity," indicated Fauci, Redfield and Lane.
Marc Lipsitch, DPhil, Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, MA, and colleagues elaborated
, in another commentary published concurrently with the report by Li et al, on the types of ongoing epidemiologic studies and support measures that are necessary to refine remediation efforts.
"Now is the time to put in place the infrastructure to accomplish such surveillance," Lipsitch and colleagues urged, in writing that predated the pandemic.
They emphasized the importance of evaluating data from simultaneous surveillance studies, epidemiologic field investigations, and case series. Prior to the current imposition of social distancing, Lipsitch and colleagues had argued for conducting cohort studies in settings such as schools, workplaces, and neighborhoods, to help describe the overall burden and the household and community attack rates.
"Early investments in characterizing SARS-CoV-2 will pay off handsomely in improving the epidemic response," Lipsitch and colleagues indicated—in advice that may have been outpaced by current events but that can still inform approaches to stave off future surges and confront other outbreaks.
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